All CLA requirements met.

👎 this duplicates information that's already available in the ctor. To know what kind of error happened you can use an instanceof-check or the ctor-name if you like.

👎 this duplicates information that's already available in the ctor. To know what kind of error happened you can use an instanceof-check or the ctor-name if you like.

It seems that there's no information in the prototype chain about the specific kind of filesystem error (file not found/no permissions/etc.).

https://github.com/microsoft/vscode/blob/master/src/vs/workbench/api/common/extHostTypes.ts#L2305

Are you suggesting subclassing FileSystemError for each specific type, making its static methods return the appropriate subclasses, and expose the subclasses through the api?

Are you suggesting subclassing FileSystemError for each specific type, making its static methods return the appropriate subclasses, and expose the subclasses through the api?

Oh, I am sorry. I thought we already had that... Now your PR makes much more sense but I would keep it more minimal tbh. How about using the code-argument as name of the error, like this.name = code. That would be minimal and should be sufficient.

this.name is already being set by markAsFileSystemProviderError(). And toFileSystemProviderErorrCode() just tries to parse that to tell what happened exactly.

https://github.com/microsoft/vscode/blob/master/src/vs/platform/files/common/files.ts#L346

In an extension, I could just parse error.name myself, but the API does not currently specify its contents. That is, I would somehow have to know that error.name should include EntryNotFound for a "not found" error (and not FileNotFound).

What I don't like that those names - they are internal and don't make much sense in the API, like the error code for FileNotFound is EntryNotFound... So, I'd suggest to simply use the tor-function names, no string-enum or anything just something like this

export class FileSystemError extends Error {
  //...
  /**
   * A code that identifies this error. The value is equal to 
   * the (class) name of the error, e.g `FileNotFound`.
   */
  readonly code: string
}

I've also found some FileSystemError ctor calls in KeyValueLogProvider.ts:

I've changed them to appropriate factory function calls, so the code property is initialized.

https://github.com/microsoft/vscode/blob/2c00388d2d00342347a6a51e6b09649fd2cb6103/src/vs/workbench/services/log/common/keyValueLogProvider.ts#L62

Thanks @iliazeus. I'll merge and drive this as api-proposal to finalization