fix(extension): clamp Position character to avoid negative values#768
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Playwright reports error locations with column 0 when a stack frame has no column info (the fallback in playwright-core's stackTrace parser). The extension converted these via `column - 1`, producing -1, and VSCode's Position constructor throws "Illegal argument: character must be non-negative", surfacing as multiple uncaught errors on activation. Clamp `column - 1` the same way `line - 1` is already clamped, and update the Position mock to reject negatives so regressions are caught by the suite.
pavelfeldman
approved these changes
Apr 18, 2026
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Reference microsoft/playwright#40226
Summary
Users report the extension crashes with "Illegal argument: character must be non-negative" after a recent Windows update (25H2 / build 26200.8246), leaving no tests visible. The underlying trigger is a
connect ETIMEDOUT ::1:<port>when the extension fails to connect to its spawned Playwright test server (likely OS-level IPv6/loopback change). That's a separate root cause — this PR is about the crash that follows.When
listFiles()throws,TestModel._listFilessynthesizes a config error withlocation: { file: configFile, line: 0, column: 0 }. Downstream,TestTree._syncConfigErrors(andExtension._asPosition) didcolumn - 1without clamping — producingcharacter = -1, which VSCode'sPositionconstructor rejects. Six uncaught errors per activation, one per surfaced error location.column - 1the same wayline - 1was already clamped, at all three call sites that convert a Playwright error location into aPosition.Positionmock in tests to reject negative line/character (matching real VSCode behavior), so any future regression is caught by the suite.problems.spec.tscoveringcolumn = 0.The underlying ETIMEDOUT is not addressed here — this fix just keeps the extension usable (diagnostic is shown, tests remain discoverable) instead of crashing silently when it happens.