cli: a listing command refuses a name it cannot answer about (#97)

Measured on the built binary: "tfg formats png svg" described png, said
nothing at all about svg and ended with zero, and "tfg preset list some-name"
printed the whole list and ignored the name though that operation takes no
name at all. Both are silence about an argument somebody typed, and in a
script a confident answer about the wrong thing is worse than a refusal.

The second one is not in the observation that asked for this. It came out of
measuring the first, and fixing only the named half would have left that
observation's own sentence true about a different pair of commands.

Both now end with 2 and name the word they could not use. The guard asks four
commands at once, including the two that already refused, and requires the
refusal to name the rejected word - an exit code alone is satisfied by a build
that refuses everything, so the other half checks these commands still answer.

The flag spelling guard stops naming its directories by hand and derives them
from the layer map. internal/damage arrived on layer 2, under both surfaces,
without joining that list, and the hole would have taken every later package
too. The layer map is the right source because the layering guard already
refuses a package that is neither on the ladder nor declared test only, and
because it leaves out internal/oracle on purpose - that one carries real
command lines for inkscape and ffprobe in raw strings. 113 files scanned
became 128, with zero findings.

Refusing the extra name pushed internal/cli/preset.go past the file ceiling,
so it is split by what the parts do: presetcmd.go answers somebody who typed
tfg preset, preset.go turns a named question into targets. The ratchet then
took the ceiling down, 433 to 408 and crowdedFiles 1 to 0.

Three new mutations, and four existing ones retargeted after the split - only
staleness.py said they had gone stale. All eight run and caught.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: donislawdev

CHANGELOG.md

@@ -306,6 +306,25 @@ because it turns other people's test suites red.
 
 ### Changed
 
+- **Two commands now refuse a name they cannot answer about, instead of
+  quietly answering about a different one.**
+
+  ```
+  tfg formats png svg          described png and said nothing about svg, ending with 0
+  tfg preset list some-name    printed the whole list and ignored the name, ending with 0
+  ```
+
+  Both now end with 2 and name the word they could not use. A script that
+  asked about the wrong thing was getting a confident answer about something
+  else, which is worse than being told no.
+
+  `tfg preset list` takes no name at all, so anything after it was always a
+  mistake - most likely somebody reaching for `tfg preset show`.
+  The refusal says so.
+
+  Nothing changes when you pass the right number of names, and no generated
+  file moves a byte.
+
 - **A spreadsheet can now be built wider than a spreadsheet can open.** The
   `columns` setting of `xlsx` used to stop at 64. It now reaches 32768, which is
   the ceiling `csv` already had.

internal/cli/formats.go

@@ -172,9 +172,13 @@ Flags:
 	if err := fs.Parse(rest); err != nil {
 		return ExitUsage
 	}
-	wanted := leading
-	if wanted == "" && fs.NArg() == 1 {
-		wanted = fs.Arg(0)
+	// Two names used to describe the first and say nothing about the second,
+	// ending with zero: measured 2026-09-09, "tfg formats png svg" printed the
+	// card for png and ignored svg, so a script asking about the wrong thing
+	// got a confident answer about something else. O196.
+	wanted, ok := atMostOneName(leading, fs, errOut)
+	if !ok {
+		return ExitUsage
 	}
 
 	if wanted != "" {

internal/cli/preset.go

@@ -9,7 +9,6 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/donislawdev/TestingFilesGenerator/internal/core"
 	"github.com/donislawdev/TestingFilesGenerator/internal/engine"
 	"github.com/donislawdev/TestingFilesGenerator/internal/format"
 	"github.com/donislawdev/TestingFilesGenerator/internal/manifest"
@@ -338,251 +337,3 @@ func targetsFromPreset(fs *flag.FlagSet, g *generateOpts, given map[string]bool,
 	opt.Preset = record(expanded)
 	return targetsFromParsedRecipe(rec, hash, g, given, opt), ExitOK
 }
-
-func presetCmd(ctx context.Context, args []string, out, errOut io.Writer) int {
-	if len(args) > 0 {
-		switch args[0] {
-		case "list":
-			return presetList(args[1:], out, errOut)
-		case "show":
-			return presetShow(ctx, args[1:], out, errOut)
-		case "eject":
-			return presetEject(args[1:], out, errOut)
-		}
-	}
-
-	// Asking about the command itself, before any operation is named.
-	if helpRequested(args) {
-		presetUsage(out)
-		return ExitOK
-	}
-	if len(args) == 0 {
-		fmt.Fprintln(errOut, "tfg: preset takes one operation: list, show or eject. Example: tfg preset list")
-	} else {
-		fmt.Fprintf(errOut, "tfg: preset has no operation called %q. It takes list, show or eject.\n", args[0])
-	}
-	presetUsage(errOut)
-	return ExitUsage
-}
-
-func presetUsage(w io.Writer) {
-	fmt.Fprint(w, `tfg preset - build a set of files from a named test question.
-
-Usage:
-  tfg preset list                       what this build offers
-  tfg preset show <id>                  what it takes and what it would produce
-  tfg preset eject <id> > my.yaml       the recipe it stands for, to edit
-
-A preset is a recipe with a name. Ejecting one gives back an ordinary recipe
-file, so nothing here is a closed box.
-
-Run "tfg generate --preset <id>" to produce the files.
-`)
-}
-
-// presetFlagSet builds the flag set of an operation taking one preset id.
-//
-// The id has to be read before parsing, because the parameters of the preset
-// are flags and there is no way to register them until it is known which they
-// are.
-// asJSON is filled in for the operations that have a machine readable form and
-// nil for the one that does not - a recipe is already machine readable, and a
-// second encoding of it would be a second thing to keep in step.
-func presetFlagSet(name string, args []string, out, errOut io.Writer, usage func(io.Writer), asJSON *bool) (
-	*preset.Expansion, int) {
-
-	fs := flag.NewFlagSet("preset "+name, flag.ContinueOnError)
-	fs.SetOutput(errOut)
-	fs.Usage = func() { usage(errOut) }
-	if helpRequested(args) {
-		usage(out)
-		return nil, ExitOK
-	}
-	// Registered before the parameters, so a preset declaring one called json
-	// is caught by the collision check rather than by the flag package panicking.
-	if asJSON != nil {
-		fs.BoolVar(asJSON, "json", false, "write the answer as JSON to standard output")
-	}
-
-	id, rest := splitLeadingPath(args)
-	if id == "" {
-		fmt.Fprintf(errOut, "tfg: preset %s takes the id of one preset. Run \"tfg preset list\" to see them.\n", name)
-		return nil, ExitUsage
-	}
-	p, err := preset.Get(id)
-	if err != nil {
-		fmt.Fprintf(errOut, "tfg: %s\n", describeError(err))
-		return nil, classify(err)
-	}
-	if clash := clashingParameter(fs, p); clash != "" {
-		fmt.Fprintf(errOut, "tfg: the preset %s declares a parameter called %q and that is already a flag of this command. This is a fault in the build rather than in what you typed, and there is nothing you can do about it from here.\n", p.ID, clash)
-		return nil, ExitRuntime
-	}
-	registerPresetFlags(fs, p)
-
-	if err := fs.Parse(rest); err != nil {
-		return nil, ExitUsage
-	}
-	if fs.NArg() > 0 {
-		fmt.Fprintf(errOut, "tfg: preset %s takes one preset id and %q came after it. Give the parameters as flags, for example --limit 10mb.\n", name, fs.Arg(0))
-		return nil, ExitUsage
-	}
-
-	expanded, err := preset.Expand(id, givenPresetArgs(fs, p))
-	if err != nil {
-		fmt.Fprintf(errOut, "tfg: %s\n", describeError(err))
-		return nil, classify(err)
-	}
-	return expanded, ExitOK
-}
-
-func presetList(args []string, out, errOut io.Writer) int {
-	fs := flag.NewFlagSet("preset list", flag.ContinueOnError)
-	fs.SetOutput(errOut)
-	asJSON := fs.Bool("json", false, "write the list as JSON to standard output")
-	usage := func(w io.Writer) {
-		fmt.Fprint(w, `tfg preset list - the test questions this build can answer.
-
-Usage:
-  tfg preset list
-  tfg preset list --json
-
-Flags:
-`)
-		fs.SetOutput(w)
-		fs.PrintDefaults()
-		fs.SetOutput(errOut)
-	}
-	fs.Usage = func() { usage(errOut) }
-	if helpRequested(args) {
-		usage(out)
-		return ExitOK
-	}
-	if err := fs.Parse(args); err != nil {
-		return ExitUsage
-	}
-
-	all := preset.All()
-	if *asJSON {
-		list := make([]presetEntry, 0, len(all))
-		for _, p := range all {
-			list = append(list, presetEntryFor(p))
-		}
-		return renderJSON(list, out, errOut)
-	}
-
-	// An empty build says so rather than printing a heading over nothing.
-	if len(all) == 0 {
-		fmt.Fprint(out, "This build registers no presets.\n")
-		return ExitOK
-	}
-	fmt.Fprintf(out, "%-18s %s\n", "PRESET", "QUESTION IT ANSWERS")
-	for _, p := range all {
-		fmt.Fprintf(out, "%-18s %s\n", p.ID, p.Question)
-	}
-	fmt.Fprint(out, "\nRun \"tfg preset show <id>\" for what one takes and what it would produce.\n")
-	return ExitOK
-}
-
-func presetShow(ctx context.Context, args []string, out, errOut io.Writer) int {
-	usage := func(w io.Writer) {
-		fmt.Fprint(w, `tfg preset show - what a preset takes and what it would produce.
-
-The budget is counted from the plan, at the parameters you gave, so it is the
-number of files and bytes this run would really write.
-
-Usage:
-  tfg preset show size-boundaries
-  tfg preset show size-boundaries --limit 20mb --format png
-  tfg preset show size-boundaries --json
-`)
-	}
-	var asJSON bool
-	expanded, code := presetFlagSet("show", args, out, errOut, usage, &asJSON)
-	if expanded == nil {
-		return code
-	}
-
-	b, err := budgetOf(ctx, expanded)
-	if err != nil {
-		fmt.Fprintf(errOut, "tfg: %s\n", describeError(err))
-		return classify(err)
-	}
-
-	if asJSON {
-		entry := presetEntryFor(expanded.Preset)
-		entry.Budget = &b
-		entry.Defaulted = expanded.Defaulted
-		entry.Notes = expanded.Notes()
-		return renderJSON(entry, out, errOut)
-	}
-	describePreset(expanded, b, out)
-	return ExitOK
-}
-
-func describePreset(e *preset.Expansion, b budget, out io.Writer) {
-	p := e.Preset
-	fmt.Fprintf(out, "%s - %s\n%s\n", p.ID, p.Title, p.Question)
-
-	if len(p.Parameters) > 0 {
-		fmt.Fprint(out, "\nparameters:\n")
-		for _, param := range p.Parameters {
-			fmt.Fprintf(out, "  --%-12s %s\n", param.Name, param.Allowed())
-			if param.Detail != "" {
-				fmt.Fprintf(out, "  %-14s %s\n", "", param.Detail)
-			}
-		}
-	}
-	for _, name := range p.Reads {
-		fmt.Fprintf(out, "  --%-12s the global flag, this preset gives it a default\n", name)
-	}
-
-	fmt.Fprintf(out, "\nbudget at these values:\n  %s, %s, %s total, format %s\n",
-		core.Count(b.Targets, "target", "targets"), core.Count(b.Files, "file", "files"),
-		core.ExactBytes(b.Bytes), strings.Join(b.Formats, ", "))
-	for _, note := range e.Notes() {
-		fmt.Fprintf(out, "\nnote: %s\n", note)
-	}
-
-	if len(p.Catches) > 0 {
-		fmt.Fprint(out, "\nwhat it typically catches:\n")
-		for _, c := range p.Catches {
-			fmt.Fprintf(out, "  - %s\n", c)
-		}
-	}
-	fmt.Fprintf(out, "\nRun \"tfg preset eject %s\" for the recipe, or \"tfg generate --preset %s\" to produce the files.\n",
-		p.ID, p.ID)
-}
-
-func presetEject(args []string, out, errOut io.Writer) int {
-	usage := func(w io.Writer) {
-		fmt.Fprint(w, `tfg preset eject - the recipe a preset stands for.
-
-Prints an ordinary recipe file. Edit it, commit it, run it with tfg generate -
-from here on it is yours and nothing about it is special.
-
-The recipe goes to standard output and everything else to standard error, so
-"tfg preset eject size-boundaries > my.yaml" gives a clean file.
-
-Usage:
-  tfg preset eject size-boundaries > my.yaml
-  tfg preset eject size-boundaries --limit 20mb --format png > my.yaml
-`)
-	}
-	expanded, code := presetFlagSet("eject", args, out, errOut, usage, nil)
-	if expanded == nil {
-		return code
-	}
-
-	// The note goes to the error channel. The recipe is the data here, and a
-	// sentence about a number we chose has no business inside a file somebody
-	// is about to commit.
-	for _, note := range expanded.Notes() {
-		fmt.Fprintf(errOut, "note: %s\n", note)
-	}
-	if _, err := out.Write(expanded.Source); err != nil {
-		fmt.Fprintf(errOut, "tfg: cannot write the recipe: %s\n", describeError(err))
-		return ExitIO
-	}
-	return ExitOK
-}