feat(observable)!: make Observable.choose take a voption chooser, add ObservableOption

[xperiandri]

Proposed Changes

Part of splitting #22 into small pull requests that can be reviewed one at a time. It is stacked on #29 (feat/observable-of-seq), so it shows only its own change; merge #29 first.

Observable.choose always resolved to FSharp.Core's IObservable version (FS0001) after open FSharp.Control.R3, because the R3 variants were static members of types in AutoOpen modules nested inside the non-AutoOpen Observable module. Their [<Extension>] members also added .choose to every F# function value.

choose is now a function of the Observable module, which shadows FSharp.Core's Observable.choose. Like every function of the library that works with optional values it takes a voption chooser, which does not allocate. The option variant lives in the new ObservableOption module, which requires qualified access: ObservableOption.choose.

Types of changes

What types of changes does your code introduce to FSharp.Control.R3?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• Build and tests pass locally – 0 warnings, Fantomas is clean, and the tests that exist at this commit pass
• I have added tests that prove my fix is effective or that my feature works (if appropriate) – in test: cover the library with integration tests #22, the top of this stack
• I have added necessary documentation (if appropriate)

Further comments

Breaking change: the OptionExtensions and ValueOptionExtensions types are removed; Observable.choose takes 'T -> 'R voption, use ObservableOption.choose for 'T -> 'R option. After open FSharp.Control.R3, Observable.choose is the R3 function; use Microsoft.FSharp.Control.Observable.choose for IObservable and F# events.

Tests (in #22): the choose and ObservableOption choose tests of ObservableTests.fs, and the chunkByBoundaries scenarios of IntegrationTests.fs that feed choose.

Stack – every pull request is based on the one before it, so each shows only its own change. Merge them in this order:

1. refactor!: prefix AwaitOperationConfiguration cases with Await #23 refactor!: prefix AwaitOperationConfiguration cases with Await
2. fix: validate the concurrency limit of mapAsync options eagerly #24 fix: validate the concurrency limit of mapAsync options eagerly
3. fix(rxquery): emit yield/zero synchronously to keep element order #25 fix(rxquery): emit yield/zero synchronously to keep element order
4. fix(rxquery)!: stop seeding sumBy with Unchecked.defaultof #26 fix(rxquery)!: stop seeding sumBy with Unchecked.defaultof
5. feat(rxquery): add rxqueryWith to cancel the terminal query operators #27 feat(rxquery): add rxqueryWith to cancel the terminal query operators
6. docs(rxquery): document the query builder and every query operator #28 docs(rxquery): document the query builder and every query operator
7. feat(observable)!: make ofSeq reachable as Observable.ofSeq #29 feat(observable)!: make ofSeq reachable as Observable.ofSeq
8. feat(observable)!: make Observable.choose take a voption chooser, add ObservableOption #30 feat(observable)!: make Observable.choose take a voption chooser, add ObservableOption ← this pull request
9. feat(observable): add chunkByBoundaries for boundaries of any element type #31 feat(observable): add chunkByBoundaries for boundaries of any element type
10. fix(observable): validate every chunk length eagerly #32 fix(observable): validate every chunk length eagerly
11. docs: document the processing and chunk configuration types #33 docs: document the processing and chunk configuration types
12. docs(observable): correct misleading XML docs and document every function #34 docs(observable): correct misleading XML docs and document every function
13. fix(async)!: remove the ignored cancellationToken from toLookup #35 fix(async)!: remove the ignored cancellationToken from toLookup
14. fix(async)!: surface the original exception and cancellation from Async wrappers #36 fix(async)!: surface the original exception and cancellation from Async wrappers
15. fix: wait for iterAsync through ForEachAsync instead of CountAsync #37 fix: wait for iterAsync through ForEachAsync instead of CountAsync
16. fix: stop iterAsync reliably and never lose a failure of its action #38 fix: stop iterAsync reliably and never lose a failure of its action
17. fix(task)!: default ofTask configureAwait to true #39 fix(task)!: default ofTask configureAwait to true
18. feat(task)!: move toArray and toList into the Task.Observable module #40 feat(task)!: move toArray and toList into the Task.Observable module
19. docs: correct the Async and Task module docs and document every member #41 docs: correct the Async and Task module docs and document every member
20. docs: document the R3 1.3.1 limitations of bind, catch and mapAsync #42 docs: document the R3 1.3.1 limitations of bind, catch and mapAsync
21. test: categorize the tests per tested component #43 test: categorize the tests per tested component
22. test: cover the library with integration tests #22 test: cover the library with integration tests

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused API changes are internally consistent, documented, and correctly integrated into compilation order.

Review effort: Balanced
Findings: None

What changed in this PR

Introduces allocation-free voption filtering through Observable.choose while providing an option-based alternative.

Changes:

• Replaces extension-based choose APIs with module functions.
• Adds the qualified ObservableOption.choose.
• Updates project metadata and breaking-change documentation.

File	Description
src/​FSharp.Control.R3/​Observable.fs	Adds the voption-based Observable.choose.
src/​FSharp.Control.R3/​ObservableOption.fs	Adds the option-based variant.
src/​FSharp.Control.R3/​FSharp.Control.R3.fsproj	Includes the new source file.
CHANGELOG.md	Documents the API changes.
.github/​copilot-instructions.md	Adds the new module to the project structure.

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