TypeError: path.charCodeAt is not a function

Bug Report

When creating a simple plugin that proxies LanguageService methods (see https://github.com/Microsoft/TypeScript/wiki/Writing-a-Language-Service-Plugin), I see new errors in the log when opening files in VSCode:

Err 3697  [16:56:41.128] Exception on executing command delayed processing of request 9:

    path.charCodeAt is not a function

    TypeError: path.charCodeAt is not a function
        at getEncodedRootLength
        at isRootedDiskPath
        at Object.toPath
        at toPath
        at Object.getSourceFile
        at getValidSourceFile
        at Object.getSyntacticDiagnostics
        at wrapLanguageServiceMethodInResult
        at Object.proxy.<computed> [as getSyntacticDiagnostics]
        at IOSession.Session.syntacticCheck
        at checkOne
        at MultistepOperation.executeAction
        at 
        at IOSession.Session.executeWithRequestId
        at Object.executeWithRequestId
        at Timeout._onTimeout
        at listOnTimeout
        at processTimers

It repros reliably for some files but does not repro for other files.

After debugging I found that the path variable passed to getEncodedRoothLength is not a string as expected, but rather a string array with one string.

🔎 Search Terms

TypeError: path.charCodeAt is not a function

🕗 Version & Regression Information

  • I was unable to test this on prior versions because my project is hard to change TS versions on and I do not have a simple reliable repro.

Playground Link

💻 Code

🙁 Actual behavior

Type error that breaks diagnostics

🙂 Expected behavior

No error

1 thought on “TypeError: path.charCodeAt is not a function

  1. This was a bug in my plugin. If you see an error like this, check to see if variadic arguments are being forward properly in the plugin you install.

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