fix(extism): convert bare top-level json.Number in FixJSONNumberTypes#117
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Closes #95 `engines/extism/internal/jsonHelpers.go:29-54` walks `map[string]any` and `[]any` shapes recursively to convert `json.Number` to a concrete Go type via the existing `convertJSONNumber` helper, but the `default:` case returned bare values unchanged. A `json.Number` arriving as the top-level value (not nested inside a map or slice) leaked through. A WASM module returning a plain integer at the top level — e.g. a `greet` exporting `42` — went through the extism evaluator's `json.Decoder.UseNumber()` and arrived at `result.Interface()` as `json.Number("42")`, not `int(42)`. The walking helper did its job for nested values but not for the outermost one. Add a `case json.Number:` branch ahead of the `default:` that delegates to the existing `convertJSONNumber` helper at lines 13-24. One-line behavioral fix; no new helper, no new behavior beyond making the recursion's leaf rule apply at the root. Tests: three subtests appended to TestFixJSONNumberTypes mirror the shape of the existing TestConvertJSONNumber cases — top-level integer → int, top-level decimal → float64, top-level invalid → unchanged json.Number. The existing "handles primitive types" subtest (lines 20-24) confirms `int`, `string`, and `bool` still pass through unchanged, guarding against the fix accidentally widening the converter. Out of scope: the exit-code-vs-output design question (#94); a WASM end-to-end regression test (would require new TinyGo source for a module that returns a top-level integer — disproportionate to a one-line helper fix).
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Pull request overview
This PR fixes Extism JSON output normalization by ensuring FixJSONNumberTypes converts a top-level json.Number (not just ones nested in maps/slices), preventing json.Number("42") from leaking to callers when a WASM module returns a bare number.
Changes:
- Add a
case json.Number:branch inFixJSONNumberTypesto apply the existingconvertJSONNumberleaf conversion at the root. - Add unit tests covering top-level integer, decimal, and invalid
json.Numberinputs.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| engines/extism/internal/jsonHelpers.go | Applies convertJSONNumber to top-level json.Number values in FixJSONNumberTypes. |
| engines/extism/internal/jsonHelpers_test.go | Adds regression tests for top-level json.Number conversion/preservation behavior. |
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* docs: add CHANGELOG.md (Keep a Changelog 1.1.0) Closes #102 Repo had no CHANGELOG.md; users had to read GitHub release notes to find what changed between versions. With v1 ahead and a queue of breaking changes (#86, #87, #88, #89, #90, #91, #104), having a CHANGELOG before landing those gives downstream code reviewers and IDEs visibility into what's coming. Format follows Keep a Changelog 1.1.0 with the standard six headings (Added / Changed / Deprecated / Removed / Fixed / Security). [Unreleased] section captures the run of merged-but-not-released PRs since v0.7.0: - #103 polyscript.New[E] generic constructor (deprecates 12 FromXxx) - #105 slog.Handler optional in engine subpackages - #106 RequestToMap mutation fix - #107 HTTP loader MaxBodySize cap - #110 unify nil-handler on slog.Default(); drop stdout fallbacks - #113 WithLogHandler(nil)/WithLogger(nil) → no-op - #114 drop redundant nil-guards; tighten WithLogHandler doc - #115 docs/LOGGING.md - #117 fix bare top-level json.Number leak - #118 WithGlobals additive; drop dead URL check - #119 extism Eval test coverage Backfilled the three releases the issue called out (v0.5.0, v0.6.0, v0.7.0) from existing GitHub release notes, sorted into Keep a Changelog categories. Earlier releases (v0.0.x through v0.4.0) intentionally not backfilled per the issue scope; can be added in a follow-up if desired. Out of scope: the optional CI gate that fails PRs not touching CHANGELOG.md. Adds noise to small bug PRs and wants opt-out-label infrastructure to support it; better as a separate issue. * docs(CHANGELOG): clarify deprecated FromXxx still take positional handler Copilot review noted that "no constructor demands a handler" is misleading because the deprecated FromXxx constructors still take a positional `logHandler slog.Handler` argument (even though nil is accepted). Reword to distinguish the new generic constructor (no handler arg) from the deprecated ones (still take it, but nil is OK). --------- Co-authored-by: Claude <noreply@anthropic.com>
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Summary
Fixes a bug where
FixJSONNumberTypesleft bare top-leveljson.Numbervalues unconverted, so a WASM module returning a plain integer at the top level (e.g.greetexporting42) leakedjson.Number("42")through to the caller'sresult.Interface()instead of arriving asint(42).The recursive walker at
engines/extism/internal/jsonHelpers.go:29-54correctly convertedjson.Numbervalues nested insidemap[string]anyor[]any, but thedefault:case returned bare values unchanged. The leaf rule wasn't applied at the root.Fix
One
casebranch ahead ofdefault:that delegates to the existingconvertJSONNumberhelper (lines 13-24, same file):No new helper. No new behavior beyond making the recursion's leaf rule apply at the root.
Tests
Three subtests appended to
TestFixJSONNumberTypes, mirroring the existingTestConvertJSONNumbercases:json.Number("42")→int(42)json.Number("3.14")→float64(3.14)json.Number("xyz")→ unchangedThe existing "handles primitive types" subtest (lines 20-24) already confirms
int,string, andboolpass through unchanged — that's the regression guard against the fix accidentally widening the converter.Out of scope
Test plan
go test -race -count=1 ./engines/extism/internal/...— greengo test -race -count=1 ./...— full suite greengo vet ./...— cleanCloses #95
https://claude.ai/code/session_01C61VEAmjxSnX5Xhbab8NvL
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