feat(go): emit Go parse tables from a spec, which is what Go has instead of a derive - #931
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…ead of a derive
Go has no macros. What a Rust CLI gets from `#[derive(Cli)]` at compile time, a
Go CLI has to get from a generator at build time, so `usage generate go` is the
same milestone for usage-go that usage-derive is for the Rust side — the point
at which a spec, rather than a hand-written table, is what a CLI is declared in.
//go:generate usage generate go -f mycli.usage.kdl -o tables.go
It emits binding tables and nothing else. Help text, choices, defaults and `env`
are absent for the same reason they are absent from the Rust hot path: a
successful parse never reads them, and mise's several hundred kilobytes of help
strings do not belong in front of a parser. A cold table is separate work.
The output is gofmt-clean as it comes out, which took some care and is worth it:
the alternative is every adopter running a formatter before they can commit, and
this repo's own CI failing `gofmt -l` on the table it will check in. gofmt pads
within runs of consecutive single-line entries and starts a new run after
anything spanning lines, so the emitter models a literal as a list of fields and
blocks rather than printing strings. Verified against mise's spec, usage's own,
and the examples spec: `gofmt -w` changes nothing in any of them.
What the generated file gives an author beyond speed is the key constants. An
event carries a Key, so generated code dispatches on `mise.FlagUseGlobal`
instead of comparing strings, and a flag that is renamed in the spec fails to
compile rather than silently never matching.
Three things resolved at generation time, so the parser reads one field per
command instead of walking: `unknown_flags` inheritance, `default_subcommand`
into a pointer at the node it names, and hidden aliases folded in beside visible
ones — hiding is a help-output concern and binding never reads it.
Identifier collisions are ordinary rather than exotic, and are handled: mise
declares both a `macos-defaults` command and a `macos defaults` path, and both
want to be spelled `CmdMacosDefaults`.
Checked end to end before committing, though the checked-in fixture that will
keep it honest is the next commit in this stack: the generated mise tables
compile, parse `mise use -g node@20`, resolve `x` to `exec` through its alias,
split `tasks run build extra --dry-run -- --verbose` across ARGS and ARGS_LAST,
and produce a package with no init function whose Root is a type D symbol — 211
commands and 711 flags that cost nothing before main.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Included review availability: Your plan includes up to 4 reviews per rolling hour; 0 remain after this review. 📝 WalkthroughWalkthroughAdds a Go parse-table emitter to the library and exposes it through a new ChangesGo generation flow
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to This PR adds build-time Go table generation and related documentation and tests; no actionable merge-blocking risk remains beyond normal checks and review. Sequence Diagram(s)sequenceDiagram
participant CLI as generate go CLI
participant GoRun as Go::run
participant Generator as go::generate
participant Output as stdout or output file
CLI->>GoRun: resolve file or inline spec
GoRun->>Generator: pass Spec and GoOptions
Generator-->>GoRun: generated Go source
GoRun->>Output: write source
Possibly related PRs
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jdx
changed the title
Greptile SummaryThe PR adds a Go parse-table generator and wires it into the CLI, generated references, and command-effect metadata. It also adds identifier sanitization, collision handling, inherited parser settings, and direct-child default-subcommand resolution.
Confidence Score: 4/5The PR is not yet safe to merge because a valid root alias/name collision can make generated Go tables select the wrong default command. The repaired lookup is restricted to root children, but its first-match collision behavior differs from the reference parser and can route omitted-command input into the wrong command. Files Needing Attention: lib/src/go/mod.rs Important Files Changed
Reviews (3): Last reviewed commit: "fix(go): reserve the suffixed identifier..." | Re-trigger Greptile |
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| fields.push("Variadic: true".to_string()); | ||
| if let Some(max) = arg.var_max { | ||
| fields.push(format!("VarMax: {}", clamp_var_max(max))); | ||
| } |
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Variadic flag VarMax ignored
Medium Severity
For a variadic flag argument like `--include <pattern>...`, KDL puts var_max on the flag, but flag_literal only reads arg.var_max. That leaves VarMax out of the generated table, so the Go parser treats the flag as unbounded and can consume positionals past the intended limit.
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Not changing this one — the two spellings are different questions, and the corpus pins them apart.
On the flag's argument it bounds one occurrence's values, which binding decides, and the emitter does emit it. That is corpus vector a-bound-stops-a-variadic-flag, labelled binding:
flag "--include <pattern>…" {
arg "<pattern>…" var=#true var_max=2
}{Key: FlagInclude, Name: "include", ..., Variadic: true, VarMax: 2}
On the flag it counts occurrences — --include a --include b — which no single token can decide, so it is a post-binding check. That is flag-var-too-many, labelled post-binding for exactly that reason.
usage-argv's own table builder splits it the same way (f.arg.as_ref().filter(|a| a.var).and_then(|a| a.var_max)), as does the derive, whose counts_occurrences narrows the check to a repeatable flag with a single-value argument. So reading arg.var_max here matches the grammar and both Rust implementations.
I have added a test pinning both halves so the question does not have to be re-derived next time.
This comment was generated by Claude Code.
… tree Three review findings on the emitter, one of which the checked-in mise tables in the next commit had already made visible: `Root.DefaultSubcommand` pointed at `oci run` rather than the top-level `run`. `default_subcommand` names a subcommand *of the root* — the spec declares it once at the top — but the resolution scanned every command in the tree and took the first match in depth-first order, which for mise is `oci run`. A parse would then have descended into a command that is not the root's child at all, so `mise build` would have run something under `oci`. The comment above the code already said "the root's own subcommands"; the code just did not do it, which is the version of this mistake that survives review easiest. The root's key was spelled rather than claimed, so a subcommand named `root` was handed `CmdRoot` too and the file declared the constant twice and would not compile. It goes through the same counter as everything else now, and gets `CmdRoot2` as any other collision would. A package name that is not a Go identifier produced a file that would not compile either — `--package my-pkg`, or a spec whose bin is `go` or `type`, both of which are plausible names for a CLI. Names derived from the spec are sanitized, since the author did not choose `bin` for this purpose and cannot be asked to fix it; an explicit `--package` is refused with a message instead, because quietly turning `my-pkg` into `mypkg` is a surprise waiting in somebody's build script. `is_valid_package` is public so the check and the sanitizing cannot drift. Not changed: the fourth finding, that a variadic flag's `var_max` is dropped. The two spellings are different questions and the corpus pins them apart. On the flag's *argument* it bounds one occurrence's values and belongs in the binding table, which is the corpus vector `a-bound-stops-a-variadic-flag`, and the emitter does emit it. On the flag itself it counts *occurrences*, which no single token can decide, so it is a post-binding check — `flag-var-too-many`, labelled post-binding for exactly that reason. usage-argv's tables and the derive's `counts_occurrences` split it the same way. A test now pins both halves so the question does not have to be re-derived next time. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Inline comments:
In `@lib/src/go/mod.rs`:
- Around line 93-106: Update GoNameGen::unique to ensure the generated
identifier itself is unused, not just the requested base: retry suffixes until
the candidate spelling is free, then reserve that candidate in self.taken before
returning it. Preserve the unsuffixed base when available and prevent collisions
such as a later base matching an earlier generated suffix.
- Around line 561-589: Update is_valid_package to reject the exact package names
"_" and "init", while preserving "__" as valid. Update package_ident so
sanitized results equal to either reserved name are prefixed with "cli",
alongside the existing empty, digit-starting, and keyword checks.
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lib/src/go/snapshots/usage__go__tests__a_default_subcommand_points_into_the_tree.snapis excluded by!**/*.snaplib/src/go/snapshots/usage__go__tests__a_whole_cli.snapis excluded by!**/*.snaplib/src/go/snapshots/usage__go__tests__colliding_names_get_distinct_identifiers.snapis excluded by!**/*.snaplib/src/go/snapshots/usage__go__tests__unknown_flags_are_inherited_and_overridable.snapis excluded by!**/*.snap
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cli/assets/fig.tscli/assets/usage.1cli/src/cli/generate/go.rscli/src/cli/generate/mod.rscli/src/command_effects.rscli/usage.usage.kdldocs/cli/reference/commands.jsondocs/cli/reference/generate.mddocs/cli/reference/generate/go.mddocs/cli/reference/index.mdlib/src/go/mod.rslib/src/lib.rs
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Instruction countsNothing was compared, and so nothing was gated. No series appears on both sides: either the base has no measurements recorded, or the two were measured on different runner classes, which are deliberately not comparable — counts shift between machine types by more than a real regression does. New, nothing to compare against: Only instruction counts gate. Wall clock is shown for context — on identical hardware it moves 4-20% run to run. Measured by tak — instruction-counted CLI benchmarks, stored in this repository's git notes. Shadow comparisonParsing
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… names Two follow-up findings on the emitter, both about emitting a file that does not compile. `unique` counted per base and never claimed the spelling it handed out, so a third command could be given an identifier the second had already taken: `macos-defaults` and `macos defaults` produce `CmdMacosDefaults` and `CmdMacosDefaults2`, and a command named `macos-defaults2` then asked for `CmdMacosDefaults2` directly and got it. It searches for a free candidate now and reserves it. The third lands on `CmdMacosDefaults22`, which is unlovely and unique; the test asserts no constant is declared twice rather than pinning the suffix scheme, which is the property that actually matters. `_` and `init` are refused as package names, for two different reasons that are worth keeping straight. `package _` is rejected where it is written — `invalid package name _`. `package init` declares perfectly well and cannot be *imported*: an import binds the package name as an identifier in file scope, and `init` may only be a func, so an importer gets `cannot import package as init - init must be a func`. A table package exists to be imported, so it is out either way. Both checked against the compiler rather than taken from the citation offered, which is about the import and would have had this rejecting `package init` for a reason that is not true. `__` stays valid, and only the exact names are reserved, so `initialize` is fine. `package_ident` now asks `is_valid_package` instead of repeating its conditions, so the sanitizer cannot come to disagree with the check about what is acceptable — and a test asserts that every name the sanitizer produces is one the validator accepts. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
| .find(|e| { | ||
| &e.cmd.name == name | ||
| || e.cmd.aliases.contains(name) | ||
| || e.cmd.hidden_aliases.contains(name) | ||
| }) |
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When a root command alias matches another root command's canonical name and default_subcommand uses that name, this first-match lookup selects the earlier command while the reference parser selects the later mapping, causing generated Go parsers to descend into and bind arguments for the wrong command.
Knowledge Base Used: Compiled argv parsing and derives
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Good catch on the behaviour, but I am not changing the emitter — this is a pre-existing disagreement between the two Rust implementations, and the emitter is matching the right one.
The two resolutions really do differ:
- usage-lib builds a lookup map, inserting
name → nameand thenalias → nameper subcommand in declaration order (SpecCommand::find_subcommand). A later canonical name overwrites an earlier alias, sorunresolves to the canonicalrun— the "later mapping" you describe. - usage-argv scans per candidate, checking name then aliases, and returns the first match (
find_subcommand, theconst fnthe Rust derive uses to resolvedefault_subcommandat compile time). So the earlier command wins by its alias.
The emitter feeds usage-argv's Go twin, and conformance/src/argv.rs resolves it the same per-candidate way. Changing it would make the Go parser disagree with the Rust parser it is a port of, in order to agree with a third implementation — and it would not even be self-consistent, because a typed run goes through the same per-candidate scan in both usage_argv::Parser::find_subcommand and the Go findNamed. The default_subcommand pointer would then select a different command than typing the word does.
So the divergence is in subcommand resolution generally rather than in default_subcommand, and it predates this PR. The repo already has a mechanism for exactly this — a corpus vector carrying a reference.diverges note, which conformance/tests/reference.rs then checks in both directions. That is where it belongs, and writing the vector means deciding which reading the grammar wants, which is a call for @jdx rather than something to settle inside a Go codegen PR. I have flagged it separately.
Worth adding that the spec being described here is arguably ill-formed anyway: one command's alias colliding with another's canonical name means the alias is unreachable in usage-lib and the canonical name is unreachable in usage-argv. A duplicate check at the level where the whole tree is visible — where Spec::to_kdl already checks duplicate flag forms and keys — would be the real fix.
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Understood — the emitter targets usage-argv (the per-candidate scan), and changing it to match usage-lib's map-based resolution would break consistency between default_subcommand pointer resolution and a typed subcommand name going through the same findNamed path. That's a real correctness argument, not just a style preference.
The original comment overfitted to usage-lib's behavior as the reference. You're right that the divergence predates this PR and belongs in a reference.diverges corpus note rather than here.
Shall I remember this as a rule: "when reviewing usage-argv or its Go emitter, treat usage-argv's per-candidate scan (not usage-lib's map-based resolution) as the authoritative reference for subcommand resolution behavior"?
…ft unnoticed (#932) The generator landed in #931 with snapshot tests over small fixtures, which prove it emits what it meant to and nothing about whether the result works. This is the other half: mise's committed spec, generated into `go/internal/shadow/mise`, checked in, and parsed against. Checked in rather than built by the test, for the two reasons the Rust shadows are — a reviewer can read the diff when the emitter's vocabulary changes, and CI runs `mise run gen-go` and fails if regenerating produces one. A change to the generator that nobody meant now has to be committed rather than discovered later. mise is the fixture because it is the largest usage CLI there is (211 commands, 711 flags, 128 positionals, four deep) and because every shape that has been awkward to express came from it. The cases are invocations out of its own docs, hand-written on purpose: what the generator produces is only worth checking if it parses the words users actually type. ## Two properties measured at scale rather than at fixture size **Keys are unique and dense.** Generated code dispatches on a `Key`, so two entries sharing one would bind the wrong field. The Rust derive hashes its way around this because two macro expansions cannot see each other; a generator sees the whole spec and can count, so a collision would be inexcusable rather than unlucky. Checked across all 989 entries. **A parse still allocates nothing.** A scope lookup that collected flags into a slice, or a walk that built one per token, is invisible on a spec with four flags and obvious on one with 711. **110 ns and 0 allocations** for `mise use -g node@20`. ## One case pins a hole rather than a property `run --wat` is `unexpected_arg`, because mise's spec gives `run` no positional at all — it clears them and adds `mount run="mise tasks --usage"`, so task names come from running that, and binding does not resolve mounts. When mounts are answered that case changes, and pinning it means it changes loudly. ## Also here The README's conformance count was stale on `main`: #926 imported the argv questions clap's suite answers, taking the corpus from 123 vectors to 152. The Go parser answers all **122** binding vectors, up from 101, **without a change** — which is a better advertisement for the corpus than the original number was. --- <sub>Stack created with <a href="https://github.com/github/gh-stack">GitHub Stacks CLI</a> • <a href="https://gh.io/stacks-feedback">Give Feedback 💬</a></sub> 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- CURSOR_SUMMARY --> --- > [!NOTE] > **Low Risk** > Mostly generated data, docs, CI, and tests; no runtime product behavior changes beyond guarding the Go emitter output. > > **Overview** > Adds **checked-in Go binding tables** for mise’s full spec under `go/internal/shadow/mise`, regenerated via **`mise run gen-go`** (`usage generate go` on `benches/mise.usage.kdl`), mirroring the Rust shadow workflow so emitter changes show up in review and CI. > > **CI** now runs `gen-go` and fails if `render`, `gen-shadow`, or `gen-go` leave a dirty tree. > > **Tests** on the shadow tables cover real mise invocations, **root `default_subcommand run`** (not `oci run`), **unique dense `Key`s** across ~1000 entries, and **zero allocations** at full CLI scale (plus a benchmark). **`go/README.md`** documents `//go:generate`, the shadow package, updated corpus counts (122 binding / 30 post-binding skipped), and drops the generator from “what is missing.” > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit dcd3446. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup> <!-- /CURSOR_SUMMARY --> --------- Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
Binding says which token becomes which flag or argument. This says
whether what landed is acceptable, and fills in what the command line
left empty.
**The corpus goes from 122 answered to 145 of 152.**
```
$ mise run test:go
152 vectors: 145 answered, 7 not yet
```
Follows #931 and #932. `required`, `choices`, the `env`-then-`default`
fallback, `var_min` and `var_max` all need to know something no single
token can tell you, which is why they were left out of the parser rather
than overlooked.
## Shape
They read a second, cold table — `Meta`, indexed by the same key the
parse table carries, so the two cannot drift on identity — and a program
that never applies them never touches it. The zero-allocation test now
covers a parse with metadata present, since the property that matters is
that binding does not reach for any of this.
Deliberately **not a framework**. `Fill` and `Check` are pure functions
over what binding produced, because the caller is the one that knows how
it accumulated: generated code assigns to a field, a harness with no
target type appends to a slice. Inventing a value model here would force
both through it.
## Three things the corpus settled that guessing would have got wrong
**An environment variable set to the empty string is set.** `EX_JOBS=`
is a value — treating empty as unset would make it mean something no
other empty value in the grammar means. The value is one token, never
re-split: quoting is the shell's job and there was no shell here at all.
**A flag that holds no value reads its variable as a yes or a no**, by
an allow-list — `1`, `true`, `True`, `TRUE` — matching usage-lib
exactly. So `yes`, `on` and `TrUe` are all false. Worth pinning rather
than discovering, since `EX_VERBOSE=0` meaning verbose would be a trap.
The corpus pins four cases; `TestEnvTruth` records the rest.
**`var_max` counts occurrences here, never values.** A variadic's
per-occurrence bound is a limit binding applies, so judging the total
again afterwards would fail an invocation that never broke it. (This is
the same distinction as the one discussed on #931.)
## What is left
Seven vectors, all relationships *between* flags — `conflicts`,
`overrides`, `required_unless` — which need a name resolved to the entry
it refers to. Listed by id with a reason rather than inferred from the
spec, because `overrides-loser-is-not-refilled-from-env` is as much an
env question as an overrides one and inference would have exempted
vectors nobody meant to exempt. The skip count is asserted against the
list, so it cannot become a way of hiding failures.
Also still open, and noted in the README: `usage generate go` emits the
parse tables but not the `Meta` ones, so these rules are reachable today
from a spec lowered at run time rather than from a generated package.
Proving them against the corpus came first, the way the binder did
before the generator.
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<!-- CURSOR_SUMMARY -->
---
> [!NOTE]
> **Medium Risk**
> Behavior changes CLI validation semantics (env, defaults, required,
choices, variadic bounds) and expands the conformance harness; parser
hot path is explicitly tested to stay zero-alloc, but adopters must call
the new APIs correctly.
>
> **Overview**
> Adds a **cold `Meta` / `Metadata` table** alongside the parse tables
and **`Fill` / `Check`** in `post.go` so binding stays allocation-free
while **required**, **choices**, **env → default** fallback,
**`var_min`**, and **flag `var_max` (occurrences)** are judged after the
last token. Post-binding failures reuse **`argv.Error`** with new codes
and fields (`Name`, `Choices`, `Bound`/`Got`).
>
> **`spec.Build()`** now emits parse tables and metadata in one pass
(shared keys); the JSON spec builder picks up the extra declaration
fields and usage-lib-aligned rules (defaults on nested arg values, no
nested `env`, choices on the value).
>
> **Conformance** runs post-binding vectors with per-vector env,
accumulates by flag/arg key along the command path, and documents **7
remaining** inter-flag vectors (`conflicts`, `overrides`,
`required_unless`) in an asserted `notYet` list. README updates the pass
count (**145 / 152**).
>
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
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Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
1 participant
Go has no macros. What a Rust CLI gets from
#[derive(Cli)]at compile time, a Go CLI has to get from a generator at build time — so this is the same milestone for usage-go that usage-derive is for the Rust side: the point at which a spec, rather than a hand-written table, is what a CLI is declared in.//go:generate usage generate go -f mycli.usage.kdl -o tables.goFollows #921 and #922, which landed the binder and the conformance suite.
Binding tables only
Help text, choices, defaults and
envare absent, for the same reason they are absent from the Rust hot path: a successful parse never reads them, and mise's several hundred kilobytes of help strings do not belong in front of a parser. A cold table is separate work.The output is gofmt-clean as it comes out
This took some care and is worth it — the alternative is every adopter running a formatter before they can commit, and this repo's own CI failing
gofmt -lon the table #932 checks in. gofmt pads within runs of consecutive single-line entries and starts a new run after anything spanning lines, so the emitter models a literal as a list of fields and blocks rather than printing strings.Verified against mise's spec, usage's own, and the examples spec:
gofmt -wchanges nothing in any of them.What the author gets beyond speed
The key constants. An event carries a
Key, so generated code dispatches onmise.FlagUseGlobalrather than comparing strings — and a flag renamed in the spec then fails to compile instead of silently never matching.Three things are resolved at generation time so the parser reads one field per command instead of walking:
unknown_flagsinheritance,default_subcommandinto a pointer at the node it names, and hidden aliases folded in beside visible ones (hiding is a help-output concern; binding never reads it).Identifier collisions are ordinary rather than exotic, and are handled: mise declares both a
macos-defaultscommand and amacos defaultspath, and both want to be spelledCmdMacosDefaults.Checked end to end
The fixture that keeps this honest in CI is #932, but before committing I confirmed the generated mise tables compile, parse
mise use -g node@20, resolvextoexecthrough its hidden alias, splittasks run build extra --dry-run -- --verboseacrossARGSandARGS_LAST, and produce a package with no init function whoseRootis a typeDsymbol — 211 commands and 711 flags that cost nothing beforemain.Stack created with GitHub Stacks CLI • Give Feedback 💬
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Note
Medium Risk
Large new code generator with many spec edge cases, but it is additive build-time output; mistakes would break adopters' generated Go compile/parse behavior rather than runtime security.
Overview
Introduces
usage generate go, the Go analogue of compile-time Rust derives: specs become check-in-ready Go source forgithub.com/jdx/usage/go/argv, typically via//go:generate usage generate go -f mycli.usage.kdl -o tables.go.The new
usage::goemitter writes binding-only tables (commands, flags, args, keys, aliases)—not help, choices, or defaults—using package-levelvartrees consumable by the linker withoutinit. Output is gofmt-aligned (const blocks and struct field runs). Generation resolvesunknown_flagsinheritance,default_subcommandagainst root direct children only (avoids wrong deep matches), folds hidden aliases into bindings, and deduplicates Go identifier collisions with suffixed names.The CLI accepts
-f/--spec,-o, and-p/--package; invalid explicit package names error instead of silent mangling. Spec metadata, man page, Fig completion, docs, and command read/write effects are updated for the new subcommand.Reviewed by Cursor Bugbot for commit 858445b. Bugbot is set up for automated code reviews on this repo. Configure here.
Summary by CodeRabbit
New Features
generate goto generate Go source code from a CLI usage specification.Documentation