💬 ชาวเน็ตแห่แชร์: Kotlin/ktfmt/pull/

ZacSweers · 2026-04-28T20:37:31Z

This is a continuation of #574 with the updated option control to orient around the requested --preserve-lambda-breaks simple option. With this, lambda block line breaks are simply just respected rather than have ktfmt impose anything.

Aside from finishing up the previous PR, this also adds a setting to the IJ plugin.

I cherrypicked the original commits to preserve authorship history (CC @loganj)

Resolves #547

Edit

After chatting on slack I updated the PR with a couple things:

Added a builder API for CLI tools to use in the future to avoid ABI breakages
Flipped the semantics to enable this by default, but can revert if you want to keep the old setup. I do think enabled by default is good

ZacSweers · 2026-04-28T20:47:36Z

The CI failure looks like a bootstrap compatibility issue - can't add a new param without breaking ktfmt-gradle since it's statically compiled against the only one? I tried adding @JvmOverloads to the constructor but no dice on that either, it's a chicken-and-egg problem 😅 🥚

hick209

Love the work you did here! Thank you so much and sorry it took so long to get to this.

I am not fully confident on exposing this via CLI flag yet, everything else LGTM.
Regardless I'll pull it internally for review.

meta-codesync · 2026-05-19T12:58:18Z

@hick209 has imported this pull request. If you are a Meta employee, you can view this in D105690093.

hick209

Oh, please do not forget to update the CHANGELOG.md

ZacSweers · 2026-05-19T15:22:58Z

Updated the changelog and added another constructor overload. For the latter - it may be valuable before 1.0.0 to expose a Builder API for this to avoid the churn for tools programmatically calling this

ZacSweers · 2026-05-19T15:28:35Z

Doesn't look like we can get away with an overload

Execution failed for task ':ktfmt:ktfmtFormatMain'.
> There were multiple failures while executing work items
   > A failure occurred while executing com.ncorti.ktfmt.gradle.tasks.worker.KtfmtWorkAction
      > 'void com.facebook.ktfmt.format.FormattingOptions.<init>(int, int, int, com.facebook.ktfmt.format.TrailingCommaManagementStrategy, boolean, boolean)'
   > A failure occurred while executing com.ncorti.ktfmt.gradle.tasks.worker.KtfmtWorkAction
      > 'void com.facebook.ktfmt.format.FormattingOptions.<init>(int, int, int, com.facebook.ktfmt.format.TrailingCommaManagementStrategy, boolean, boolean)'
   > A failure occurred while executing com.ncorti.ktfmt.gradle.tasks.worker.KtfmtWorkAction
      > 'void com.facebook.ktfmt.format.FormattingOptions.<init>(int, int, int, com.facebook.ktfmt.format.TrailingCommaManagementStrategy, boolean, boolean)'
   > A failure occurred while executing com.ncorti.ktfmt.gradle.tasks.worker.KtfmtWorkAction
      > 'void com.facebook.ktfmt.format.FormattingOptions.<init>(int, int, int, com.facebook.ktfmt.format.TrailingCommaManagementStrategy, boolean, boolean)'
   > A failure occurred while executing com.ncorti.ktfmt.gradle.tasks.worker.KtfmtWorkAction
      > 'void com.facebook.ktfmt.format.FormattingOptions.<init>(int, int, int, com.facebook.ktfmt.format.TrailingCommaManagementStrategy, boolean, boolean)'
   > A failure occurred while executing com.ncorti.ktfmt.gradle.tasks.worker.KtfmtWorkAction
      > 'void com.facebook.ktfmt.format.FormattingOptions.<init>(int, int, int, com.facebook.ktfmt.format.TrailingCommaManagementStrategy, boolean, boolean)'

hick209 · 2026-05-19T16:00:11Z

Debugged offline via Slack

Add new boolean configuration option to FormattingOptions and wire it through the command-line interface. This option will enable cascading lambda break decisions to nested trailing lambdas, useful for DSLs like Jetpack Compose. Changes: - Add cascadeNestedLambdaBreaks field to FormattingOptions data class - Add --cascade-nested-lambda-breaks command-line flag to ParsedArgs - Update CLI help text to document the new option - Default value is false to maintain backward compatibility 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

Add parentLambdaBroke parameter to track parent lambda break state through nested lambda expressions. Add helper method to identify trailing lambdas that should inherit hierarchy preservation. Changes: - Add parentLambdaBroke parameter to visitLambdaExpressionInternal - Add isTrailingLambda helper method to detect trailing lambdas - Update method documentation to explain new parameter - All call sites use default value (false) for now No functional changes yet - context is passed but not used. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

Implement the core cascading lambda break functionality. When cascadeNestedLambdaBreaks is enabled and a parent lambda breaks to multi-line, all nested trailing lambdas are forced to break as well, preserving visual hierarchy. Changes: - Add insideBreakingLambda member variable to track break state - Detect when current lambda will break to multi-line - Force nested trailing lambdas to multi-line when parent broke - Propagate break state through nested lambda visitor calls - Update visitArgumentInternal and visitLambdaOrScopingFunction The feature is now functional when --cascade-nested-lambda-breaks flag is enabled. Backward compatible - default behavior unchanged. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

Add 7 comprehensive test cases covering various scenarios for the cascadeNestedLambdaBreaks feature. Tests verify basic hierarchy preservation, backward compatibility, deep nesting, edge cases, and that only trailing lambdas are affected. Changes: - Add test for forcing nested lambda hierarchy when option enabled - Add test for maintaining single line when option disabled - Add test for forcing only trailing lambdas (not map/filter) - Add test for forcing behavior when parent breaks - Add test for preserving hierarchy with multiple statements - Add test for handling deep nesting levels - Add test for no effect on non-nested lambdas - Fix containsTrailingLambdas to correctly detect nested lambdas - Update break detection logic to handle hierarchy properly All tests pass, feature fully functional. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

Document the new --cascade-nested-lambda-breaks command-line option in the README with examples and usage guidelines. The documentation explains how the feature helps preserve visual hierarchy in DSL code like Jetpack Compose. Changes: - Add "Cascading Lambda Breaks" section to README.md - Include usage examples showing before/after formatting - Clarify that option only affects trailing lambdas - Note that it's useful for DSLs with semantic nesting Feature is now fully implemented, tested, and documented. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>

meta-codesync · 2026-05-25T18:31:26Z

@hick209 merged this pull request in f70155a.

meta-cla Bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Apr 28, 2026

hick209 reviewed May 19, 2026

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Comment thread core/src/main/java/com/facebook/ktfmt/format/FormattingOptions.kt Outdated

hick209 requested changes May 19, 2026

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loganj and others added 13 commits May 19, 2026 18:01

Rework to --preserve-lambda-breaks option

702b00b

Update tests

9e8b320

Exclude .kotlin/ dir for k2 sessions

520c51d

Add an IJ setting

6292529

Update README

09e3435

CHANGELOG

58c81c4

Another backward compat

2bb29b6

Formatting

c7a7e58

ZacSweers force-pushed the z/cascadingDslLambdas branch from 4418c9d to c7a7e58 Compare May 19, 2026 16:02

hick209 approved these changes May 19, 2026

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ZacSweers added 4 commits May 19, 2026 18:07

Update API

e67c773

Add a builder

17250ae

Add an extra test for partial formatting

d0e90e1

Flip semantics to enabled by default

fe90916

ZacSweers changed the title ~~Add --preserve-lambda-breaks option~~ Default to preserving lambda line breaks May 23, 2026

hick209 requested changes May 24, 2026

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Comment thread core/src/main/java/com/facebook/ktfmt/cli/ParsedArgs.kt Outdated

Remove CLI arg

3c5f5fd

hick209 approved these changes May 25, 2026

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meta-codesync Bot closed this in f70155a May 25, 2026

facebook-github-tools Bot added the Merged label May 25, 2026

hick209 mentioned this pull request May 26, 2026

One line lambdas in .kts files #181

Closed

artnc mentioned this pull request May 27, 2026

Update ktfmt to 0.63 duolingo/pre-commit-hooks#85

Merged

Goooler mentioned this pull request Jun 2, 2026

Migrate from Ktlint to Ktfmt tunjid/heron#1003

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Default to preserving lambda line breaks - #614

Default to preserving lambda line breaks#614
ZacSweers wants to merge 18 commits into
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ZacSweers commented Apr 28, 2026 •

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