lib,test_runner: fix styleText colorizing non-TTY streams under --test

[piyushrajyadav]

Summary

Fixes: #57921
Refs: #57935 (previous attempt, closed stale)

Problem

When
ode --test runs files in process-isolation mode it sets FORCE_COLOR=1 in the child's environment to carry test-reporter colour through. A side-effect is that util.styleText() in user code inside the child colorises any stream — even those with isTTY = false — because shouldColorize() short-circuits to getColorDepth() as soon as FORCE_COLOR is defined, ignoring the caller's stream entirely.

js // With node --test, FORCE_COLOR=1 is injected into the child env. // Both of these then return ANSI-styled text, even though streamNoTTY.isTTY = false: styleText('bgYellow', 'TTY', { stream: streamTTY }); // ← correct styleText('bgYellow', 'No TTY', { stream: streamNoTTY }); // ← WRONG (bug)

Approach

Previous PR #57935 explored a few directions. cjihrig suggested not hacking FORCE_COLOR at all and using NODE_TEST_CONTEXT (the existing test-runner-internal env var) as a communication channel instead.

This PR implements exactly that:

lib/internal/test_runner/runner.js

• Remove env.FORCE_COLOR = '1'
• Add NODE_TEST_CONTEXT as a JSON string: { context: 'child-v8', colorize: }

lib/internal/util/colors.js — shouldColorize() priority order

1. FORCE_COLOR — user-controlled, unchanged, highest priority
2. stream.isTTY — stream capability check, unchanged
3. NODE_TEST_CONTEXT.colorize — new last-resort fallback, only used when neither of the above is truthy

js shouldColorize(stream) { if (process.env.FORCE_COLOR !== undefined) { return lazyInternalTTY().getColorDepth() > 2; } if (stream?.isTTY) { return typeof stream.getColorDepth === 'function' ? stream.getColorDepth() > 2 : true; } // Last resort: test-runner internal colorize flag const ctx = getTestContext(); return ctx?.colorize === true && lazyInternalTTY().getColorDepth() > 2; },

lib/internal/test_runner/utils.js

• Updated isChildProcessV8 detection to handle both the legacy plain-string 'child-v8' and the new JSON { context: 'child-v8' } forms.

Testing

• Existing test cases in est/parallel/test-util-styletext.js retained
• Added regression cases exercising NODE_TEST_CONTEXT.colorize for isTTY=false streams