docs(observable): correct misleading XML docs and document every function

[xperiandri]

Proposed Changes

Part of splitting #22 into small pull requests that can be reviewed one at a time. It is stacked on #33 (docs/processing-options), so it shows only its own change; merge #33 first.

Documentation only, apart from naming the mapi lambda parameters after the element and the index that R3 passes; the behaviour is unchanged.

• catch: the remark "Exception does not stop further processing" was wrong; the handler only sees terminal failures of its exception type, the failed source is not resumed and OnErrorResume passes through.
• concat: a |> concat b emits b first.
• bind: an inner failure fails the result only while the source runs.
• cast: an invalid cast is reported through OnErrorResume, and a null element cast to a value type as a NullReferenceException.
• skip/take: a negative count throws when called; take 0 completes at once without subscribing.
• The module, ofType and the error behaviour of map, filter and where are documented, and the copied typos ("identy", "upn", the question mark in take) are fixed.

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

Each corrected statement is pinned by a test of ObservableTests.fs in #22.

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
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 ← this pull request
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

🟡 Changes recommended

Some new documentation remains inaccurate for delayed inner failures and nullable value-type casts.

Review effort: Balanced
Findings: 3

Open (3)

• Document SelectMany completion behavior when the final inner sequence fails · New
• Clarify null cast exception behavior for non-nullable value types · New
• Use typeparamref for the generic result type in XML documentation · New

What changed in this PR

Improves XML documentation for observable operators while preserving behavior.

Changes:

• Documents operator semantics, failures, and edge cases.
• Clarifies mapi lambda parameter names.
• Updates changelog and repository guidance.

File	Description
src/​FSharp.Control.R3/​Observable.fs	Expands and corrects operator documentation.
CHANGELOG.md	Records the documentation correction.
.github/​copilot-instructions.md	Refines the Observable.fs description.

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