• Benedikt Meurer's avatar
    [console] Proper type conversions in console builtins. · 099cb420
    Benedikt Meurer authored
    This updates the following set of console builtins in V8 to match the
    Console Standard (https://console.spec.whatwg.org) with respect to
    (potentially side effecting) type conversions:
    
      - console.debug
      - console.error
      - console.info
      - console.log
      - console.trace
      - console.warn
      - console.group
      - console.groupCollapsed
      - console.assert
    
    The V8 implementation only performs the type conversions and updates
    the arguments in-place with the results from the %String% constructor,
    %parseInt%, or %parseFloat% invocations. The actual formatting is
    still left completely to the debugger front-end.
    
    To give a concrete example, the following code
    
    ```js
    const msgFmt = {
      toString() { return 'Message %i' }
    };
    console.log('LOG: %s`, msgFmt, 42);
    ```
    
    sends the following parameters to the debugger front-end
    
    ```js
    ["LOG: %s", "Message %i", 42]
    ```
    
    and it's then the job of the front-end to perform the actual string
    substitutions.
    
    It's also worth calling out that the console builtins are only
    concerned with %s, %f, %d, and %i formatting specifiers, since
    these are the only ones that trigger type conversions, and %o, %O,
    and %c can only be implemented in a meaningful way at a higher
    level.
    
    Fixed: chromium:1277944
    Bug: chromium:1282076
    Doc: https://bit.ly/v8-proper-console-type-conversions
    Spec: https://console.spec.whatwg.org
    Change-Id: I0996680811aa96236bd0d879e4a11101629ef1a7
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3352118Reviewed-by: 's avatarKim-Anh Tran <kimanh@chromium.org>
    Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
    Reviewed-by: 's avatarIgor Sheludko <ishell@chromium.org>
    Commit-Queue: Igor Sheludko <ishell@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#78432}
    099cb420
builtins-console.cc 11.5 KB