[All] Add missing Array, List, and Seq random choice/shuffle/sample members and tests by ncave · Pull Request #4488 · fable-compiler/Fable

ncave · 2026-04-05T08:13:43Z

[All] Add missing Array, List, and Seq random choice/shuffle/sample members and tests
[Dart/Rust] Add missing System.Random implementations and tests

…`, `randomShuffleInPlaceWith`, `randomShuffleInPlace`

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Pull request overview

Adds the missing randomChoice / randomShuffle / randomSample (and *By/*With variants) across Array, List, and Seq for multiple Fable targets, along with cross-target test coverage. Also introduces/updates System.Random implementations (notably Dart + Rust) and updates changelogs accordingly.

Changes:

Implement Array/List/Seq random APIs in the TS, Python, Dart, and Rust libraries; add Beam compiler replacements + Erlang implementations.
Add test coverage for the new APIs across Rust, Python, JS, Dart, and Beam test suites.
Add a Dart System.Random runtime implementation and adjust Dart/Rust random-related plumbing and changelog entries.

Reviewed changes

Copilot reviewed 37 out of 37 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
tests/Rust/tests/src/ArrayTests.fs	Adds tests for `Array.randomShuffleInPlace*`.
tests/Python/TestSeq.fs	Adds tests for `Seq.random*` APIs.
tests/Python/TestList.fs	Adds tests for `List.random*` APIs.
tests/Python/TestArray.fs	Adds tests for `Array.random` + `randomShuffleInPlace`.
tests/Js/Main/SeqTests.fs	Adds JS target tests for `Seq.random*` APIs.
tests/Js/Main/ListTests.fs	Adds JS target tests for `List.random*` APIs.
tests/Js/Main/ArrayTests.fs	Adds JS target tests for `Array.random` + `randomShuffleInPlace`.
tests/Dart/src/SeqTests.fs	Adds Dart target tests for `Seq.random*` APIs.
tests/Dart/src/ListTests.fs	Adds Dart target tests for `List.random*` APIs.
tests/Dart/src/ArrayTests.fs	Adds Dart target tests for `Array.random` + `randomShuffleInPlace`.
tests/Dart/src/ArithmeticTests.fs	Enables/adjusts Dart `System.Random` test strategy to compare seeded streams.
tests/Beam/SeqTests.fs	Adds Beam target tests for `Seq.random*` APIs.
tests/Beam/ListTests.fs	Adds Beam target tests for `List.random*` APIs.
tests/Beam/ArrayTests.fs	Adds Beam target tests for `Array.random` + `randomShuffleInPlace`.
src/Fable.Transforms/Dart/Replacements.fs	Adds Dart Array.Contains replacement + updates Dart `System.Random` ctor handling.
src/Fable.Transforms/Dart/Fable2Dart.fs	Maps `System.Random` to Dart library type reference.
src/Fable.Transforms/Beam/Replacements.fs	Adds Beam replacements for `Array`/`List` random APIs.
src/Fable.Compiler/CHANGELOG.md	Updates changelog entries to reflect “All” random APIs and Dart/Rust Random work.
src/Fable.Cli/CHANGELOG.md	Same changelog updates as compiler changelog.
src/fable-library-ts/Seq.fs	Implements `Seq.random*` in TS library via Array helpers.
src/fable-library-ts/List.fs	Implements `List.random*` in TS library via Array helpers.
src/fable-library-ts/Array.fs	Implements `Array.random` + `randomShuffleInPlace` in TS library.
src/fable-library-rust/src/Seq.fs	Implements `Seq.random*` via Array helpers (in-place shuffle for perf).
src/fable-library-rust/src/Random.rs	Refactors Rust Random implementation around `RngImpl` + `LrcPtr`.
src/fable-library-rust/src/List.fs	Refactors `List.random*` to delegate to Array implementations.
src/fable-library-rust/src/Array.fs	Adds `randomShuffleInPlace*` and aligns empty-source error messages.
src/fable-library-rust/Cargo.toml	Updates `rand` feature flags used by Rust library.
src/fable-library-py/fable_library/Seq.fs	Implements `Seq.random*` in Python library via Array helpers.
src/fable-library-py/fable_library/List.fs	Implements `List.random*` in Python library via Array helpers.
src/fable-library-py/fable_library/Array.fs	Implements `Array.random` + `randomShuffleInPlace` in Python library.
src/fable-library-py/fable_library/array_.py	Adds Python runtime implementations for `Array.random*` functions.
src/fable-library-dart/Seq.fs	Implements `Seq.random*` in Dart library via Array helpers.
src/fable-library-dart/Random.dart	Adds Dart runtime `System.Random` implementation.
src/fable-library-dart/List.fs	Implements `List.random*` in Dart library via Array helpers.
src/fable-library-dart/Fable.Library.Dart.fsproj	Includes `Random.dart` in the Dart library package.
src/fable-library-dart/Array.fs	Implements `Array.random` + `randomShuffleInPlace` in Dart library.
src/fable-library-beam/fable_list.erl	Adds Erlang implementations for list-based random APIs used by Beam replacements.

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src/fable-library-rust/src/Random.rs

src/fable-library-py/fable_library/array_.py

src/fable-library-dart/Random.dart

…mple members and tests

ncave · 2026-04-05T08:46:24Z

@dbrattli Do you mind taking a quick look at the Beam and Python changes (only if you have some spare time, of course).

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Pull request overview

Copilot reviewed 38 out of 38 changed files in this pull request and generated 1 comment.

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src/fable-library-rust/Cargo.toml

dbrattli · 2026-04-05T09:05:19Z

@ncave Nice additions. I can review and help out more this evening. Python type error are most likely caused by missing type stubs in array.pyi file (needed for the type checker to know about the new functions in array.rs).

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Pull request overview

Copilot reviewed 39 out of 39 changed files in this pull request and generated 4 comments.

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src/fable-library-py/src/array.rs

src/fable-library-rust/Cargo.toml

…errors Review follow-ups for #4488: Python: - Delete orphaned fable-library-py/fable_library/Array.fs (not in fsproj, declared module ArrayModule, never compiled). - Replace bare PyException("argname") raises in Rust extension with PyValueError carrying descriptive messages aligned with dotnet/fsharp FSharp.Core resource strings. Randomizer validation now matches .NET's dynamic format exactly, including the actual returned value. - Fix core/array.pyi: change Callable[[], float] -> Callable[[], SupportsFloat] for all 15 random *_by signatures. Fable transpiles F# (fun () -> 0.0) as returning Float64, which caused 13 pyright errors in test_array.py. Beam: - Align randomizer error message with .NET's dynamic format via io_lib:format. - Use andalso in random_sample_by guard (idiomatic Erlang). - Refactor random_choices_by: drop lists:map + lists:seq + lists:nth O(n) per-pick and use a tail-recursive choices_loop/5 helper with list_to_tuple for O(1) indexed access, matching the pattern used by shuffle_loop and sample_loop in the same file. Verification: - cargo check fable-library-core: clean - ./build.sh test python: 2233 passed, 0 failed - pyright on temp/tests/Python/: 0 errors (was 13) - ./build.sh test beam: 2390 passed, 0 failed Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dbrattli · 2026-04-05T15:08:18Z

@ncave See #27

…errors (#27) Review follow-ups for fable-compiler#4488: Python: - Delete orphaned fable-library-py/fable_library/Array.fs (not in fsproj, declared module ArrayModule, never compiled). - Replace bare PyException("argname") raises in Rust extension with PyValueError carrying descriptive messages aligned with dotnet/fsharp FSharp.Core resource strings. Randomizer validation now matches .NET's dynamic format exactly, including the actual returned value. - Fix core/array.pyi: change Callable[[], float] -> Callable[[], SupportsFloat] for all 15 random *_by signatures. Fable transpiles F# (fun () -> 0.0) as returning Float64, which caused 13 pyright errors in test_array.py. Beam: - Align randomizer error message with .NET's dynamic format via io_lib:format. - Use andalso in random_sample_by guard (idiomatic Erlang). - Refactor random_choices_by: drop lists:map + lists:seq + lists:nth O(n) per-pick and use a tail-recursive choices_loop/5 helper with list_to_tuple for O(1) indexed access, matching the pattern used by shuffle_loop and sample_loop in the same file. Verification: - cargo check fable-library-core: clean - ./build.sh test python: 2233 passed, 0 failed - pyright on temp/tests/Python/: 0 errors (was 13) - ./build.sh test beam: 2390 passed, 0 failed Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dbrattli · 2026-04-06T04:33:46Z

@ncave See #28

…ate (#28) Rewrote fable_random.erl to use Erlang's functional rand API (seed_s/uniform_s) with per-instance state stored in the process dictionary, keyed by make_ref(). This fixes the bug where creating a second Random(seed) instance would reset the global PRNG state, breaking independent seeded sequences. Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ncave added 3 commits April 4, 2026 13:30

[Dart] Implement System.Random

044e534

[Rust] Add missing Array members and tests: `randomShuffleInPlaceBy…

148ea20

…`, `randomShuffleInPlaceWith`, `randomShuffleInPlace`

[Rust] Simplified System.Random implementation

830bbb4

ncave changed the title ~~Random~~ [All] Add missing Array, List, and Seq random choice/shuffle/sample members and tests Apr 5, 2026

ncave requested a review from Copilot April 5, 2026 08:14

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[All] Add missing Array, List, and Seq random choice/shuffle/sa…

664bb6c

…mple members and tests

ncave force-pushed the random branch from 5481a25 to 664bb6c Compare April 5, 2026 08:44

ncave requested a review from Copilot April 5, 2026 08:58

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Added type defs

224c915

ncave force-pushed the random branch from 4405805 to 224c915 Compare April 5, 2026 09:31

Fix maxValue validation

e870773

ncave requested a review from Copilot April 5, 2026 09:40

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dbrattli mentioned this pull request Apr 5, 2026

[Python/Beam] Align random* error messages with .NET and fix pyright errors ncave/Fable#27

Merged

dbrattli and others added 3 commits April 5, 2026 11:15

[Python] Fix System.Random seeded implementation

9f4747e

[All] Added random probability distribution tests

e431d94

This was referenced Apr 6, 2026

[JavaScript / Python] Make a pass to implement missing pre-defined Date format #3976

Open

[Repo Assist] chore: add Dependabot configuration for automated dependency updates #4489

Open

[Repo Assist] Monthly Activity 2026-04 #4471

Open

dbrattli and others added 2 commits April 5, 2026 21:44

[Rust] Update dependencies

4066744

ncave force-pushed the random branch from 4d042cb to 4066744 Compare April 6, 2026 04:53

ncave merged commit 69c15cc into fable-compiler:main Apr 6, 2026
24 checks passed

ncave deleted the random branch April 6, 2026 05:04

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