[tool_crash] Unhandled RangeError in CompactReporter._progressLine / truncate when terminal width is narrow #194569

Summary

flutter test crashes with an unhandled RangeError in truncate (package:test_core/src/util/pretty_print.dart:65) called from CompactReporter._progressLine (package:test_core/src/runner/reporter/compact.dart:445) when stdout.terminalColumns (lineLength) is narrow enough that lineLength - length < 4.

Crash Telemetry (Flutter stable/3.47.7)

• Signature: RangeError at RangeError.checkValidRange at dart:core/errors.dart-aa4dd664
• Rank: Tweak to use async/await #2 Top Crasher in 3.47.7
• Total Occurrences: 79 (15.3% of Top 10, 8.0% of all 3.47.7 crashes, ~10.3 crashes/day)
• Platform Distribution: Windows: 77 (97.5%), macOS: 2 (2.5%)
• Sample Command: flutter test test/app_state_test.dart --plain-name AppState Model and Discovery State Tests 3. Clearing search restores the correct filtered results
• Error:

RangeError (start): Invalid value: Not in inclusive range 0..81: 84

Stack Trace

#0      RangeError.checkValidRange (dart:core/errors.dart:387)
#1      _StringBase.substring (dart:core-patch/string_patch.dart:437)
#2      truncate (package:test_core/src/util/pretty_print.dart:65)
#3      CompactReporter._progressLine (package:test_core/src/runner/reporter/compact.dart:445)
#4      CompactReporter._onTestStarted (package:test_core/src/runner/reporter/compact.dart:216)
#5      _rootRunUnary (dart:async/zone_root.dart:56)
#6      _CustomZone.runUnary (dart:async/zone.dart:816)
#7      _CustomZone.runUnaryGuarded (dart:async/zone.dart:710)

Root Cause

In CompactReporter._progressLine (package:test_core/src/runner/reporter/compact.dart:444-450), the reporter computes the visible prefix length var length = withoutColors(buffer.toString()).length (e.g. 11 characters for \r00:00 +0: ) and calls utils.truncate(message, lineLength - length) followed by ' ' * (lineLength - withoutColors(buffer.toString()).length). When stdout.terminalColumns (lineLength in package:test_core/src/util/io.dart:27-37) reports a narrow column width on Windows ConPTY or narrow IDE terminal panes such that maxLength = lineLength - length < 4 (for example, lineLength == 12 and length == 11, giving maxLength == 1), truncate (package:test_core/src/util/pretty_print.dart:65) computes text.substring(text.length - maxLength + 4) (81 - 1 + 4 = 84), throwing a RangeError because the start index exceeds text.length (81).

Recommendation

1. In truncate (package:test_core/src/util/pretty_print.dart), guard against maxLength <= 4 (e.g., return '' when maxLength <= 0 and '.' * maxLength when maxLength <= 3, or clamp the substring start index to 0..text.length).
2. In CompactReporter._progressLine (package:test_core/src/runner/reporter/compact.dart), clamp lineLength - length to a non-negative value before calling utils.truncate and before repeating ' '.
3. In lineLength (package:test_core/src/util/io.dart), fall back to _defaultLineLength (or a reasonable minimum width) when stdout.terminalColumns returns an abnormally small value.