Lets an agent type-check a DSL expression before spending a full input
pass. `mlr put --explain '...'` (and filter) runs the existing
parse -> ValidateAST -> CST build -> Resolve path, then:
- valid: prints "mlr {put,filter}: DSL expression is valid." and exits 0
- invalid: returns the build error up the normal path, so --errors-json
emits a structured document; exits 1
- -W with fatal warnings: reports and exits 1
The gate lives in the pass-two constructor, before any input file is
opened, so no input stream is read (verified with a nonexistent input
file still validating OK).
Also categorize bare "parse error: ..." messages from the DSL parser as
kind "dsl-parse-error" rather than "generic" (climain/errors_json.go),
so --explain --errors-json gives an agent a useful error kind. The CSV
reader's "parse error on line ..." is stream-time and never reaches this
command-line-parse categorizer.
Tests: dsl-explain/0001-0004 regression cases (valid put/filter, invalid
plain, invalid --errors-json) and categorize unit tests. Regenerated
verb docs, manpage, and the help usage-verbs golden case.
The older -X ("exit after parsing") still exits 0 even on a parse error;
left as-is since --explain is the correct validation path.
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
* Tier-2 structured verb options: OptionSpec, initial migration (#2098)
PR 3 of the AI-friendly roadmap (plans/plan-2098-llm.md).
Infrastructure:
- Add OptionSpec{Flag,Arg,Type,Desc,Repeatable,Values} to
pkg/transformers/aaa_record_transformer.go alongside TransformerSetup.
Type is one of: bool, string, int, float, csv-list, regex, filename,
format, enum. For type=="enum", Values lists the valid choices.
- Add Options []OptionSpec to TransformerSetup (nil = not yet migrated).
- Emit Options in VerbInfoForJSON (omitempty so unmigrated verbs stay
backward-compatible; agents check key presence for Tier-2 availability).
UsageText is always present as the Tier-1 prose fallback.
- Add VerbOptionsNilCheck() in aaa_verb_options_check.go: progress report
of migrated vs. unmigrated verbs, analogous to FLAG_TABLE.NilCheck().
- Wire verb-options-nil-check into mlr help (internal/docgen section).
Initial migration (5/70 verbs):
- nothing: empty Options (no verb-specific options, explicitly migrated)
- cat: -n (bool), -N (string), -g (csv-list), --filename, --filenum (bool)
- head: -g (csv-list), -n (int)
- tail: -g (csv-list), -n (int)
- tee: -a, -p (bool)
Tests:
- 5 new unit tests in aaa_transformer_json_test.go covering migrated/
unmigrated paths, field population, JSON round-trip, and key-presence.
- Regression test case 0003: mlr help verb-options-nil-check golden output.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
* Migrate all 70 verbs to structured OptionSpec; bump catalog schema to v2
Completes the Tier-2 migration started in the previous commit. Every verb
in TRANSFORMER_LOOKUP_TABLE now has a non-nil Options field.
- Workflow-migrated all 65 remaining verbs. Each Setup var now carries
Options: []OptionSpec{...} with Flag/Arg/Type/Desc fields. Verbs with
no verb-specific options (altkv, check, group-like, nothing, etc.) use
an empty slice to signal "migrated but no options."
- Drop `omitempty` from VerbInfoForJSON.Options: empty slices were silently
dropped, making migrated-no-option verbs indistinguishable from unmigrated
ones in JSON. Without omitempty: null=unmigrated, []=migrated-no-options,
[...]= migrated-with-options. Bump catalogSchemaVersion 1→2 for this shape
change.
- Replace the two "unmigrated-verb" unit tests (which used stats1 as an
example) with TestAllVerbsFullyMigrated (asserts every verb has non-nil
Options) and TestAllVerbsHaveOptionsKeyInJSON (asserts every migrated
verb emits the "options" key in JSON).
- Regenerate test/cases/cli-help/0003/expout: now reads
"Verb options migration: 70/70 migrated."
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
* Add --errors-json structured error output (#2098)
PR 4 of the AI-friendly roadmap (plans/plan-2098-llm.md).
Agents previously had to regex-match English prose to branch on error
kind; this PR lets them do it structurally.
Interface:
- mlr --errors-json <bad command> emits a JSON object to stderr and
exits 1; same behavior as prose path but machine-readable.
- MLR_ERRORS_JSON=1 (truthy) is the env-var equivalent.
- Without the flag, prose output is byte-for-byte unchanged.
JSON shape: {error, kind, token, verb, hint, did_you_mean[]}
Error kinds: unknown-verb, unknown-flag, verb-option-error, generic.
Implementation:
- New pkg/climain/errors_json.go: CLIError typed error, StructuredError
DTO, WantErrorsJSON pre-scan, Levenshtein edit distance, topMatches,
EmitStructuredError.
- Convert two direct os.Exit sites in parseCommandLinePassOne (unknown
verb, unknown flag) to return CLIError values; verb-option-error
likewise returns CLIError from pass-one ParseCLIFunc handling.
- parseCommandLinePassOne gains an error return; ParseCommandLine
propagates it.
- entrypoint.go pre-scans os.Args for --errors-json before calling
ParseCommandLine; routes errors to EmitStructuredError or printError.
- did_you_mean: Levenshtein nearest-match over verb catalog, flag
catalog, or the verb own OptionSpec flags (PR3 catalog) for
verb-option-error. Closes the self-correction loop the catalog
enables.
- --errors-json registered in Miscellaneous flags so it appears in
mlr --help and is not treated as an unrecognized flag.
Tests: 16 unit tests covering Levenshtein, topMatches, threshold,
WantErrorsJSON, CLIError interface, and all categorize paths.
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
