Fix formatter blank line and over-indent for union template argument by oha-4 · Pull Request #11010 · microsoft/typespec

oha-4 · 2026-06-17T12:21:28Z

Problem

When a union expression is used directly as one of multiple template arguments and the argument list is long enough to wrap, tsp format inserts a blank line before the union and indents its leading-| variants one level deeper than the sibling arguments:

model Picked
  is PickProperties<
    Sample,

      | "alpha"
      | "bravo"
      ...
  >;

Fix

printTemplateParameters already emits a softline + an indent level before each argument in a multi-argument list. printUnion was also emitting its own leading line + indent (+ align(2)), so the two stacked, producing the blank line and the extra indentation level.

printUnion now detects when the union is a direct argument of a multi-argument template reference (isInMultiTemplateArgumentList) and, in that case, lets the surrounding argument list control the line break and indentation. Result:

model Picked
  is PickProperties<
    Sample,
    | "alpha"
    | "bravo"
    ...
  >;

The standalone/value-position cases (e.g. alias X = "a" | "b" | ...) and the single-template-argument (shouldHug) case are unchanged, since there the surrounding context does not supply the line break/indent.

Tests

Added a regression test for the multi-argument case (Formatter adds a blank line and over-indents a union used as a template argument #11009) and a test pinning the single-argument behavior in formatter.test.ts.
Reformatted two committed http-client-java test fixtures that contained the buggy output (whitespace only; no semantic change).
pnpm prettier --check "**/*.tsp", formatter test suite, tsc, and eslint all pass.

When a `union` expression was used directly as one of multiple template arguments and the argument list wrapped, the formatter inserted a blank line before the union and indented its `|`-prefixed variants one level deeper than the sibling arguments. The argument list already supplies a line break and an indentation level before each argument, so `printUnion` no longer adds its own leading line and indent when the union is a direct argument of a multi-argument template reference. Fixes microsoft#11009 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

oha-4 · 2026-06-17T12:24:02Z

@microsoft-github-policy-service agree

pkg-pr-new · 2026-06-17T13:18:05Z

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/compiler@11010

commit: bd04975

github-actions · 2026-06-17T13:19:46Z

All changed packages have been documented.

✅ @typespec/compiler
✅ @typespec/http-client-java

Show changes

`@typespec/compiler` - fix ✏️

Fix formatter inserting a blank line and over-indenting a union expression used directly as one of multiple template arguments (e.g. PickProperties<Source, "a" | "b">)

`@typespec/http-client-java` - internal ✏️

Reformat union template arguments in test files to match updated formatter style.

timotheeguerin

Thanks for the contribution, I think there is also a regression this introduce in the formatting, i'll also need to see the effect this has on all of azure specs though it does seem like a good thing to fix

Address review feedback: the previous fix dropped align(2) on union variants when the union is a multi-argument template argument, which de-indented a nested template inside a variant. Keep align(2) unconditionally (matching prettier's union printer) so a breaking variant stays aligned under its "| " prefix, and add a regression test. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

oha-4 · 2026-06-17T14:26:06Z

Thanks for the careful review — you're right, fixed in 4daeb1b6b. The previous change dropped align(2) from the variants, which de-indented the nested template.

And to your question: this does follow prettier's union printer — indent-or-not depends on the parent (shouldIndent, union-type.js#L23-L38), but the per-variant align(2) is kept regardless (#L49-L56). I'd wrongly tied them together; now align(2) is unconditional, so a breaking variant stays aligned under its | , matching your screenshot. Added a regression test for it too.

Reformatting arm.tsp/response.tsp (union template arguments) changed the tcgc crossLanguageVersion hash of the generated metadata. Update the two *_metadata.json files to the regenerated hashes so the Java RegenCheck passes, and add an internal changeset for @typespec/http-client-java so the changelog check passes. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

A TemplateArgument node only ever exists as an element of TypeReference.arguments (the sole TemplateArgumentNode[] in the AST), so when the parent is a TemplateArgument the owning TypeReference is always the next node ancestor. Replace the variable-depth loop with a direct getParentNode(1) check; behavior is unchanged and all formatter tests pass. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

weidongxu-microsoft

approve on java lib to unblock.

but unsure why metadata file changes, they should not be affected by typespec source formatting. though I think Alan merged another unblocker.

timotheeguerin · 2026-06-22T13:36:40Z

approve on java lib to unblock.

but unsure why metadata file changes, they should not be affected by typespec source formatting. though I think Alan merged another unblocker.

yeah we investigated with Allen, I believe the issue is that the crossVersionId hashes the file content which the formatting affect. Should be good now

…osoft#11011) Fixes the `is`-breaking part of microsoft#11009 (the blank-line/over-indent part is addressed separately in microsoft#11010). ## Problem When a model/scalar heritage clause (`is X` / `extends X`) references a template with multiple arguments, the formatter wrapped the keyword and the template reference in a single `group(indent(...))`. Prettier measures that group against the full flat width of the template argument list, so the group broke and pushed the keyword onto its own indented line — even when the declaration line itself was short: ```tsp model Picked is PickProperties< Sample, ... >; ``` ## Fix `printHeritageClause` now keeps the keyword on the declaration line when the base is a template reference with multiple (breakable) arguments, and lets the template argument list control the line break: ```tsp model Picked is PickProperties< Sample, ... >; ``` Single-argument (hugged) and non-template bases keep the previous behavior of breaking the keyword onto its own line when the declaration is too long. ## Tests - Added regression tests for the multi-argument case on `model is`, `model extends`, and `scalar extends` in `formatter.test.ts`. - Reformatted one committed `http-client-java` test spec (`arm-customization.tsp`) that contained the old output (whitespace only, no semantic change). - Formatter test suite, eslint, tsc, and `prettier --check "**/*.tsp"` all pass locally. > Note: the `crossLanguageVersion` hash in the corresponding `*_metadata.json` is whitespace-sensitive; it will be updated from the RegenCheck output once CI runs. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

timotheeguerin · 2026-06-23T14:46:54Z

Thanks for the formatter fixes @oha-4

timotheeguerin · 2026-06-24T14:05:36Z

@oha-4 it seems like tests need to be updated as seems to conflict with your other pr I merged

…emplate-arg

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

…' into fix/formatter-union-template-arg

…oft#11093) Fixes microsoft#11092 ## Problem PR microsoft#11010 fixed a blank-line / over-indent issue when a `union` expression is used as one of several **positional** template arguments. That fix made `printUnion` suppress its own leading line + indent when the union is a direct argument of a multi-argument template reference (the surrounding argument list already supplies them). This regressed the **named** template argument case (`Name = <union>`). For a named argument the union is printed *after* `Name = `, so the argument list's line break / indent does **not** apply to the union variants. Suppressing the union's own break + indent collapsed the variants: ```tsp alias Alias = Test< A = "Some long value", TakesALongUnion = | string | int32 | int64 | "Some very long string that split line" >; ``` ## Fix `isInMultiTemplateArgumentList` now returns `false` when the parent `TemplateArgument` has a `name`. Named-argument unions fall back to the standalone behavior (their own leading `line` + `| ` + indent): ```tsp alias Alias = Test< A = "Some long value", TakesALongUnion = | string | int32 | int64 | "Some very long string that split line" >; ``` The single-argument case and the positional multi-argument case (microsoft#11009) are unchanged. ## Tests - Added a regression test for the named-union multi-argument case (microsoft#11092). - Existing microsoft#11009 positional tests still pass; full formatter suite (216 tests) passes. - `prettier --check "**/*.tsp"` clean; compiler builds.

oha-4 requested review from XiaofeiCao, anuchandy, bterlson, catalinaperalta, haolingdong-msft, iscai-msft, markcowl, srnagar, timotheeguerin, weidongxu-microsoft and witemple-msft as code owners June 17, 2026 12:21

microsoft-github-policy-service Bot added compiler:core Issues for @typespec/compiler emitter:client:java Issue for the Java client emitter: @typespec/http-client-java labels Jun 17, 2026

timotheeguerin reviewed Jun 17, 2026

View reviewed changes

Comment thread packages/http-client-java/generator/http-client-generator-test/tsp/arm.tsp Outdated

oha-4 requested a review from timotheeguerin June 17, 2026 15:37

oha-4 mentioned this pull request Jun 17, 2026

Keep is/extends inline for multi-argument template heritage #11011

Merged

timotheeguerin reviewed Jun 18, 2026

View reviewed changes

Comment thread packages/compiler/src/formatter/print/printer.ts Outdated

weidongxu-microsoft reviewed Jun 22, 2026

View reviewed changes

weidongxu-microsoft approved these changes Jun 22, 2026

View reviewed changes

Merge branch 'main' into fix/formatter-union-template-arg

6e0d095

oha-4 requested a review from alzimmermsft as a code owner June 22, 2026 05:24

timotheeguerin approved these changes Jun 23, 2026

View reviewed changes

timotheeguerin added this pull request to the merge queue Jun 23, 2026

github-merge-queue Bot removed this pull request from the merge queue due to failed status checks Jun 23, 2026

Merge branch 'main' into fix/formatter-union-template-arg

936dd70

oha-4 and others added 3 commits June 24, 2026 23:12

Merge remote-tracking branch 'origin/main' into fix/formatter-union-t…

ea19def

…emplate-arg

Update union template arg formatter tests for inline heritage merge

c46c300

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Merge remote-tracking branch 'origin/fix/formatter-union-template-arg…

bd04975

…' into fix/formatter-union-template-arg

timotheeguerin enabled auto-merge June 24, 2026 15:13

timotheeguerin approved these changes Jun 24, 2026

View reviewed changes

timotheeguerin added this pull request to the merge queue Jun 24, 2026

Merged via the queue into microsoft:main with commit 482035c Jun 24, 2026
39 checks passed

oha-4 deleted the fix/formatter-union-template-arg branch June 24, 2026 17:49

This was referenced Jun 25, 2026

Regression in formatting #11092

Closed

Fix formatter regression for union as named template argument #11093

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Fix formatter blank line and over-indent for union template argument#11010

Fix formatter blank line and over-indent for union template argument#11010
timotheeguerin merged 9 commits into
microsoft:mainfrom
oha-4:fix/formatter-union-template-arg

oha-4 commented Jun 17, 2026

Uh oh!

oha-4 commented Jun 17, 2026

Uh oh!

pkg-pr-new Bot commented Jun 17, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Jun 17, 2026 •

edited

Loading

`@typespec/compiler` - fix ✏️

`@typespec/http-client-java` - internal ✏️

Uh oh!

timotheeguerin left a comment •

edited

Loading

Uh oh!

Uh oh!

oha-4 commented Jun 17, 2026

Uh oh!

Uh oh!

weidongxu-microsoft left a comment •

edited

Loading

Uh oh!

timotheeguerin commented Jun 22, 2026

Uh oh!

timotheeguerin commented Jun 23, 2026

Uh oh!

Uh oh!

timotheeguerin commented Jun 24, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Uh oh!

Conversation

oha-4 commented Jun 17, 2026

Problem

Fix

Tests

Uh oh!

oha-4 commented Jun 17, 2026

Uh oh!

pkg-pr-new Bot commented Jun 17, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot commented Jun 17, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

@typespec/compiler - fix ✏️

@typespec/http-client-java - internal ✏️

Uh oh!

timotheeguerin left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

oha-4 commented Jun 17, 2026

Uh oh!

Uh oh!

weidongxu-microsoft left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

timotheeguerin commented Jun 22, 2026

Uh oh!

timotheeguerin commented Jun 23, 2026

Uh oh!

Uh oh!

timotheeguerin commented Jun 24, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

pkg-pr-new Bot commented Jun 17, 2026 •

edited

Loading

github-actions Bot commented Jun 17, 2026 •

edited

Loading

`@typespec/compiler` - fix ✏️

`@typespec/http-client-java` - internal ✏️

timotheeguerin left a comment •

edited

Loading

weidongxu-microsoft left a comment •

edited

Loading