Add --coverage-path and --branch-coverage options

[liamappelbe]

• Add a --coverage-path option to dart test, which takes a filename. This option works like --coverage, except that instead of generating multiple JSON reports, it generates a single LCOV report.
  • Aside from plumbing, the main change is in pkgs/test_core/lib/src/runner/coverage.dart's coverage collection functions, and how pkgs/test_core/lib/src/runner/engine.dart invokes them.
  • In LCOV mode, writeCoverage is still called, but doesn't write the JSON file. Instead it returns the generated coverage report. The Engine merges all these coverage reports into _allCoverageData, and once all the tests are done it calls writeCoverageLcov to finalize the report and write it to the lcov file.
• Add a --branch-coverage flag that is plumbed through to collect's branchCoverage param.
• Update the README to mention the --coverage-path workflow.
• Set collect's scopedOutput param to the current package name. This front load the filtering of the coverage report, improving performance by removing unnecessary information as early as possible.
• The test util runPub was using the deprecated standalone pub tool. This didn't cause problems because it was dead code. But I had to use it in the new tests, so I updated it to use dart pub.

Fixes #2511

[github-actions]

PR Health

Changelog Entry ✔️

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Changes to files need to be accounted for in their respective changelogs.

[liamappelbe]

The remaining test failures don't seem related to this PR

[liamappelbe]

This is ready for review. @jakemac53 @natebosch PTAL.

[liamappelbe]

@jakemac53 @natebosch Friendly ping

[jakemac53]

Just FYI I am no longer officially on this project and don't have time to do reviews at the moment 😭 .

[natebosch]

I think if we rename --coverage-lcov to --coverage-path as mentioned on the issue we'll be pretty well set up to normalize things in the future. It's a bit less obvious in the mean time, but I think it'll be a better place to end up long term.

[natebosch]

This may need some attention before we can publish it. The dependency on package:coverage from lib/src/runner/coverage.dart causes a cycle in the targets split out for blaze.

[liamappelbe]

This may need some attention before we can publish it. The dependency on package:coverage from lib/src/runner/coverage.dart causes a cycle in the targets split out for blaze.

Can you give some more details? package:coverage doesn't depend on package:test afaik (aside from a dev dep)

[natebosch]

Ah sorry I should have updated this issue - after I dug further I found it wasn't a cycle and we just needed a tweak in the build targets to fix the config around a conditional import. No worries here - I have the roll to google3 working.

[alexmarkov]

It looks like this PR broke Flutter build (after package:test was rolled to Dart SDK):

[10037/10156] ACTION //flutter/testing/dart:compile_assets_test.dart(//build/toolchain/linux:clang_x64)
FAILED: gen/assets_test.dart.dill 
vpython3 ../../flutter/third_party/dart/build/gn_run_binary.py compiled_action ../../flutter/third_party/dart/tools/sdks/dart-sdk/bin/dart --dfe=../../flutter/third_party/dart/tools/sdks/dart-sdk/bin/snapshots/kernel-service.dart.snapshot ../../flutter/third_party/dart/pkg/frontend_server/bin/frontend_server_starter.dart -DkFlutterSrcDirectory=/b/s/w/ir/cache/builder/flutter/engine/src/flutter -DkFlutterBuildDirectory=/b/s/w/ir/cache/builder/flutter/engine/src/out/host_debug_unopt/gen -DkSkiaGoldWorkDirectory=/b/s/w/ir/cache/builder/flutter/engine/src/out/host_debug_unopt/gen/skia_gold_assets_test.dart --packages /b/s/w/ir/cache/builder/flutter/engine/src/flutter/.dart_tool/package_config.json --sdk-root flutter_patched_sdk --target=flutter --depfile gen/assets_test.dart.dill.d --output-dill gen/assets_test.dart.dill ../../flutter/testing/dart/assets_test.dart
Command failed: /b/s/w/ir/cache/builder/flutter/engine/src/flutter/third_party/dart/tools/sdks/dart-sdk/bin/dart --dfe=../../flutter/third_party/dart/tools/sdks/dart-sdk/bin/snapshots/kernel-service.dart.snapshot ../../flutter/third_party/dart/pkg/frontend_server/bin/frontend_server_starter.dart -DkFlutterSrcDirectory=/b/s/w/ir/cache/builder/flutter/engine/src/flutter -DkFlutterBuildDirectory=/b/s/w/ir/cache/builder/flutter/engine/src/out/host_debug_unopt/gen -DkSkiaGoldWorkDirectory=/b/s/w/ir/cache/builder/flutter/engine/src/out/host_debug_unopt/gen/skia_gold_assets_test.dart --packages /b/s/w/ir/cache/builder/flutter/engine/src/flutter/.dart_tool/package_config.json --sdk-root flutter_patched_sdk --target=flutter --depfile gen/assets_test.dart.dill.d --output-dill gen/assets_test.dart.dill ../../flutter/testing/dart/assets_test.dart
exitCode: 254
output: result 22932273-0a39-494a-9f33-4d23e514ffc2
../../flutter/third_party/dart/third_party/pkg/test/pkgs/test_core/lib/src/runner/coverage.dart:43:48: Error: The method 'filterIgnored' isn't defined for the type 'Map<String, HitMap>'.
 - 'Map' is from 'dart:core'.
 - 'HitMap' is from 'package:coverage/src/hitmap.dart' ('../../flutter/third_party/pkg/coverage/lib/src/hitmap.dart').
Try correcting the name to the name of an existing method, or defining a method named 'filterIgnored'.
  final filteredCoverageData = allCoverageData.filterIgnored(

full log

[DanTup]

@liamappelbe pkg:test in the SDK has been updated now (since @alexmarkov's comment above, it re-landed in 277c4a1f50826c8bab1bdbd73ea586f3cba8c8a0 and has rolled into Flutter successfully).

However, when using a bleeding-edge build based on 44207f801bafa97152a722bc794a22d67719a7e5 I get errors that --coverage-path is not valid:

PS D:\Dev\Test Projects\dartcode_5693> dart --version
Dart SDK version: 3.10.0-edge.44207f801bafa97152a722bc794a22d67719a7e5 (main) (Mon Sep 15 06:20:22 2025 -0700) on "windows_x64"


PS D:\Dev\Test Projects\dartcode_5693> dart test --coverage-path x.y .\test\foo5_test.dart
Could not find an option named "--coverage-path".

Usage: dart test [files or directories...]

-h, --help                            Show this usage information.
    --version                         Show the package:test version.

My first thought was that the dart test command in pkg:dartdev was doing its own parsing of args, but I see it's using ArgParser.allowAnything(). Any ideas why this might not work?

[DanTup]

Oh, never mind - this is because it depends on the version of pkg:test my project is using, not what was in the SDK. I'll test it using a git dependency, and wait for a new pkg:test release before shipping anything. Thanks!