[mike@mwxm4]

Changing what a machine has: vCPUs and memory, in the action menu as c and m,
and on the command line as `gvm size`.

resize.go holds the rules, in the shape power.go uses — one objection function
in two lengths, so the menu's grey-out and the message cannot disagree:

* A running machine can only grow, and only where it was built to: CPU and
  memory hot-add are per-machine settings. Memory can never shrink while it
  runs (vSphere has no memory hot-remove) and vCPUs only with hot-remove on.
* The vCPU count must be a multiple of the cores per socket. The socket
  topology is never changed to make a number fit — that would rewrite somebody's
  per-socket licence — so the two counts that do fit are named instead.
* Memory is typed in GB (512m for MB) and must be whole multiples of 4 MB.
* The configuration is read again immediately before anything is sent: the
  menu's grey-out only says a change of this kind is possible at all.

The four config fields are not in the sweep — config is the machine's whole
configuration document — so they are read for one machine when the menu opens
and again when the change is made.

Nothing here loses anything, so it gets the plain y/n question, not the page
that wants YES typed: that one stays for pulling the plug, reverting and
removing snapshots.

`gvm size --vm <machine>` with no number changes nothing and prints what the
machine has, including which of the three hot-plug settings it was built with —
the line that decides whether a change needs a maintenance window.

Tests: the objection matrix (off/running × grow/shrink × settings), the socket
rule, the pointer handling in sizingFrom, what parseSize takes and refuses, the
menu entries, and against the simulator a real ReconfigVM whose numbers are read
back from the server rather than assumed.

.gitignore gains .claude/, which is the agent harness's scratch directory.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -15,3 +15,4 @@ bin/
 tmp/
 gvm
 .gvmrc
+.claude/

README.md

@@ -97,6 +97,8 @@ not.
 | `power -b <vm>` | ask the guest to reboot (needs VMware Tools) |
 | `power --off <vm>` | power off at the hypervisor — hard |
 | `power --reset <vm>` | reset at the hypervisor — hard |
+| `size --vm <vm>` | what it has: vCPUs, memory, and what may be changed while it runs |
+| `size --vm <vm> -c 8 -m 16` | give it 8 vCPUs and 16 GB — `-m 512m` for megabytes |
 | `host [-t]` | per-host cpu, memory, machine counts; `-t` also posts them |
 | `host -c` | just the machine counts |
 | `ds [-t]` | per-datastore capacity, free space, over-commitment; `-t` also posts them |
@@ -372,12 +374,18 @@ this is about.
     r  revert to a snapshot ...            s  shut down the guest
     d  remove a snapshot ...               b  reboot the guest
     D  remove ALL snapshots                S  power off  (hard)
-                                           B  reset      (hard)
+    ────────────────────────────────       B  reset      (hard)
+    c  change the vCPU count ...
+    m  change the memory ...
 
-Lowercase asks the guest, uppercase acts at the hypervisor: the violent variant
-always needs the shift key. What cannot be done right now is greyed out with the
-reason next to it — "no VMware Tools", "already running", "no snapshots" — rather
-than left out, and picking it anyway spells the reason out instead of running it.
+Of the power pairs, lowercase asks the guest and uppercase acts at the
+hypervisor: the violent variant always needs the shift key. What cannot be done
+right now is greyed out with the reason next to it — "no VMware Tools", "already
+running", "no snapshots", "needs it off" — rather than left out, and picking it
+anyway spells the reason out instead of running it.
+
+The three groups are what the machine has been, what it is, and what it is
+doing.
 
 Snapshots are drawn as the tree they are — which state descends from which is
 the whole point of a snapshot list — and the one the machine is running from
@@ -455,6 +463,48 @@ things hold for all of them:
 One power operation per command line; two is a mistake, not a sequence, and gvm
 says so instead of guessing.
 
+### What a machine has
+
+`c` and `m` in the menu, `gvm size` on the command line: the vCPU count and the
+memory. Nothing is lost by either, so they get the plain y/n question rather than
+the page that wants YES typed out — a number set wrongly is set back.
+
+vSphere refuses most of what one might ask for on a running machine, and gvm
+refuses it first, with the reason, rather than sending it to be bounced:
+
+* **A running machine can only grow, and only where it was built to.** CPU and
+  memory hot-add are per-machine settings, turned on when the machine was made.
+  Without them the entry says "needs it off". Memory can never shrink while a
+  machine runs — there is no hot-remove for it in vSphere at all — and vCPUs only
+  where hot-remove is on as well.
+* **The socket topology is the machine's own.** A vCPU count has to be a multiple
+  of the cores per socket, and gvm does not quietly change the sockets to make a
+  number fit: software is licensed per socket, and a tool that turns 2 sockets
+  into 4 to accept an odd number would be writing somebody an invoice. It names
+  the two counts that do fit instead.
+* **Memory is whole multiples of 4 MB.** It is typed in gigabytes, because that
+  is what the sheet shows and what anybody says out loud; `512m` means megabytes,
+  and `1.5g` is 1536 MB.
+* **Read again immediately before it is sent.** The menu's grey-out says only
+  that a change of this kind is possible at all; between drawing it and answering
+  the question somebody else may have started the machine.
+
+`gvm size --vm <machine>` on its own changes nothing and says what there is:
+
+    machine        web01  (running)
+    vCPU           4, in 1 per socket
+    memory         8.0GB
+    while it runs  add vCPUs, add memory
+
+That last line is the one worth having before planning the work — it is the
+difference between a change now and a maintenance window. Where a machine has
+none of the three settings it says so plainly: "nothing — it has to be powered
+off to be changed".
+
+Hot-added resources are not necessarily in use the moment vCenter reports the
+task done: the message says as much, because an operating system does not always
+notice on its own that it has been given another four processors.
+
 The printed listing (`vm -l`) is the same table: the same columns, the same
 cells, the same colours, fitted to the terminal when there is one and written out
 in full into a pipe, where the colours are left off.
@@ -716,6 +766,10 @@ wrong quietly:
 * that `y` names what it copied and that an ssh login uses no local clipboard
   tool — the tests say they are a login, which also keeps them off the clipboard
   of whoever is running them
+* every rule a resize is held to: what a running machine may and may not be
+  given, that the cores per socket are never changed to make a vCPU count fit,
+  and — against the simulator — that a reconfigure actually lands, read back
+  from the server rather than assumed
 * that a `^C` during a login does not take gvm with it, and that the login still
   dies of it: the signal is caught for as long as the child has the screen, and
   catching is not ignoring — an ignored one would be inherited by the ssh

actions.go

@@ -147,7 +147,18 @@ func (b *browser) openMenu() {
 		return
 	}
 	b.menuSnaps = snaps
-	b.menu = b.buildMenu(*r, snaps)
+
+	// What the machine has, and what of it may be changed while it runs. It is
+	// not in the sweep — it is four fields of the whole configuration document
+	// — so it is read here, for this one machine, and only so that the two
+	// hardware entries can be greyed out with the reason rather than accepting
+	// a number vCenter is going to refuse. A failure is not fatal: the entries
+	// are offered and the server has the last word.
+	b.menuSize, err = sizingOf(r.sess, r.ref)
+	if err != nil {
+		b.setStatus(colWarn, err.Error())
+	}
+	b.menu = b.buildMenu(*r, snaps, b.menuSize)
 	// vmDetail asks nothing of the network; the snapshots are left out of it
 	// because the menu only wants the four lines above.
 	b.menuInfo = sheetPick(vmDetail(*r, nil, ""), menuFacts)
@@ -160,7 +171,7 @@ func (b *browser) closeMenu() {
 }
 
 // buildMenu is the menu for one machine in its current state.
-func (b *browser) buildMenu(r vmRow, snaps []snapEntry) []menuItem {
+func (b *browser) buildMenu(r vmRow, snaps []snapEntry, sz sizing) []menuItem {
 	noSnaps, noSnapsHint := "", ""
 	if len(snaps) == 0 {
 		noSnaps, noSnapsHint = "the machine has no snapshots", "no snapshots"
@@ -184,6 +195,12 @@ func (b *browser) buildMenu(r vmRow, snaps []snapEntry) []menuItem {
 		{key: 'D', label: "remove ALL snapshots", why: noSnaps, hint: noSnapsHint,
 			run: func(b *browser, r vmRow) { b.removeAll(r, len(snaps)) }},
 		separator(),
+		// What the machine is, between what it has been and what it is doing.
+		// Both entries end in "..." for the same reason the snapshot ones do:
+		// they ask for something before anything happens.
+		sizeItem('c', "change the vCPU count ...", r, sz, sizeCPUs),
+		sizeItem('m', "change the memory ...", r, sz, sizeMemory),
+		separator(),
 		pwr('o', "power on", opPowerOn),
 		pwr('s', "shut down the guest", opShutdownGuest),
 		pwr('b', "reboot the guest", opRebootGuest),
@@ -193,6 +210,16 @@ func (b *browser) buildMenu(r vmRow, snaps []snapEntry) []menuItem {
 	}
 }
 
+// sizeItem is one of the two hardware entries. What greys it out comes from
+// sizeObjection asked its weaker question — not whether some particular number
+// can be set, but whether any can right now — because the number has not been
+// typed yet when the menu is drawn.
+func sizeItem(key rune, label string, r vmRow, sz sizing, k sizeKind) menuItem {
+	short, long := sizeObjection(r, sz, k, 0)
+	return menuItem{key: key, label: label, why: long, hint: short,
+		run: func(b *browser, r vmRow) { b.resize(r, k) }}
+}
+
 // menuKey drives the menu. Letters pick an item directly; the arrows and Enter
 // do the same for anyone who would rather read than remember.
 func (b *browser) menuKey(k key) {
@@ -422,6 +449,78 @@ func (b *browser) power(r vmRow, op powerOp) {
 	b.done(msg)
 }
 
+// resize changes what the machine has: the value is typed, checked, confirmed
+// and only then sent.
+//
+// The configuration is read again here rather than taken from the menu that was
+// just drawn. It is the same read, a moment later, and the moment matters: the
+// menu's grey-out only says a change of this kind is possible at all, and
+// between drawing it and answering the question somebody else may have started
+// the machine — which turns "give it 4 GB less" from a reconfigure into
+// something vSphere will not do.
+//
+// The question at the end is the plain one, not the page that asks for YES to be
+// typed. That page is for losing something: pulling the plug, reverting,
+// removing snapshots. Nothing here is lost — a number set wrongly is set back —
+// and a confirmation asked for everything is a confirmation nobody reads.
+func (b *browser) resize(r vmRow, k sizeKind) {
+	b.closeMenu()
+	if r.sess == nil {
+		b.setStatus(colErr, "no connection to "+r.vc.Name)
+		return
+	}
+
+	sz, err := sizingOf(r.sess, r.ref)
+	if err != nil {
+		b.setStatus(colErr, err.Error())
+		return
+	}
+	if err := checkSize(r, sz, k, 0); err != nil {
+		b.setStatus(colWarn, err.Error())
+		return
+	}
+
+	typed, ok := b.input(sizePrompt(r, sz, k))
+	if !ok || typed == "" {
+		b.setStatus(colDim, "nothing done")
+		return
+	}
+	want, err := parseSize(k, typed)
+	if err != nil {
+		b.setStatus(colWarn, err.Error())
+		return
+	}
+	if err := checkSize(r, sz, k, want); err != nil {
+		b.setStatus(colWarn, err.Error())
+		return
+	}
+
+	from, to := k.shown(sz.now(k)), k.shown(want)
+	if !b.ask(SF("%s on %s: %s → %s?", r.name, r.vc.Name, from, to)) {
+		b.setStatus(colDim, "nothing done")
+		return
+	}
+
+	b.working(SF("%s: %s → %s ...", r.name, from, to))
+	msg, err := runResize(r.sess, r, sz, k, want)
+	if err != nil {
+		b.setStatus(colErr, err.Error())
+		return
+	}
+	b.done(msg)
+}
+
+// sizePrompt is the label on that line. It carries the current value, so the
+// number being replaced is in front of the person replacing it, and for memory
+// the unit as well — a field that takes 16 and means gigabytes has to say so
+// where it is typed, not in a manual.
+func sizePrompt(r vmRow, sz sizing, k sizeKind) string {
+	if k == sizeCPUs {
+		return SF("vCPUs for %s (now %d): ", r.name, sz.cpus)
+	}
+	return SF("memory for %s in GB (now %s, or 512m): ", r.name, k.shown(sz.memoryMB))
+}
+
 // working puts a line on the screen before an operation that will block the loop
 // — a vCenter task can take minutes, and a terminal that goes silent for that
 // long looks like a hang.
@@ -603,7 +702,7 @@ func (b *browser) renderMenu() {
 		segLine(&sb, cols, seg{b.statusCol, b.status})
 	} else {
 		segLine(&sb, cols, seg{colDim,
-			"lowercase asks the guest, uppercase the hypervisor"})
+			"of the power pairs, lowercase asks the guest and uppercase the hypervisor"})
 	}
 	sb.WriteString(colDim + truncate("a letter or ↑/↓ and ⏎ to choose   esc back", cols) + attrOff + scrEOL)
 	b.write(sb.String())

actions_test.go

@@ -137,7 +137,7 @@ func TestMenuAvailability(t *testing.T) {
 	}
 	someSnaps := []snapEntry{{name: "s1", created: "01.01.2026 00:00"}}
 
-	running := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOn, toolsUp), someSnaps)
+	running := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOn, toolsUp), someSnaps, testSizing())
 	for _, k := range []rune{'n', 'r', 'd', 'D', 's', 'b', 'S', 'B'} {
 		if !find(running, k).available() {
 			t.Errorf("%q not offered for a running machine with Tools: %s", string(k), find(running, k).why)
@@ -147,7 +147,7 @@ func TestMenuAvailability(t *testing.T) {
 		t.Error("power on is offered for a machine that is already running")
 	}
 
-	noTools := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOn, toolsDown), someSnaps)
+	noTools := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOn, toolsDown), someSnaps, testSizing())
 	for _, k := range []rune{'s', 'b'} {
 		if find(noTools, k).available() {
 			t.Errorf("%q offered without VMware Tools", string(k))
@@ -159,7 +159,7 @@ func TestMenuAvailability(t *testing.T) {
 		}
 	}
 
-	stopped := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOff, toolsDown), someSnaps)
+	stopped := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOff, toolsDown), someSnaps, testSizing())
 	if !find(stopped, 'o').available() {
 		t.Error("power on is not offered for a stopped machine")
 	}
@@ -170,7 +170,7 @@ func TestMenuAvailability(t *testing.T) {
 	}
 
 	// Without snapshots there is nothing to revert to or remove.
-	bare := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOn, toolsUp), nil)
+	bare := b.buildMenu(stateRow(types.VirtualMachinePowerStatePoweredOn, toolsUp), nil, testSizing())
 	for _, k := range []rune{'r', 'd', 'D'} {
 		if find(bare, k).available() {
 			t.Errorf("%q offered for a machine with no snapshots", string(k))
@@ -395,7 +395,7 @@ func TestMenuHintAndReasonAgree(t *testing.T) {
 		stateRow(types.VirtualMachinePowerStatePoweredOff, toolsDown),
 		stateRow(types.VirtualMachinePowerStateSuspended, toolsUp),
 	} {
-		for _, m := range b.buildMenu(r, nil) {
+		for _, m := range b.buildMenu(r, nil, testSizing()) {
 			if m.isSeparator() {
 				continue
 			}
@@ -606,15 +606,15 @@ func TestMenuDropsItsFactsBeforeItsChoices(t *testing.T) {
 		wantFacts bool
 	}{
 		{"30", true},  // room for both, all four facts
-		{"19", true},  // room for three of them, the hostname among them
-		{"18", false}, // room for two: the state and the address
-		{"13", false}, // no room at all, so the choices have the screen
+		{"22", true},  // room for three of them, the hostname among them
+		{"21", false}, // room for two: the state and the address
+		{"16", false}, // no room at all, so the choices have the screen
 	} {
 		t.Setenv("LINES", c.rows)
 
 		r := testRow("web01", true, "10.0.0.5")
 		b := &browser{rows: []vmRow{r}, view: []int{0}}
-		b.menu = b.buildMenu(r, nil)
+		b.menu = b.buildMenu(r, nil, testSizing())
 		b.menuInfo = sheetPick(vmDetail(r, nil, ""), menuFacts)
 
 		frame := renderToPipe(t, b, b.renderMenu)
@@ -761,3 +761,11 @@ func TestEveryTaskWaitIsBounded(t *testing.T) {
 		t.Error("no task wait found at all — this check has stopped checking anything")
 	}
 }
+
+// testSizing is a plausible machine's hardware for the menu tests: four vCPUs
+// in one socket, eight gigabytes, and none of the three hot-plug settings — the
+// way most machines are actually built, and the case where the two hardware
+// entries are only offered on a machine that is switched off.
+func testSizing() sizing {
+	return sizing{cpus: 4, coresPerSocket: 1, memoryMB: 8192, known: true}
+}

browse.go

@@ -742,6 +742,7 @@ type browser struct {
 	// underneath without having to remember where it came from.
 	menu      []menuItem
 	menuSnaps []snapEntry
+	menuSize  sizing      // what the machine has, for the two hardware entries
 	menuInfo  []sheetLine // the few lines of the sheet shown above the choices
 	menuSel   int
 	pick      *picker

browse_test.go

@@ -1463,7 +1463,7 @@ func TestEveryScreenDrawsWhatItHasToSay(t *testing.T) {
 		}
 	}
 
-	b.menu = b.buildMenu(*b.current(), b.current().snaps)
+	b.menu = b.buildMenu(*b.current(), b.current().snaps, testSizing())
 	b.menuInfo = sheetPick(vmDetail(*b.current(), nil, ""), menuFacts)
 	menu := stripEscapes(renderToPipe(t, b, b.renderMenu))
 	for _, want := range []string{"take a snapshot", "power off", "reset"} {

complete.go

@@ -244,7 +244,7 @@ func inventoryAge() string {
 var (
 	vmFlags = []string{"-l", "--list", "-n", "--new", "-r", "--remove", "--revert",
 		"--removeall", "-o", "--on", "-s", "--shutdown", "-b", "--reboot",
-		"--off", "--reset"}
+		"--off", "--reset", "--vm"}
 	vcFlags = []string{"-v", "--vcenter", "-p", "--password"}
 )
 

guest_test.go

@@ -282,7 +282,7 @@ func TestTheSheetSaysWhyItCannotConnect(t *testing.T) {
 func TestMenuLettersAreDistinct(t *testing.T) {
 	b := &browser{}
 	seen := map[rune]string{}
-	for _, m := range b.buildMenu(testRow("web01", true, "10.0.0.5"), nil) {
+	for _, m := range b.buildMenu(testRow("web01", true, "10.0.0.5"), nil, testSizing()) {
 		if m.isSeparator() {
 			continue
 		}

gvm.go

@@ -131,6 +131,16 @@ func run() error {
 	subPower.String(&pwOff, "", "off", "Power off <vm> at the hypervisor — hard, like pulling the plug")
 	subPower.String(&pwReset, "", "reset", "Reset <vm> at the hypervisor — hard, like the reset button")
 
+	// The machine is a flag of its own here, not the value of the action flag as
+	// it is for power and snap: this command takes a machine *and* a number, and
+	// only one of the two can be the value of "--cpus".
+	var sizeVM, sizeCPUs, sizeMemory string
+	subSize := flaggy.NewSubcommand("size")
+	subSize.Description = "Show or change a machine's vCPUs and memory"
+	subSize.String(&sizeVM, "", "vm", "The machine to show or change")
+	subSize.String(&sizeCPUs, "c", "cpus", "Set its vCPU count")
+	subSize.String(&sizeMemory, "m", "memory", "Set its memory, in GB (or 512m for MB)")
+
 	var hostCount, hostTelemetry bool
 	subHost := flaggy.NewSubcommand("host")
 	subHost.Description = "Host commands"
@@ -158,6 +168,7 @@ func run() error {
 	flaggy.AttachSubcommand(subVM, 1)
 	flaggy.AttachSubcommand(subSnap, 1)
 	flaggy.AttachSubcommand(subPower, 1)
+	flaggy.AttachSubcommand(subSize, 1)
 	flaggy.AttachSubcommand(subHost, 1)
 	flaggy.AttachSubcommand(subDS, 1)
 	flaggy.AttachSubcommand(subLog, 1)
@@ -265,6 +276,16 @@ func run() error {
 			return errf("one power operation at a time, not %d", len(given))
 		}
 
+	case subSize.Used:
+		vc, err := cfg.pick(vcname)
+		if err != nil {
+			return err
+		}
+		if sizeVM == "" {
+			return errf("size needs a machine: gvm size --vm <machine> [-c <vcpus>] [-m <memory>]")
+		}
+		return sizeCLI(vc, sizeVM, sizeCPUs, sizeMemory, yes)
+
 	case subHost.Used:
 		vc, err := cfg.pick(vcname)
 		if err != nil {

resize.go

@@ -0,0 +1,438 @@
+// resize.go — changing what a machine has: vCPUs and memory.
+//
+// This is the third kind of thing gvm does to a machine, after its power and
+// its snapshots, and it is the one with the most ways to be refused. vSphere
+// will not take just any number:
+//
+//  1. A running machine can only grow, and only where it was built to. CPU and
+//     memory hot-add are per-machine settings somebody turned on when the
+//     machine was made; without them the machine has to be powered off first.
+//     Memory can never shrink while it runs — there is no hot-remove for it at
+//     all — and vCPUs only where hot-remove is on as well.
+//  2. The vCPU count has to be a multiple of the cores per socket. gvm does not
+//     quietly change the socket topology to make a number fit: software is
+//     licensed per socket, and a tool that turns 2 sockets into 4 to satisfy an
+//     odd vCPU count would be writing somebody an invoice.
+//  3. Memory is a whole number of megabytes, in multiples of four.
+//
+// All of that is asked before anything is sent, in the same shape the power
+// operations use: an objection in two lengths, one short enough for the menu's
+// own column and one to be read on its own, both out of one function so the
+// menu and the message cannot disagree.
+package main
+
+import (
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/vmware/govmomi/object"
+	"github.com/vmware/govmomi/units"
+	"github.com/vmware/govmomi/vim25/mo"
+	"github.com/vmware/govmomi/vim25/types"
+)
+
+// reconfigWait is how long gvm watches a reconfigure before it stops watching.
+// The task itself is usually over in a second — the machine is not copied or
+// moved, only its configuration is written — so this is a limit on a frozen
+// terminal, not on the operation. Like every other wait here, vCenter carries
+// on regardless.
+const reconfigWait = 5 * time.Minute
+
+// sizeKind is which of the two is being changed. They are separate operations
+// with separate rules, not two fields of one: memory can never shrink while a
+// machine runs and vCPUs sometimes can, and a menu entry that greys out for
+// both reasons at once could not say why.
+type sizeKind int
+
+const (
+	sizeCPUs sizeKind = iota
+	sizeMemory
+)
+
+func (k sizeKind) what() string {
+	if k == sizeCPUs {
+		return "vCPU count"
+	}
+	return "memory"
+}
+
+// sizing is what a machine has and what may be changed while it runs. It comes
+// from `config`, which the inventory sweep deliberately does not read — it is
+// the whole configuration of a machine, and this wants four fields of it — so
+// it is asked for one machine at a time, when somebody is about to change it.
+type sizing struct {
+	cpus           int32
+	coresPerSocket int32
+	memoryMB       int32
+	cpuHotAdd      bool
+	cpuHotRemove   bool
+	memoryHotAdd   bool
+	known          bool // false when the configuration could not be read at all
+}
+
+// sizingProps are those four fields and the two figures they are about. Named
+// paths rather than "config": the whole configuration of a machine is a large
+// document, and this is a menu being drawn.
+var sizingProps = []string{
+	"config.hardware.numCPU",
+	"config.hardware.numCoresPerSocket",
+	"config.hardware.memoryMB",
+	"config.cpuHotAddEnabled",
+	"config.cpuHotRemoveEnabled",
+	"config.memoryHotAddEnabled",
+}
+
+// sizingOf reads them. A machine whose configuration cannot be read is not a
+// failure to report on its own: the caller gets a sizing that says it knows
+// nothing, no objection is raised from here, and vCenter is left to refuse what
+// it will not take. Better a server's own error than a guess dressed as one.
+func sizingOf(s *session, ref types.ManagedObjectReference) (sizing, error) {
+	if s == nil {
+		return sizing{}, errf("no connection to read the configuration over")
+	}
+	var mvm mo.VirtualMachine
+	vm := object.NewVirtualMachine(s.client.Client, ref)
+	if err := vm.Properties(s.ctx, ref, sizingProps, &mvm); err != nil {
+		return sizing{}, errf("%s: cannot read the configuration of %s: %w",
+			s.vc.Name, vmName(s, ref), err)
+	}
+	return sizingFrom(mvm.Config), nil
+}
+
+// sizingFrom is the same from the property itself, so the rules below can be
+// exercised without a server.
+func sizingFrom(cfg *types.VirtualMachineConfigInfo) sizing {
+	if cfg == nil {
+		return sizing{}
+	}
+	sz := sizing{
+		cpus:     cfg.Hardware.NumCPU,
+		memoryMB: cfg.Hardware.MemoryMB,
+		known:    true,
+	}
+	// The cores per socket and the three flags are pointers: unset means the
+	// machine predates the setting or vCenter did not send it. Unset is one
+	// core per socket, which divides into everything, and off.
+	sz.coresPerSocket = 1
+	if cfg.Hardware.NumCoresPerSocket != nil {
+		sz.coresPerSocket = *cfg.Hardware.NumCoresPerSocket
+	}
+	if cfg.CpuHotAddEnabled != nil {
+		sz.cpuHotAdd = *cfg.CpuHotAddEnabled
+	}
+	if cfg.CpuHotRemoveEnabled != nil {
+		sz.cpuHotRemove = *cfg.CpuHotRemoveEnabled
+	}
+	if cfg.MemoryHotAddEnabled != nil {
+		sz.memoryHotAdd = *cfg.MemoryHotAddEnabled
+	}
+	return sz
+}
+
+// now is the current value of whichever of the two this is, and shown is it in
+// the words the sheet uses — "4 vCPU", "8.0GB" — so a message about a change
+// and the line above it read as the same figure.
+func (sz sizing) now(k sizeKind) int32 {
+	if k == sizeCPUs {
+		return sz.cpus
+	}
+	return sz.memoryMB
+}
+
+func (k sizeKind) shown(v int32) string {
+	if k == sizeCPUs {
+		return SF("%d vCPU", v)
+	}
+	return units.ByteSize(int64(v) * 1024 * 1024).String()
+}
+
+// ------------------------------------------------------------- what was typed
+
+// parseSize turns what somebody typed into the number vSphere wants: a vCPU
+// count, or a memory size in megabytes.
+//
+// Memory is read as gigabytes, because that is the unit the sheet shows and the
+// unit anybody says out loud — "give it 16" is never sixteen megabytes. An
+// explicit unit overrides that, so 512m is still sayable, and a fraction is
+// taken where it lands on a whole megabyte: 1.5g is 1536 MB.
+func parseSize(k sizeKind, text string) (int32, error) {
+	t := strings.ToLower(strings.TrimSpace(text))
+	if t == "" {
+		return 0, errf("nothing typed")
+	}
+	if k == sizeCPUs {
+		n, err := strconv.Atoi(t)
+		if err != nil {
+			return 0, errf("%q is not a number of vCPUs", text)
+		}
+		if n < 1 {
+			return 0, errf("a machine has at least one vCPU, not %d", n)
+		}
+		if n > maxCPUs {
+			return 0, errf("%d vCPUs is past anything vSphere builds — a typo?", n)
+		}
+		return int32(n), nil
+	}
+
+	unit := "g"
+	for _, suffix := range []string{"mb", "gb", "m", "g"} {
+		if strings.HasSuffix(t, suffix) {
+			unit, t = suffix[:1], strings.TrimSpace(strings.TrimSuffix(t, suffix))
+			break
+		}
+	}
+	v, err := strconv.ParseFloat(t, 64)
+	if err != nil {
+		return 0, errf("%q is not an amount of memory", text)
+	}
+	mb := v
+	if unit == "g" {
+		mb = v * 1024
+	}
+	if mb < 4 {
+		return 0, errf("%s is less memory than a machine can have", text)
+	}
+	if mb > maxMemoryMB {
+		return 0, errf("%s is more memory than vSphere takes — a typo?", text)
+	}
+	if mb != float64(int64(mb)) {
+		return 0, errf("%s is not a whole number of megabytes", text)
+	}
+	return int32(mb), nil
+}
+
+// The two ceilings are not vSphere's exact maxima, which move with every
+// release and with the hardware version of the machine. They are there to catch
+// a finger that stayed on a key: past these, a number is a typo rather than an
+// intention, and everything below them is left to the server to accept or
+// refuse with its own reasons.
+const (
+	maxCPUs     = 1024
+	maxMemoryMB = 32 * 1024 * 1024 // 32 TB
+)
+
+// -------------------------------------------------------------- the objection
+
+// sizeObjection says why this machine cannot be given that, in two lengths, the
+// same as powerObjection. Both the menu and the message come from here.
+//
+// A want of 0 asks the weaker question the menu asks while it is being drawn:
+// not "can it have six" but "is there any number at all it could be given right
+// now" — which is what decides whether the entry is offered or greyed out.
+func sizeObjection(r vmRow, sz sizing, k sizeKind, want int32) (short, long string) {
+	// Nothing is claimed about a machine whose configuration could not be read.
+	// vCenter is the authority on what it will take, and it says so itself.
+	if !sz.known {
+		return "", ""
+	}
+	running := r.running()
+
+	if want == 0 {
+		switch {
+		case !running:
+			return "", ""
+		case k == sizeCPUs && !sz.cpuHotAdd && !sz.cpuHotRemove:
+			return "needs it off", SF("%s is running and has neither CPU hot-add nor hot-remove — "+
+				"power it off to change the vCPU count", r.name)
+		case k == sizeMemory && !sz.memoryHotAdd:
+			return "needs it off", SF("%s is running and has no memory hot-add — "+
+				"power it off to change its memory", r.name)
+		}
+		return "", ""
+	}
+
+	now := sz.now(k)
+	if want == now {
+		return "unchanged", SF("%s already has %s", r.name, k.shown(now))
+	}
+
+	if k == sizeCPUs {
+		// The socket topology is the machine's, not gvm's to adjust: a vCPU
+		// count that does not divide into it is refused with the two counts
+		// that do, rather than made to fit by changing the number of sockets.
+		if per := sz.coresPerSocket; per > 1 && want%per != 0 {
+			below, above := want-want%per, want-want%per+per
+			return "not a whole socket", SF("%s has %d cores per socket, so its vCPUs come in "+
+				"multiples of %d — %d or %d, not %d", r.name, per, per, below, above, want)
+		}
+		switch {
+		case running && want > now && !sz.cpuHotAdd:
+			return "no CPU hot-add", SF("%s is running and CPU hot-add is off — "+
+				"power it off to give it more than %d vCPU", r.name, now)
+		case running && want < now && !sz.cpuHotRemove:
+			return "no CPU hot-remove", SF("%s is running and CPU hot-remove is off — "+
+				"power it off to take vCPUs away from it", r.name)
+		}
+		return "", ""
+	}
+
+	switch {
+	case want%4 != 0:
+		return "not a multiple of 4 MB", SF("memory is set in multiples of 4 MB, and %d MB is not one", want)
+	case running && want < now:
+		// Not a flag anybody can turn on: vSphere has no memory hot-remove.
+		return "cannot shrink while on", SF("%s is running, and memory can never be taken away from "+
+			"a running machine — power it off first", r.name)
+	case running && !sz.memoryHotAdd:
+		return "no memory hot-add", SF("%s is running and memory hot-add is off — "+
+			"power it off to change its memory", r.name)
+	}
+	return "", ""
+}
+
+// checkSize is that objection as an error, or nil. Asked before the change is
+// offered and again immediately before it is sent: between a menu being drawn
+// and a confirmation being answered, somebody else may have powered the machine
+// on.
+func checkSize(r vmRow, sz sizing, k sizeKind, want int32) error {
+	if _, long := sizeObjection(r, sz, k, want); long != "" {
+		return errf("%s", long)
+	}
+	return nil
+}
+
+// hotly reports whether this change is going to happen underneath a running
+// guest, which is worth saying afterwards: an operating system does not
+// necessarily notice on its own that it has been given another four processors.
+func hotly(r vmRow, k sizeKind, sz sizing, want int32) bool {
+	return r.running() && want > sz.now(k)
+}
+
+// ------------------------------------------------------------------ doing it
+
+// runResize sends the change and waits for it. One task per call even when both
+// numbers move, because the two are separate operations everywhere else in gvm
+// and a single message that half worked would be the worst of both.
+func runResize(s *session, r vmRow, sz sizing, k sizeKind, want int32) (message string, err error) {
+	if err := checkSize(r, sz, k, want); err != nil {
+		return "", err
+	}
+
+	spec := types.VirtualMachineConfigSpec{}
+	if k == sizeCPUs {
+		spec.NumCPUs = want
+	} else {
+		spec.MemoryMB = int64(want)
+	}
+
+	vm := object.NewVirtualMachine(s.client.Client, r.ref)
+	task, err := vm.Reconfigure(s.ctx, spec)
+	if err != nil {
+		return "", errf("%s: cannot change the %s of %s: %w", s.vc.Name, k.what(), r.name, err)
+	}
+	what := SF("%s of %s", k.what(), r.name)
+	if err := waitTask(s.ctx, task, reconfigWait, what); err != nil {
+		return "", err
+	}
+
+	msg := SF("%s: %s → %s", r.name, k.shown(sz.now(k)), k.shown(want))
+	if hotly(r, k, sz, want) {
+		msg += " — added while it runs; the guest may have to bring it online"
+	}
+	return msg, nil
+}
+
+// ---------------------------------------------------------- the command line
+
+// sizeCLI is `gvm size`: with no number it says what the machine has, and with
+// one it changes it. The two live in one command because "what has it got" is
+// the question one asks immediately before "give it more", and having to
+// remember two spellings of the same noun to ask both is a small tax.
+func sizeCLI(vc VCenter, vmname, cpus, memory string, yes bool) error {
+	s, err := connect(vc)
+	if err != nil {
+		return err
+	}
+	defer s.close()
+
+	vm, err := s.vm(vmname)
+	if err != nil {
+		return err
+	}
+
+	// Read as fresh as the operation is going to be: what is offered and what is
+	// refused both depend on whether the machine is running right now.
+	var mvm mo.VirtualMachine
+	if err := vm.Properties(s.ctx, vm.Reference(), append([]string{"summary", "guest"}, sizingProps...), &mvm); err != nil {
+		return errf("%s: cannot read %s: %w", vc.Name, vm.Name(), err)
+	}
+	r := vmRow{vc: vc, sess: s, ref: vm.Reference(), name: vm.Name(), vm: mvm}
+	sz := sizingFrom(mvm.Config)
+
+	if cpus == "" && memory == "" {
+		sizeShow(r, sz)
+		return nil
+	}
+
+	for _, c := range []struct {
+		kind sizeKind
+		text string
+	}{{sizeCPUs, cpus}, {sizeMemory, memory}} {
+		if c.text == "" {
+			continue
+		}
+		want, err := parseSize(c.kind, c.text)
+		if err != nil {
+			return err
+		}
+		if err := checkSize(r, sz, c.kind, want); err != nil {
+			return err
+		}
+
+		ok, err := confirm(SF("%s on %s: %s → %s?", r.name, vc.Name,
+			c.kind.shown(sz.now(c.kind)), c.kind.shown(want)), yes)
+		if err != nil || !ok {
+			return err
+		}
+
+		msg, err := runResize(s, r, sz, c.kind, want)
+		if err != nil {
+			return err
+		}
+		PO(msg)
+
+		// The second change is checked against what the first one left behind,
+		// not against what was read before either of them.
+		if c.kind == sizeCPUs {
+			sz.cpus = want
+		} else {
+			sz.memoryMB = want
+		}
+	}
+	return nil
+}
+
+// sizeShow prints what the machine has and what could be changed without
+// stopping it — the second being the thing one actually wants to know before
+// planning the work, and the thing no listing anywhere else says.
+func sizeShow(r vmRow, sz sizing) {
+	if !sz.known {
+		PE("the configuration of " + r.name + " could not be read")
+		return
+	}
+	PF("%-14s %s\n", "machine", r.name+"  ("+r.powerLong()+")")
+	PF("%-14s %s\n", "vCPU", SF("%d, in %d per socket", sz.cpus, sz.coresPerSocket))
+	PF("%-14s %s\n", "memory", sizeMemory.shown(sz.memoryMB))
+	PF("%-14s %s\n", "while it runs", liveChanges(sz))
+}
+
+// liveChanges is that last line: which of the three hot-plug settings this
+// machine was built with, said as what they let one do rather than as the names
+// of the flags.
+func liveChanges(sz sizing) string {
+	var can []string
+	if sz.cpuHotAdd {
+		can = append(can, "add vCPUs")
+	}
+	if sz.cpuHotRemove {
+		can = append(can, "remove vCPUs")
+	}
+	if sz.memoryHotAdd {
+		can = append(can, "add memory")
+	}
+	if len(can) == 0 {
+		return "nothing — it has to be powered off to be changed"
+	}
+	return strings.Join(can, ", ")
+}

resize_test.go

@@ -0,0 +1,254 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/vmware/govmomi/vim25/mo"
+	"github.com/vmware/govmomi/vim25/types"
+)
+
+// sizedRow is a machine in a given power state, for the rules below. Only the
+// power state is read off it: everything else a resize depends on comes from
+// the sizing, which is read separately from the machine's configuration.
+func sizedRow(state types.VirtualMachinePowerState) vmRow {
+	return vmRow{
+		name: "web01",
+		vc:   VCenter{Name: "v308"},
+		vm: mo.VirtualMachine{Summary: types.VirtualMachineSummary{
+			Runtime: types.VirtualMachineRuntimeInfo{PowerState: state},
+		}},
+	}
+}
+
+// What somebody types has to become the number vSphere wants, or a refusal that
+// says which part of it was not a number.
+func TestParseSize(t *testing.T) {
+	for _, c := range []struct {
+		kind sizeKind
+		text string
+		want int32
+		bad  string // a piece of the error, when it is meant to be refused
+	}{
+		{kind: sizeCPUs, text: "4", want: 4},
+		{kind: sizeCPUs, text: " 16 ", want: 16},
+		{kind: sizeCPUs, text: "0", bad: "at least one"},
+		{kind: sizeCPUs, text: "-2", bad: "at least one"},
+		{kind: sizeCPUs, text: "4.5", bad: "not a number"},
+		{kind: sizeCPUs, text: "eight", bad: "not a number"},
+		{kind: sizeCPUs, text: "99999", bad: "typo"},
+
+		// Memory is gigabytes unless it says otherwise: nobody means 16 MB.
+		{kind: sizeMemory, text: "16", want: 16384},
+		{kind: sizeMemory, text: "8g", want: 8192},
+		{kind: sizeMemory, text: "8GB", want: 8192},
+		{kind: sizeMemory, text: "512m", want: 512},
+		{kind: sizeMemory, text: "512mb", want: 512},
+		{kind: sizeMemory, text: "1.5g", want: 1536},
+		{kind: sizeMemory, text: "0", bad: "less memory"},
+		{kind: sizeMemory, text: "0.0001g", bad: "less memory"},
+		{kind: sizeMemory, text: "4.5m", bad: "whole number"},
+		{kind: sizeMemory, text: "lots", bad: "not an amount"},
+		{kind: sizeMemory, text: "99999g", bad: "typo"},
+	} {
+		got, err := parseSize(c.kind, c.text)
+		switch {
+		case c.bad != "":
+			if err == nil {
+				t.Errorf("parseSize(%q) = %d, want a refusal", c.text, got)
+			} else if !strings.Contains(err.Error(), c.bad) {
+				t.Errorf("parseSize(%q) refused with %q, which does not mention %q", c.text, err, c.bad)
+			}
+		case err != nil:
+			t.Errorf("parseSize(%q): %v", c.text, err)
+		case got != c.want:
+			t.Errorf("parseSize(%q) = %d, want %d", c.text, got, c.want)
+		}
+	}
+}
+
+// The rules a running machine is held to. This is the heart of the feature: what
+// vSphere will refuse has to be refused here first, with the reason, rather than
+// sent and bounced with a stack of SOAP.
+func TestSizeObjectionOnARunningMachine(t *testing.T) {
+	on := sizedRow(types.VirtualMachinePowerStatePoweredOn)
+	off := sizedRow(types.VirtualMachinePowerStatePoweredOff)
+
+	plain := sizing{cpus: 4, coresPerSocket: 1, memoryMB: 8192, known: true}
+	hot := sizing{cpus: 4, coresPerSocket: 1, memoryMB: 8192, known: true,
+		cpuHotAdd: true, cpuHotRemove: true, memoryHotAdd: true}
+
+	for _, c := range []struct {
+		what string
+		row  vmRow
+		sz   sizing
+		kind sizeKind
+		want int32
+		bad  string // a piece of the objection, or "" when it must be allowed
+	}{
+		// Powered off, anything goes.
+		{"more vCPUs, machine off", off, plain, sizeCPUs, 8, ""},
+		{"fewer vCPUs, machine off", off, plain, sizeCPUs, 2, ""},
+		{"more memory, machine off", off, plain, sizeMemory, 16384, ""},
+		{"less memory, machine off", off, plain, sizeMemory, 4096, ""},
+
+		// Running, without the settings that would allow it.
+		{"more vCPUs, no hot-add", on, plain, sizeCPUs, 8, "hot-add is off"},
+		{"fewer vCPUs, no hot-remove", on, plain, sizeCPUs, 2, "hot-remove is off"},
+		{"more memory, no hot-add", on, plain, sizeMemory, 16384, "hot-add is off"},
+
+		// Running, with them.
+		{"more vCPUs, hot-add on", on, hot, sizeCPUs, 8, ""},
+		{"fewer vCPUs, hot-remove on", on, hot, sizeCPUs, 2, ""},
+		{"more memory, hot-add on", on, hot, sizeMemory, 16384, ""},
+
+		// The one no setting can allow: vSphere has no memory hot-remove.
+		{"less memory, hot-add on", on, hot, sizeMemory, 4096, "never be taken away"},
+
+		// Nothing to do.
+		{"the same vCPUs", on, hot, sizeCPUs, 4, "already"},
+		{"the same memory", on, hot, sizeMemory, 8192, "already"},
+
+		// Memory is whole multiples of four megabytes.
+		{"memory of 10 MB", off, plain, sizeMemory, 10, "multiples of 4 MB"},
+
+		// A configuration that could not be read claims nothing: the server is
+		// left to accept or refuse with its own reasons.
+		{"unknown configuration", on, sizing{}, sizeCPUs, 64, ""},
+	} {
+		short, long := sizeObjection(c.row, c.sz, c.kind, c.want)
+		switch {
+		case c.bad == "":
+			if long != "" {
+				t.Errorf("%s: refused with %q", c.what, long)
+			}
+		case long == "":
+			t.Errorf("%s: allowed, want a refusal mentioning %q", c.what, c.bad)
+		case !strings.Contains(long, c.bad):
+			t.Errorf("%s: refused with %q, which does not mention %q", c.what, long, c.bad)
+		}
+		// Both lengths or neither: the menu column and the message come from
+		// here together, and one without the other greys an entry out with
+		// nothing to explain it.
+		if (short == "") != (long == "") {
+			t.Errorf("%s: short %q and long %q disagree about whether there is an objection",
+				c.what, short, long)
+		}
+	}
+}
+
+// The socket topology is the machine's own. A vCPU count that does not divide
+// into it is refused with the two that do, rather than made to fit by changing
+// the number of sockets underneath somebody's per-socket licence.
+func TestSizeKeepsTheSocketTopology(t *testing.T) {
+	off := sizedRow(types.VirtualMachinePowerStatePoweredOff)
+	sz := sizing{cpus: 8, coresPerSocket: 4, memoryMB: 8192, known: true}
+
+	_, long := sizeObjection(off, sz, sizeCPUs, 6)
+	if long == "" {
+		t.Fatal("6 vCPUs was allowed on a machine with 4 cores per socket")
+	}
+	for _, want := range []string{"4 cores per socket", "4 or 8"} {
+		if !strings.Contains(long, want) {
+			t.Errorf("the refusal does not say %q: %q", want, long)
+		}
+	}
+	if _, long := sizeObjection(off, sz, sizeCPUs, 12); long != "" {
+		t.Errorf("12 vCPUs is three whole sockets and was refused: %q", long)
+	}
+}
+
+// A machine whose configuration says nothing about the hot-plug settings is a
+// machine without them, and one core per socket divides into everything — the
+// fields are pointers, and unset must not read as zero cores per socket.
+func TestSizingFromAnEmptyConfiguration(t *testing.T) {
+	if sz := sizingFrom(nil); sz.known {
+		t.Error("a machine with no configuration claimed to know its sizing")
+	}
+
+	sz := sizingFrom(&types.VirtualMachineConfigInfo{
+		Hardware: types.VirtualHardware{NumCPU: 4, MemoryMB: 8192},
+	})
+	if !sz.known {
+		t.Fatal("a configuration that was read is said to be unknown")
+	}
+	if sz.coresPerSocket != 1 {
+		t.Errorf("cores per socket = %d, want 1 where the server did not say", sz.coresPerSocket)
+	}
+	if sz.cpuHotAdd || sz.cpuHotRemove || sz.memoryHotAdd {
+		t.Error("a setting the server did not send was taken for on")
+	}
+
+	yes := true
+	four := int32(4)
+	sz = sizingFrom(&types.VirtualMachineConfigInfo{
+		Hardware:            types.VirtualHardware{NumCPU: 8, MemoryMB: 16384, NumCoresPerSocket: &four},
+		CpuHotAddEnabled:    &yes,
+		MemoryHotAddEnabled: &yes,
+	})
+	if sz.coresPerSocket != 4 || !sz.cpuHotAdd || !sz.memoryHotAdd || sz.cpuHotRemove {
+		t.Errorf("the settings did not come through: %+v", sz)
+	}
+}
+
+// The two entries are greyed out with the reason on a machine that cannot take
+// the change at all, and offered on one that can — which is the weaker question
+// the menu asks, before any number has been typed.
+func TestTheMenuOffersTheHardwareEntries(t *testing.T) {
+	b := &browser{}
+	find := func(items []menuItem, k rune) menuItem {
+		t.Helper()
+		for _, m := range items {
+			if m.key == k {
+				return m
+			}
+		}
+		t.Fatalf("no menu entry %q", string(k))
+		return menuItem{}
+	}
+
+	plain := sizing{cpus: 4, coresPerSocket: 1, memoryMB: 8192, known: true}
+	hot := plain
+	hot.cpuHotAdd, hot.memoryHotAdd = true, true
+
+	running := b.buildMenu(sizedRow(types.VirtualMachinePowerStatePoweredOn), nil, plain)
+	for _, k := range []rune{'c', 'm'} {
+		m := find(running, k)
+		if m.available() {
+			t.Errorf("%q is offered on a running machine with no hot-plug", string(k))
+		}
+		if m.hint == "" || m.why == "" {
+			t.Errorf("%q is greyed out without saying why", string(k))
+		}
+	}
+
+	for _, c := range []struct {
+		what string
+		menu []menuItem
+	}{
+		{"a machine that is off", b.buildMenu(sizedRow(types.VirtualMachinePowerStatePoweredOff), nil, plain)},
+		{"a running machine with hot-add", b.buildMenu(sizedRow(types.VirtualMachinePowerStatePoweredOn), nil, hot)},
+	} {
+		for _, k := range []rune{'c', 'm'} {
+			if m := find(c.menu, k); !m.available() {
+				t.Errorf("%q is not offered on %s: %s", string(k), c.what, m.why)
+			}
+		}
+	}
+}
+
+// What the messages call the two figures is what the sheet calls them, so a
+// change and the line it changes read as the same number.
+func TestSizeIsShownTheWayTheSheetShowsIt(t *testing.T) {
+	if got := sizeCPUs.shown(4); got != "4 vCPU" {
+		t.Errorf("vCPUs shown as %q", got)
+	}
+	if got := sizeMemory.shown(8192); got != "8.0GB" {
+		t.Errorf("memory shown as %q, want the sheet's own spelling", got)
+	}
+	r := vmRow{vm: mo.VirtualMachine{Summary: types.VirtualMachineSummary{
+		Config: types.VirtualMachineConfigSummary{MemorySizeMB: 8192}}}}
+	if sheet, msg := r.memory(), sizeMemory.shown(8192); sheet != msg {
+		t.Errorf("the sheet says %q and a resize says %q", sheet, msg)
+	}
+}

sim_test.go

@@ -1218,6 +1218,88 @@ func TestSimEventsWithoutAConnection(t *testing.T) {
 	}
 }
 
+// Changing what a machine has, against a server that answers: the refusal on a
+// running machine, and the change itself once it is off. The numbers are read
+// back from the vCenter afterwards rather than assumed — a reconfigure that is
+// accepted and does nothing would otherwise look exactly like one that worked.
+func TestSimResizeAMachine(t *testing.T) {
+	quiet(t)
+	vc := simVCenter(t)
+
+	s, r := oneRow(t, vc, "DC0_C0_RP0_VM0")
+	sz, err := sizingOf(s, r.ref)
+	if err != nil {
+		t.Fatalf("sizingOf: %v", err)
+	}
+	if !sz.known {
+		t.Fatal("the machine's configuration came back empty")
+	}
+
+	// The simulator's machines run, and are built without hot-plug — which is
+	// the case the objection exists for.
+	if !r.running() {
+		t.Fatal("the simulated machine is not running, so there is nothing to refuse")
+	}
+	if err := checkSize(r, sz, sizeCPUs, sz.cpus+2); err == nil {
+		t.Error("more vCPUs were allowed on a running machine with no hot-add")
+	}
+	if err := checkSize(r, sz, sizeMemory, sz.memoryMB*2); err == nil {
+		t.Error("more memory was allowed on a running machine with no hot-add")
+	}
+
+	// Off it goes, and with it the objection.
+	if _, err := runPower(s, r, opPowerOff); err != nil {
+		t.Fatalf("cannot power the machine off: %v", err)
+	}
+	if err := refreshOne(s, &r); err != nil {
+		t.Fatalf("cannot re-read the machine: %v", err)
+	}
+
+	wantCPUs, wantMemory := sz.cpus+2, sz.memoryMB+1024
+	for _, c := range []struct {
+		kind sizeKind
+		want int32
+	}{{sizeCPUs, wantCPUs}, {sizeMemory, wantMemory}} {
+		msg, err := runResize(s, r, sz, c.kind, c.want)
+		if err != nil {
+			t.Fatalf("runResize(%v): %v", c.kind.what(), err)
+		}
+		if !strings.Contains(msg, "→") {
+			t.Errorf("the message does not say what changed: %q", msg)
+		}
+	}
+
+	after, err := sizingOf(s, r.ref)
+	if err != nil {
+		t.Fatalf("sizingOf after the change: %v", err)
+	}
+	if after.cpus != wantCPUs {
+		t.Errorf("the machine has %d vCPUs, want %d", after.cpus, wantCPUs)
+	}
+	if after.memoryMB != wantMemory {
+		t.Errorf("the machine has %d MB, want %d", after.memoryMB, wantMemory)
+	}
+
+	// And the change that would take memory away from it while it runs is still
+	// refused after it has been given some.
+	r.vm.Summary.Runtime.PowerState = types.VirtualMachinePowerStatePoweredOn
+	if err := checkSize(r, after, sizeMemory, after.memoryMB-1024); err == nil {
+		t.Error("memory was taken away from a running machine")
+	}
+}
+
+// refreshOne re-reads the properties the sweep reads, for a row a test has just
+// changed something about.
+func refreshOne(s *session, r *vmRow) error {
+	var fresh mo.VirtualMachine
+	vm := object.NewVirtualMachine(s.client.Client, r.ref)
+	if err := vm.Properties(s.ctx, r.ref, sweepProps, &fresh); err != nil {
+		return err
+	}
+	r.vm = fresh
+	return nil
+}
+
 // The instance UUID is what the vSphere client's links are made of, and the one
 // thing gvm cannot work out from the configuration.
 func TestSimVsphereLinkFromASession(t *testing.T) {

version.txt

@@ -1 +1 @@
-1.1.7
+1.1.8