Harden jsonlit and reject unsupported syntax at Compile time#15
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jsonlit:
- Fix `[N][...]T` array-type detection so `[2][]int{{1},{2}}` and
`[3][4]int{{1,2,3,4}}` survive the rewrite (recursive
`isArrayTypeFollow`).
- Accept `<-` as a slice-type prefix follow so `[]<-chan T{}` passes
through.
- Treat `)`, `]`, and `}` as type-end tokens before `{` so
`func() {}`, `List[int]{}`, and `[]interface{}{1}` are not mangled
into bare object literals.
- Track a brace stack with three states (object, any-elemented typed,
inert typed) so nested type-omitted composites like
`[][]int{{1,2},{3,4}}` and `[]struct{X int}{{1},{2}}` are left
alone, while `map[string]any{"k": {"j": 1}}` and `[]any{{"k": 1}}`
still get the inner brace rewritten.
- Preserve comments inside empty `[]` by splitting the splice into
two edits.
- Add an `internal/jsonlit/README.md` describing the approach,
bracket and brace classification, and known limitations.
- Expand the test suite and fuzz seed corpus with the previously
broken shapes.
Compile-time validator:
- Add `validate.go` that walks the parsed AST and rejects every
unsupported form (function literals, slice expressions, type
assertions, channel ops, pointer/address ops, bitwise operators,
imaginary literals, spread args, generic instantiations, fixed-
size arrays, and typed slices/maps other than `[]any` /
`map[string]any`) with `ErrCompile` and a `line:col` prefix.
- Switch `Compile` to `parser.ParseExprFrom` with a local FileSet so
validator errors carry positions like the parser's own.
- Update three existing tests that previously asserted
`ErrEvaluate` for unsupported forms to now expect `ErrCompile`,
and update `docs/reference/spec.md` accordingly.
- Keep the runtime checks as defense in depth.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Two related improvements to the front-end of
expr:jsonlit edge cases. The token-based JSON-style rewrite in
internal/jsonlithad several shapes where valid Go input either failed to parse or was silently miscompiled. Fixed by makingisArrayTypeFollowrecursive (for[N][...]T), accepting<-/)/]as type-end tokens before{(for[]<-chan T{},func() {},List[int]{},[]interface{}{1}), tracking a brace stack so nested type-omitted composites like[][]int{{1,2}}and[]struct{X int}{{1}}are left alone whilemap[string]any{"k": {"j": 1}}still gets the inner brace rewritten, and splitting the empty-[]edit into two splices so comments are preserved. Adds aninternal/jsonlit/README.mddescribing the approach, classification, and known limits.Compile-time validation. Adds a one-pass AST validator (
validate.go) invoked fromCompileimmediately after parsing. Forms expr does not evaluate (function literals, slice expressions, type assertions, channel/pointer/address ops, bitwise operators, imaginary literals, spread args, generic instantiations, fixed-size arrays, typed slices/maps other than[]any/map[string]any) now fail atCompilewithErrCompileand aline:colprefix, instead of failing atRunwithErrEvaluate. SwitchesCompiletoparser.ParseExprFromfor positioned errors. Runtime checks are kept as defense in depth.Three existing tests previously asserting
ErrEvaluatefor unsupported syntax now expectErrCompile.docs/reference/spec.mdis updated accordingly.Test plan
go test ./...passesgo test -fuzz=FuzzRewrite -fuzztime=30s ./internal/jsonlit/clean (with new seeds for the previously broken shapes)go test -fuzz=FuzzCompile -fuzztime=20s .clean (>1M execs)go test -fuzz=FuzzEval -fuzztime=20s .clean (>400k execs)validate_test.gopins each unsupported form toErrCompileplus three nested-rejection casesinternal/jsonlit/jsonlit_test.goadds explicit cases for every fixed shape🤖 Generated with Claude Code