thodg/libgit2/src

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  • Hash : fa59f18d
    Author : Vicent Marti
    Date : 2011-05-09T20:54:04

    Change error handling mechanism once again Ok, this is the real deal. Hopefully. Here's how it's going to work: - One main method, called `git__throw`, that sets the error code and error message when an error happens. This method must be called in every single place where an error code was being returned previously, setting an error message instead. Example, instead of: return GIT_EOBJCORRUPTED; Use: return git__throw(GIT_EOBJCORRUPTED, "The object is missing a finalizing line feed"); And instead of: [...] { error = GIT_EOBJCORRUPTED; goto cleanup; } Use: [...] { error = git__throw(GIT_EOBJCORRUPTED, "What an error!"); goto cleanup; } The **only** exception to this are the allocation methods, which return NULL on failure but already set the message manually. /* only place where an error code can be returned directly, because the error message has already been set by the wrapper */ if (foo == NULL) return GIT_ENOMEM; - One secondary method, called `git__rethrow`, which can be used to fine-grain an error message and build an error stack. Example, instead of: if ((error = foobar(baz)) < GIT_SUCCESS) return error; You can now do: if ((error = foobar(baz)) < GIT_SUCCESS) return git__rethrow(error, "Failed to do a major operation"); The return of the `git_lasterror` method will be a string in the shape of: "Failed to do a major operation. (Failed to do an internal operation)" E.g. "Failed to open the index. (Not enough permissions to access '/path/to/index')." NOTE: do not abuse this method. Try to write all `git__throw` messages in a descriptive manner, to avoid having to rethrow them to clarify their meaning. This method should only be used in the places where the original error message set by a subroutine is not specific enough. It is encouraged to continue using this style as much possible to enforce error propagation: if ((error = foobar(baz)) < GIT_SUCCESS) return error; /* `foobar` has set an error message, and we are just propagating it */ The error handling revamp will take place in two phases: - Phase 1: Replace all pieces of code that return direct error codes with calls to `git__throw`. This can be done semi-automatically using `ack` to locate all the error codes that must be replaced. - Phase 2: Add some `git__rethrow` calls in those cases where the original error messages are not specific enough. Phase 1 is the main goal. A minor libgit2 release will be shipped once Phase 1 is ready, and the work will start on gradually improving the error handling mechanism by refining specific error messages. OTHER NOTES: - When writing error messages, please refrain from using weasel words. They add verbosity to the message without giving any real information. (<3 Emeric) E.g. "The reference file appears to be missing a carriage return" Nope. "The reference file is missing a carriage return" Yes. - When calling `git__throw`, please try to use more generic error codes so we can eventually reduce the list of error codes to something more reasonable. Feel free to add new, more generic error codes if these are going to replace several of the old ones. E.g. return GIT_EREFCORRUPTED; Can be turned into: return git__throw(GIT_EOBJCORRUPTED, "The reference is corrupted");

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