add errors to facility functions

[goatshriek]

The functions dealing with facilities do not currently properly handle error codes. They should generate appropriate error messages when a failure occurs, so that users checking for errors are properly notified. Additionally, errors should be cleared in the event of success so that an error is not mistakenly identified for a successful call. The affected functions are:

• stumpless_get_facility_string
• stumpless_get_facility_enum
• stumpless_get_facility_enum_from_buffer

General Approach

There are a few details left out of the following approach, for you to fill in as you encounter them. If you find you need help, please ask here or on the project gitter and someone can help you get past the stumbling block.

Add your new tests to the test suite for the facility functions test/function/facility.cpp. Each function should have a new test for error clearing, and the existing tests should be enhanced.

The new tests will cause a failure by misusing a different function in order to purposefully generate an error. stumpless_version_to_string is a simple function to misuse (pass it a NULL arg) as one candidate. Assert that there is in fact an error with EXPECT_ERROR_ID_EQ. It will then call the facility function normally, check the result, and ensure that no error is raised with EXPECT_NO_ERROR. Look to other tests for usage of these expect macros. Ensure that the new tests fail, and then add calls to clear_error in the functions themselves to fix the issue.

For existing tests, add calls to EXPECT_ERROR_ID_EQ with STUMPLESS_INVALID_FACILITY as the expected error. Update the functions themselves to raise this error upon failure, and update the documentation to reflect this behavior.

[Ankaa19]

Hello,
I would like to work on this issue. Could you assign me?
Than you a lot.

[goatshriek]

Sure thing, good luck!