fix(stdlib): align Json.getCases return type with Python output#279
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fix(stdlib): align Json.getCases return type with Python output#279
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The F# return type `string array` for `getCases` was inaccurate — Fable union types' `cases()` static method returns `list[str]`, not an FSharpArray. Pyright flagged the resulting `cases: Array[str] = ...` assignment as a type error in the generated Python (issue #278). Change the return type to `ResizeArray<string>` (which maps to Python `list`) and update the call site to use `.Count` instead of `.Length`. Both compile to `len(...)` so runtime behavior is unchanged. Also wire up pyright in CI to catch future regressions: add a `just pyright` recipe scoped to `build/stdlib`, run it in the build-and-test workflow, and bump pyright to 1.1.409. Fable codegen-artifact rules (`reportUnusedImport`, `reportInvalidTypeVarUse`) are disabled since those are emitted by the compiler, not the bindings. Closes #278 Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
getCasesreturnsAny | list[Unknown]instead ofArray[str]#278: pyright errorType "Any | list[Unknown]" is not assignable to declared type "Array"in the generatedbuild/stdlib/json.py.getCaseswas annotatedstring array(FSharpArray) in F#, but Fable union types'cases()method actually returns a Pythonlist— and the emit'slambda: []fallback returns a list too. Switched the F# return type toResizeArray<string>(which maps tolist[str]) and updated the call site to use.Countinstead of.Length. Both compile tolen(...), so runtime behavior is identical.just pyrightrecipe (depends onbuild, runsuv run pyright).build-and-test.ymlbetween build and test.[tool.pyright]scoped tobuild/stdliband switched tostandardmode (matches what downstream consumers run).reportUnusedImportandreportInvalidTypeVarUse— both are Fable codegen artifacts (unusedUNITimports, single-occurrence TypeVars from F# generics), not bindings issues.>=1.1.408→>=1.1.409.Verified by stashing the Json.fs fix and re-running
just pyright: the exact error from issue #278 reproduces. With the fix applied,0 errors, 0 warnings. All 524 Python tests still pass.Test plan
just buildsucceedsjust pyrightreports0 errors, 0 warnings, 0 informationsjust test-python— all 524 tests pass (17 json tests included)just pyrightreproduce the originalreportAssignmentTypeerror from Pyright type error in transpiled Json.fs:getCasesreturnsAny | list[Unknown]instead ofArray[str]#278🤖 Generated with Claude Code