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[checks] Describe what the stream did in failures - #2811

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Oct 30, 2026
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[checks] Describe what the stream did in failures#2811
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@natebosch

@natebosch natebosch commented Oct 30, 2026

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Most StreamChecks rejections used a stream as the description of the
actual value, and put everything about what the stream did into the
which. a stream carries no information, and the line became more
visible once nested failures always include an Actual: line.

Follow the pattern of the Future expectations, where the actual describes
what the subject did, such as a future that completes as an error, and
the which describes how that fails the expectation:

  • emits on a closed stream: a stream that closed, which
    did not emit a value.
  • emitsError on a closed stream: a stream that closed, which
    did not emit an error.
  • emitsError on a value: a stream that emitted <v>, which
    emitted a value instead of an error.
  • emitsThrough: a stream that closed after emitting [...], which
    did not emit a matching value.
  • neverEmits: a stream that emitted [...], which
    emitted a matching value at index N: <v>.
  • isDone on a value: a stream that emitted <v>, which
    emitted a value before closing.
  • isDone on an error: a stream that emitted error <e>, which
    emitted an error before closing at: followed by the stack trace.

Errors use a stream that emitted error <e> in place of
a stream with error <e> for consistency.

emitsThrough and neverEmits now keep the values they consume so they
can list them instead of reporting a count. They keep only the first 25
values, along with the total count, so checking a long stream does not hold
on to every value. When there were more values the actual reads, for
example, a stream that emitted 30 values, starting with [...]. Since the
matching value may not be among those listed, neverEmits also repeats it
in its which.

inOrder and anyOf keep a stream, since each condition runs against its
own copy of the queue and there is no single history to describe. The
nested failures within them describe what the stream did.

This also fixes the which for emitsError when the stream emits a value,
which said closed without emitting an error.

@natebosch
[checks] Describe what the stream did in failures
449ed78 
Most `StreamChecks` rejections used `a stream` as the description of the
actual value, and put everything about what the stream did into the
`which`. `a stream` carries no information, and the line became more
visible once nested failures always include an `Actual:` line.

Follow the pattern of the `Future` expectations, where the actual describes
what the subject did, such as `a future that completes as an error`, and
the `which` describes how that fails the expectation:

- `emits` on a closed stream: `a stream that closed`, which
  `did not emit a value`.
- `emitsError` on a closed stream: `a stream that closed`, which
  `did not emit an error`.
- `emitsError` on a value: `a stream that emitted <v>`, which
  `emitted a value instead of an error`.
- `emitsThrough`: `a stream that closed after emitting [...]`, which
  `did not emit a matching value`.
- `neverEmits`: `a stream that emitted [...]`, which
  `emitted a matching value at index N: <v>`.
- `isDone` on a value: `a stream that emitted <v>`, which
  `emitted a value before closing`.
- `isDone` on an error: `a stream that emitted error <e>`, which
  `emitted an error before closing at:` followed by the stack trace.

Errors use `a stream that emitted error <e>` in place of
`a stream with error <e>` for consistency.

`emitsThrough` and `neverEmits` now keep the values they consume so they
can list them instead of reporting a count. They keep only the first 25
values, along with the total count, so checking a long stream does not hold
on to every value. When there were more values the actual reads, for
example, `a stream that emitted 30 values, starting with [...]`. Since the
matching value may not be among those listed, `neverEmits` also repeats it
in its `which`.

`inOrder` and `anyOf` keep `a stream`, since each condition runs against its
own copy of the queue and there is no single history to describe. The
nested failures within them describe what the stream did.

This also fixes the `which` for `emitsError` when the stream emits a value,
which said `closed without emitting an error`.
@natebosch
natebosch requested a review from a team as a code owner October 30, 2026 16:22
@github-actions github-actions Bot added the package:checks Issues related to pkg:checks label Oct 30, 2026
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github-actions Bot commented Oct 30, 2026

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

This check can be disabled by tagging the PR with skip-changelog-check (for example, for non-user-visible changes when the package version is already at -wip).

@natebosch natebosch mentioned this pull request Oct 30, 2026
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@brianquinlan
brianquinlan merged commit 10dc78c into master Oct 30, 2026
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@brianquinlan
brianquinlan deleted the stream-actuals branch October 30, 2026 18:21
@brianquinlan

brianquinlan commented Oct 30, 2026

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@natebosch I'm so sorry, I pressed the merge button in the wrong window! Hopefully that won't cause any issues.

@natebosch

natebosch commented Oct 30, 2026

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@natebosch I'm so sorry, I pressed the merge button in the wrong window! Hopefully that won't cause any issues.

No worries. The only thing I would have done differently is copy/paste the first comment into the commit message but having the PR link is sufficient to find that content so no real loss.

copybara-service Bot pushed a commit to dart-lang/sdk that referenced this pull request Nov 3, 2026
@natebosch dart-scoped@luci-project-accounts.iam.gserviceaccount.com
[deps] rev core, ecosystem, http, i18n, shelf, test, tools
c48ebb8 
Revisions updated by `dart tools/rev_sdk_deps.dart`.

core (https://github.com/dart-lang/core/compare/d7bd45c..24e09c4):
  24e09c4c  Sun Nov 1 21:12:19 2026 +0000  dependabot[bot]  Bump the github-actions group with 4 updates (dart-lang/core#1037)
  87ac1b4c  Fri Oct 30 16:02:43 2026 +0100  Michael Thomsen  [os_detect] Deprecate package:os_detect in favor of package:platform (dart-lang/core#1003)
  8debf335  Fri Oct 30 01:57:36 2026 +0530  Sahaja Pallapothula  Clarify Characters equality and Unicode normalization (dart-lang/core#1031)

ecosystem (https://github.com/dart-lang/ecosystem/compare/24b9ba8..f8faabf):
  f8faabf  Sun Nov 1 18:16:20 2026 +0000  dependabot[bot]  Bump the github-actions group with 2 updates (dart-lang/ecosystem#481)
  27c2fc8  Sat Oct 31 12:36:53 2026 +0100  Moritz  Fix publish workflow pins, add tag_prefix to health, and update docs (dart-lang/ecosystem#480)
  05641a9  Sat Oct 31 09:56:42 2026 +0100  Moritz  Restore deprecated publish.yaml workflow and firehose CLI entrypoint (dart-lang/ecosystem#479)
  78abf72  Fri Oct 30 08:24:07 2026 -0700  Kevin Moore  fix(repo_manage): use pub_semver for changelog -wip transitions (dart-lang/ecosystem#475)
  0bfa654  Fri Oct 30 09:33:57 2026 +0100  Moritz  Move publish check to health workflow and use individual package publishing workflows from `setup-dart` (dart-lang/ecosystem#454)
  adf7979  Thu Oct 29 23:46:49 2026 -0700  Kevin Moore  test(firehose): use hasLength, containsPair, and isFalse (dart-lang/ecosystem#477)

http (https://github.com/dart-lang/http/compare/c76dfb3..8c0d66a):
  8c0d66a  Fri Oct 30 09:54:41 2026 -0700  Brian Quinlan  chore(cupertino_http): check ffigen generation (dart-lang/http#2044)
  c8737d1  Fri Oct 30 09:11:46 2026 +0100  Moritz  chore(http): run Firefox tests with -headless instead of xvfb-run (dart-lang/http#2033)
  05d0b18  Fri Oct 30 07:08:19 2026 +0100  Moritz  fix(http2): make StreamException a StreamTransportException and forward ALPN errors to onError (dart-lang/http#2009)

i18n (https://github.com/dart-lang/i18n/compare/4c7b4ad..7475ce6):
  7475ce64  Sat Oct 31 02:49:28 2026 +0100  Moritz  [intl4x] Fix NumberFormat.percent ignoring digits (dart-lang/i18n#1115)

shelf (https://github.com/dart-lang/shelf/compare/62d3e4e..9946de5):
  9946de5  Sun Nov 1 12:27:59 2026 +0000  dependabot[bot]  build(deps): bump the github-actions group with 3 updates (dart-lang/shelf#554)

test (https://github.com/dart-lang/test/compare/6d74720..2a9e017):
  2a9e0175  Sun Nov 1 03:47:24 2026 +0000  dependabot[bot]  Bump the github-actions group with 6 updates (dart-lang/test#2813)
  55cd5cd5  Fri Oct 30 13:43:47 2026 -0700  Nate Bosch  Migrate publishing workflows from firehose to setup-dart (dart-lang/test#2812)
  10dc78c0  Fri Oct 30 11:21:53 2026 -0700  Nate Bosch  [checks] Describe what the stream did in failures (dart-lang/test#2811)
  c11ad06d  Fri Oct 30 08:59:57 2026 -0700  Nate Bosch  [checks] Add CheckFailure.describeNested (dart-lang/test#2793)
  0137b43e  Fri Oct 30 05:40:43 2026 +0530  Shriraj Jadhav  [checks] Use the Iterable.last member for the last expectation (dart-lang/test#2807)
  50c9f454  Thu Oct 29 15:11:39 2026 -0700  Nate Bosch  [checks] Collapse clauses for described conditions (dart-lang/test#2794)

tools (https://github.com/dart-lang/tools/compare/3980dca..1579f8d):
  1579f8d69  Mon Nov 2 02:44:58 2026 +0530  Joshua  fix(coverage): reject package: and dart: URIs outside known roots in Resolver (dart-lang/tools#2764)
  f869fdca4  Sun Nov 1 10:26:34 2026 +0100  dart-ecosystem-bot[bot]  [boring] Update BoringSSL to ed9209cf (dart-lang/tools#2774)
  d10e2b87f  Sun Nov 1 10:26:11 2026 +0100  dart-ecosystem-bot[bot]  [boring] Pin the prebuilt binaries of boring-binaries-20261101-33e9e69722af (dart-lang/tools#2777)
  33e9e6972  Sun Nov 1 05:56:30 2026 +0000  dependabot[bot]  build(deps): bump the github-actions group with 4 updates (dart-lang/tools#2775)
  f84d0d0d2  Sun Nov 1 05:36:12 2026 +0000  dependabot[bot]  build(deps): bump ffigen from 22.0.0 to 23.0.0 in /pkgs/boring (dart-lang/tools#2776)
  14ad5e515  Fri Oct 30 10:48:58 2026 -0700  Kevin Moore  [mime] Harden BoundMultipartStream error routing, headers, and epilogue (dart-lang/tools#2629)
  7a780d48c  Fri Oct 30 12:57:03 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid rescanning failed plain-text runs in InlineParser (dart-lang/tools#2757)
  3671d33a9  Fri Oct 30 12:56:48 2026 +0100  Jonas Finnemann Jensen  [markdown] Index footnote definitions and labels on Document for O(1) lookup (dart-lang/tools#2760)
  6f38e9fda  Fri Oct 30 12:56:09 2026 +0100  Jonas Finnemann Jensen  [markdown] Bound the domain of extended URL autolinks to DNS limits (dart-lang/tools#2759)
  aa0c38544  Fri Oct 30 12:20:40 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid quadratic removeRange in _combineAdjacentText (dart-lang/tools#2758)
  f425baf46  Fri Oct 30 11:16:28 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid rescanning failed space runs in LineBreakSyntax (dart-lang/tools#2756)
  c7eafbec3  Fri Oct 30 11:09:45 2026 +0100  Jonas Finnemann Jensen  [markdown] Reject '<' in AutolinkSyntax (dart-lang/tools#2755)
  86ed0f902  Fri Oct 30 11:08:25 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid quadratic backtracking in headerPattern (dart-lang/tools#2754)
  8ea07517f  Fri Oct 30 07:45:42 2026 +0100  Moritz  [boring] Regenerate the x509-limbo expected failures in the refresh job (dart-lang/tools#2712)
  40235c365  Thu Oct 29 14:46:17 2026 +0100  Jonas Finnemann Jensen  [markdown] Make HtmlBlockSyntax.parseChildLines iterative (dart-lang/tools#2749)
  0ff03f643  Thu Oct 29 14:41:33 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid re-escaping nested image alt text in ImageSyntax.createNode (dart-lang/tools#2752)
  784654d01  Thu Oct 29 14:37:11 2026 +0100  Jonas Finnemann Jensen  [markdown] Add test cases covering parser and renderer edge cases (dart-lang/tools#2753)
  4f2718ad8  Thu Oct 29 14:36:52 2026 +0100  Jonas Finnemann Jensen  [markdown] Make Document._parseInlineContent iterative (dart-lang/tools#2750)
  cac1421d5  Thu Oct 29 14:17:06 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid quadratic duplicate heading ID probing in HtmlRenderer (dart-lang/tools#2748)
  66880bcd3  Thu Oct 29 14:11:27 2026 +0100  Jonas Finnemann Jensen  [markdown] Check footnote label and empty map before scanning footnote keys (dart-lang/tools#2751)
  7f8696523  Thu Oct 29 14:07:06 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid quadratic blank-line lookahead in CodeBlockSyntax (dart-lang/tools#2747)
  9da6bb291  Thu Oct 29 14:03:04 2026 +0100  Jonas Finnemann Jensen  [markdown] Avoid exponential and quadratic backtracking in tablePattern (dart-lang/tools#2746)

dartdoc is held back at db94437, before dart-lang/dartdoc#4312, because its
mock SDK version changes conflict in the google3 3-way merge with the hotfix
in cl/1005963642.

native is held back at e0ca7c6, before dart-lang/native#3742, because
deprecating `MacOSCodeConfig(targetVersion: ...)` causes a fatal
`deprecated_member_use` diagnostic in `pkg/dartdev/lib/src/native_assets.dart`.

web is held back at 4e60e61, before dart-lang/web#596, because it changes
`package:web` signatures (e.g. `innerHTML=`, `parseFromString`, `Worker()`)
from `JSAny` to `String` in ways that break callers in google3.

Change-Id: I53d2cbde741c45b8fd33bca42742549819dd332b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/572780
Reviewed-by: Brian Quinlan <[email protected]>
Commit-Queue: Nate Bosch <[email protected]>
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