[FR]: Making `EXPECT_THAT` of `(Unordered)ElementsAreArray` human/AI readable

[kenoss]

Does the feature exist in the most recent commit?

I guess yes (version that is used in chromium).

Why do we need this feature?

For daily chromium development.

Describe the proposal.

Motivation

I think that the current output of EXPECT_THAT of (Unordered)ElementsAreArray is not human/AI readable. We can improve it.

Example

Code: Something like https://source.chromium.org/chromium/chromium/src/+/main:content/browser/preloading/prerender/prerender_browsertest.cc;l=8357;drc=02e3f72738b5ad02e8f30ab40ea1467550a91f2c

Result:

../../content/browser/preloading/prerender/prerender_browsertest.cc:8988: Failure
Value of: prerender_entries
Expected: has 4 elements where
element #0 is equal to Entry{source=65 AccurateTriggering=1 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=5 },
element #1 is equal to Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=4 },
element #2 is equal to Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=186 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=6 },
element #3 is equal to Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 }
  Actual: { Entry{source=65 AccurateTriggering=1 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=5 }, Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 }, Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=9 }, Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=9 } }, whose element #1 (Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 }) isn't equal to Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=4 }

It's not readable for me. What I'm currently doing is:

1. Find "whose element ASSERT_STRCASEEQ and ASSERT_STRCASENE macros should compare strings consistently across platforms #1".
2. Copy the line.
3. Paste to an editor.
4. Edit
5. Eye diff

Editted result:

whose element #1 (
Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 }
) isn't equal to 
Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=4 }

Then, I got Diff: prerender_entries[1], ReadyTime=1247, TriggeringOutcome=3/4.

Sometimes I ask to an AI to visualize the diff.

This work is in most-inner loop of iteration. It's OK for oneshot, but I need to do it for every edit and compile.

Possible solutions

I prefer

• Human/AI readable output.
• Structural output rather than natural english.

Imporved output:

../../content/browser/preloading/prerender/prerender_browsertest.cc:8988: Failure
Value of: prerender_entries
Expected: With `ElementsAreArray`
  - Entry{source=65 AccurateTriggering=1 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=5 },
  - Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=4 },
  - Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=186 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=6 },
  - Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 }
Actual:
  - Entry{source=65 AccurateTriggering=1 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=5 },
  - Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 },
  - Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=9 },
  - Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=9 } }
Note that the expected element #1 isn't equal to the actual one.
  - Expected #1: Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=3 }
  - Actual   #1: Entry{source=65 AccurateTriggering=0 Eligibility=1 FailureReason=0 HoldbackStatus=1 PreloadingPredictor=50 PreloadingType=4 ReadyTime=1247 SpeculationEagerness=2 TimeToNextNavigation=1247 TriggeringOutcome=4 }

Points:

1. Comparison using LHS/RHS.
2. Same indentation and format for LHS/RHS.
3. Say the conclusion first and avoid embedding parameters. (Note that the expected element #1 isn'st equal to the actual one.\n - {lhs}\n - {rhs} rather than Actual {actual}, whose element #1 ({rhs}) isn't equal to {lhs}. Note also that the natural English version reverts the order as actual/expected, which is avoided in gtest.)

WDYT?

Is the feature specific to an operating system, compiler, or build system version?

No.

[ShrutiPundir17]

Implemented improved mismatch explanations for ElementsAreArray and UnorderedElementsAreArray to make debugging output more readable and structured.

Would appreciate feedback and review. Thanks!

[kenoss]

Looks great! Thank you for your contribution!

I'll delegate a review to the owners as I'm not a maintainer.

[ShrutiPundir17]

Looks great! Thank you for your contribution!

I'll delegate a review to the owners as I'm not a maintainer.

Hi kenoss
Any update on review?