Add F# code snippets (Ctrl+K,Ctrl+X / Ctrl+K,Ctrl+S) by xperiandri · Pull Request #20521 · dotnet/fsharp

xperiandri · 2026-09-11T07:42:18Z

F# had no code snippets in Visual Studio. Ctrl+K,Ctrl+X now inserts a snippet, Ctrl+K,Ctrl+S surrounds a selection, and a snippet shortcut expands on Tab. The built-in catalog matches C#'s.

Not in scope: snippet shortcuts in IntelliSense completion, localized snippet folders, <Imports>/<References> and test-method snippets.

Details

The catalog covers declarations, members, control flow and computation expressions. ctor/equals fill in the enclosing type name, and match generates the cases of the union or enum it is given.

Verified by hand in the experimental hive in addition to the added tests.

🤖 Generated with Claude Code

github-actions · 2026-09-11T07:42:29Z

✅ Release notes checked

✅ Found changes and release notes in following paths:

Change path Release notes path Description

`vsintegration/src` docs/release-notes/.VisualStudio/18.vNext.md

xperiandri · 2026-09-11T10:08:27Z

xperiandri · 2026-09-11T14:48:18Z

/azp run fsharp-ci

azure-pipelines · 2026-09-11T14:48:24Z

Commenter does not have sufficient privileges for PR 20521 in repo dotnet/fsharp

T-Gro

🤖 🕵️ AI review — verify independently.

T-Gro

🤖🕵️ If this fixes an issue or implements an RFC/suggestion, link it (Fixes #... when applicable). Otherwise, give a short management-level summary in simplified technical English: what user scenario improves and what this achieves.

Please apply this PR-description guidance. Remove the implementation inventory already visible in Files, but keep necessary scope, compatibility, and dependency caveats.

xperiandri · 2026-09-14T15:19:00Z

Rewrote per the guidance — description is now Fixes #1498 + one paragraph on user-visible behavior + scope/compatibility caveats, implementation inventory removed.

T-Gro

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github-actions · 2026-09-27T22:38:22Z

🔍 Tooling Safety Check — Affects-Bootstrap, Affects-Build-Infra, Affects-Design-Time, Affects-Test-Tooling
Affects-Bootstrap: Changes compiler-service parsing components.
Affects-Build-Infra: Changes Visual Studio project build inputs.
Affects-Design-Time: Adds Visual Studio snippet execution paths.
Affects-Test-Tooling: Changes editor integration-test infrastructure.

Generated by PR Tooling Safety Check · gpt56 1.1M · ◷

T-Gro

🤖 🕵️ Re-reviewed all recent changes as of f2ab60b; 2 findings

T-Gro

🤖 🕵️ Re-reviewed all recent changes as of b542aee; 2 findings

T-Gro

🤖 🕵️ Re-reviewed all recent changes as of c282521; LGTM

Insert Snippet and Surround With have had nothing to offer in an F# file: the Code Snippets Manager has no F# entry and this repository contains no `.snippet` file at all. Adds 40 snippets covering the part of the C# set that has an F# analogue - declarations, members, control flow, computation expressions - together with the registration and packaging that lets Visual Studio find them. `Languages\CodeExpansions\FSharp` is written into the pkgdef rather than produced by `ProvideLanguageCodeExpansionAttribute`, which does not expose the `Package` value that `DisplayName` resolves against; C#, VB, XAML, XML and TypeScript all register by hand for the same reason. Only 1033 is registered, and outright rather than as `%LCID%`: registering both would enumerate every snippet twice on an English VS. The shipped directory is `Snippets\1033\FSharp`, not `Visual F#`, because a '#' in a VSIX part URI reads as a URI fragment and the packaging step refuses it. `SnippetsIndex.xml` supplies the folder name the Code Snippets Manager shows. Bodies are authored at column 0 with 4-space relative indentation - absolute indentation is applied at insertion time - and every snippet carries an explicit `$end$`, which is what lets the expansion client avoid reading the snippet XML back out of the live session. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Insert Snippet (Ctrl+K,Ctrl+X), Surround With (Ctrl+K,Ctrl+S), Tab expansion of a snippet shortcut, and the keys that drive a live expansion session. Nothing here reuses Roslyn: its snippet stack is `internal` under `LanguageServices.Implementation.Snippets` with no ExternalAccess surface, so F# writes its own `IVsExpansionClient` the way it already writes its own brace completion. The commands come in through one MEF `ICommandHandler<_>` part, ordered after the completion handler so that Tab still commits an open completion list first. Indentation is the F#-specific part. The expansion engine inserts snippet text verbatim, and C# gets away with that because Roslyn's formatter reflows the result afterwards; F# has no formatter, so `FormatSpan` computes the columns. That arithmetic lives in `SnippetIndentation`, free of editor types so that it can be tested on its own - the policy is where the mistakes live, not the buffer edit that applies it. A directive wrapper is its own line kind: `#if`/`#else`/`#endif` and the scoped `#nowarn`/`#warnon` pair read at the left margin whatever they wrap, so the code they cover keeps the column it had. Two things worth knowing for anyone reading `IVsExpansionClient` next to Roslyn's: `tsInsertPos` is the range `InsertNamedExpansion` replaces, so handing it the selection deletes the code a SurroundsWith snippet was meant to wrap; and `GetFieldSpan "selected"` does not answer for that special literal, so the substituted range is derived from the template's own `$selected$` line plus the line count the command handler took before the insertion. `ClassName()` and `GenerateMatchCases()` back the `ctor`, `equals` and `match` snippets. Both are synchronous COM callbacks, so they block; `ClassName()` blocks on a parse and `GenerateMatchCases()` on the stale-tolerant check-results path, falling back to a visible `| _ -> ()` rather than waiting unbounded. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

A RequireQualifiedAccess union rejects a bare case pattern (`A`, not `U.A`) - the generated pattern binds a fresh variable instead of testing the case, so it takes the first arm regardless of the actual value. matchRulesFor now qualifies with the entity's DisplayName when the union carries the attribute, the same way it already does for enums. ClassName() used the navigation item's LogicalName, which is qualified by every enclosing module ("Outer.C") - it does not resolve from a constructor sitting inside C's own scope. Strips to the name after the last '.'. GenerateMatchCases() resolved the lexer symbol nearest the field's end position, which is whatever identifier happens to sit there - for `f x`, that is `x`, not the call `f x`. Reads the type the checker captured for the field's whole span instead (TryGetCapturedType), so it matches the expression's own result type regardless of its shape. Surround With reindented every non-first selected line uniformly, including a line that is itself inside a multi-line string continued from an earlier selected line - inserting indentation there changes the string's value, not just its position. classifyLines now threads the lexer's color state across the span and classifies such a line as InsideString, left untouched like a blank line. lock.snippet closed the lambda on the same line as $selected$$end$, so a selection whose last line ends in a trailing // comment swallowed the closing paren into the comment, leaving the call unclosed. Moved onto its own line, matching how the other wrapping snippets already close. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

A match on a union or enum now spells its cases with the shortest qualifier that resolves at the insertion point, asked of the checked file the way the simplify-names analyzer asks it, instead of assuming `DisplayName.` is reachable: a `[<RequireQualifiedAccess>]` union in an unopened module produced `U.A`, which does not resolve. The expression's captured type is used as it stands, so matching a function value no longer generates the arms of its result type. Indentation is measured in visual columns. A snippet expanded after a tab took the character count as its column and came out one space in, and Surround With over tab-indented code wrapped it at the wrong column. A cancelled Surround With never reports back, so its pending selection was still set when the next shortcut expanded; the shortcut path now clears it. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Expands and surrounds like `task`, for code that has to run off the caller's context. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

The catalog test substitutes each literal's XML default, so it never ran `ClassName()` or `GenerateMatchCases()`. The match-rule core now takes the range of the expression, which lets a test hand it a document and a range without the expansion engine's COM span, and the new tests cover the names and case spellings the earlier review rounds found wrong: a type in nested modules, qualified and unqualified unions and enums, a call, a function value and a plain value. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…de fix `SourceText.LineBreakAt` now walks back to the nearest line that has a break, the way the code fix's private helper did, so a match inserted on the last line of a CRLF file no longer falls back to the host's line ending. The code fix uses it instead of its own copy. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

- Directive and string-continuation lines are what the F# lexer says they are: the hand-written directive prefixes and lexer-state list are gone. The snippet's own lines and the selected ones are lexed apart, so a region the selection leaves open no longer moves the wrapper's `#endif`, and `$$"""` continuations are recognised. - Surround With takes the wrapper's column from the selected code only, not from directive lines or string content in it. - `FormatSpan` delegates to a `Reindent` built from named steps instead of a narrated comment. - `ClassName()` walks the parse tree with `ParsedInput.tryPickLast`, and also answers in signature files; `GenerateMatchCases()` uses `DisplayName`, so cases that need backticks get them. - Editor options, out-parameter tuples, `RoslynHelpers` range conversions and `tryGetDocument` are reused instead of re-implemented; the pending Surround With selection is passed along rather than reset in three places. - Comments that restated the code are removed; tests are table-driven. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

- `GenerateMatchCases()` writes a case by its logical name, quoted when it is not a plain identifier. `DisplayName` decoded a case named `op_Nil` into the operator it encodes, which is not a pattern. - Selected lines that a SurroundsWith template places inside a string it opens itself are that string's content again, so they are no longer indented. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

T-Gro

🤖 🕵️ Re-reviewed all recent changes as of f8cc909; 2 findings

T-Gro

The diff is still way too big - apply the NoBloat instructions and CodeCompaction skill.

Especially the massive code comments would benefit not just with drastic reduction, but ideally with well named functions/arguments/bindings/types making the intention clear.

If a well named piece of code just tells what the comment says - delete the comment.

This diff adds 80 new code comment lines and 6800 new code comment chars.
Comments bypass the type system and become stale maintenance state. Keep only durable public contracts; express implementation intent through names, functions, active patterns, discriminated unions, and types.

T-Gro

🤖🕵️ AI review — verify independently.

… string whole - `GenerateMatchCases()` writes the cases of a list as `[]` and `_ :: _`. The names they are stored under, `op_Nil` and `op_ColonColon`, are not patterns: `op_Nil` is a variable that matches everything. - Selected lines that a SurroundsWith template places inside a string it opens are lexed as part of the snippet's own text, so a hole they open in an interpolated string no longer leaves the snippet's lines after the string unindented. - The nowarn snippet says in its description that it needs F# 10. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

github-project-automation Bot added this to F# Compiler and Tooling Sep 11, 2026

github-project-automation Bot moved this to New in F# Compiler and Tooling Sep 11, 2026

xperiandri marked this pull request as ready for review September 11, 2026 09:51

xperiandri requested a review from a team as a code owner September 11, 2026 09:51

xperiandri changed the title ~~Code snippets for F# in Visual Studio (Ctrl+K,Ctrl+X / Ctrl+K,Ctrl+S)~~ Code snippets for F# in Visual Studio (Ctrl+K,Ctrl+X / Ctrl+K,Ctrl+S) Sep 11, 2026

github-actions Bot added the ⚠️ Affects-Build-Infra Tooling check: PR touches build infrastructure label Sep 11, 2026

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github-actions Bot added ⚠️ Affects-Design-Time Tooling check: PR touches type providers or dependency manager ⚠️ Affects-Test-Tooling Tooling check: PR touches test framework infrastructure labels Sep 11, 2026

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github-project-automation Bot moved this from New to In Progress in F# Compiler and Tooling Sep 14, 2026

xperiandri changed the title ~~Code snippets for F# in Visual Studio (Ctrl+K,Ctrl+X / Ctrl+K,Ctrl+S)~~ Add F# code snippets (Ctrl+K,Ctrl+X / Ctrl+K,Ctrl+S) Sep 14, 2026

xperiandri force-pushed the feature/vs-code-snippets branch 2 times, most recently from 50be8a5 to 77bccb8 Compare September 17, 2026 22:51

xperiandri requested a review from T-Gro September 18, 2026 09:28

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T-Gro added the vsintegration-only Changes only Visual Studio integration, plus optional docs, release notes, or tests label Sep 21, 2026

xperiandri force-pushed the feature/vs-code-snippets branch from 2dacdf1 to 080f662 Compare September 21, 2026 17:56

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xperiandri and others added 9 commits October 10, 2026 23:39

Link the snippets release note to its issue and pull request

32ecdde

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Add a backgroundTask snippet

0f35134

Expands and surrounds like `task`, for code that has to run off the caller's context. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

xperiandri force-pushed the feature/vs-code-snippets branch from c282521 to c348baa Compare October 10, 2026 22:28

xperiandri and others added 2 commits October 11, 2026 01:30

Remove the duplicated release note

f8cc909

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Comment thread vsintegration/Vsix/VisualFSharpFull/snippets/1033/FSharp/nowarn.snippet

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