util: honor breakLength: Infinity for deep objects and arrays

[RohithPariki]

Problem

When using util.inspect(obj, { breakLength: Infinity }), the output is expected to always be formatted as a single line, as per the Node.js documentation. However, deeply nested objects and arrays with many items are incorrectly split across multiple lines if they trigger the compact depth limit or array column grouping.

Root Cause

Two separate heuristics in lib/internal/util/inspect.js were ignoring the breakLength === Infinity condition:

1. reduceToSingleString(): Enforces line breaks if ctx.currentDepth - recurseTimes >= ctx.compact.
2. groupArrayElements(): Splits arrays with more than 6 items into multiple columns of up to 15 items, causing newlines.

Solution

1. In groupArrayElements, explicitly return early when ctx.breakLength === Infinity, preventing any column grouping.
2. In reduceToSingleString, allow inline consolidation to bypass the depth check if ctx.breakLength === Infinity.

This guarantees that all elements (objects and arrays alike) are strictly formatted on a single line when breakLength is Infinity, fixing the bug correctly without edge case holes.

Testing

• Updated regression tests in test/parallel/test-util-inspect.js.
• Added tests for deep arrays and objects with depth: Infinity and finite depths to ensure they always render as a single line when breakLength: Infinity.

Fixes: #60475

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.43%. Comparing base (617e082) to head (5cf8250).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #66471   +/-   ##
=======================================
  Coverage   90.42%   90.43%           
=======================================
  Files         790      790           
  Lines      275435   275439    +4     
  Branches    52826    52822    -4     
=======================================
+ Hits       249070   249085   +15     
- Misses      16765    16768    +3     
+ Partials     9600     9586   -14     

Files with missing lines	Coverage Δ
lib/internal/util/inspect.js	97.04% <100.00%> (+<0.01%)	⬆️

... and 25 files with indirect coverage changes

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[RohithPariki]

Reworked the implementation around the underlying issue. The previous implementation has been replaced with a focused solution that properly handles arrays (disabling column grouping) and deep objects (bypassing compact depth constraints) when breakLength: Infinity is passed, which was previously failing for finite depths and large arrays. The commit message was also reformatted to pass the linter. The PR description has been updated to reflect the new implementation.

[RohithPariki]

I've fixed the test failure! It turned out that the test for the object structure was still expecting some nested newlines, which �reakLength: Infinity properly eliminates. The expected output is now correctly formatted as a single line inline string. The CI should pass now.

[MikeMcC399]

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