When loading a backend config override file, init was doing two things
wrong:
- First, if the file failed to parse, we accidentally didn't return,
which caused a panic due to the parsed body being nil;
- Secondly, we were overzealous with the validation of the file,
allowing only attributes. While most backend configs are attributes
only, the enhanced remote backend body also contains a `workspaces`
block, which we need to support here.
This commit fixes the first bug with an early return and adds test cases
for missing file and intentionally-blank filename (to clear the config).
We also add a schema validation for the backend block, based on the
backend schema itself. This requires constructing an HCL body schema so
that we can call `Content` and check for diagnostic errors.
The result is more useful errors when an invalid backend config override
file is used, while also supporting the enhanced remote backend config
fully.
Does not include tests specific to the remote backend, because the
mocking involved to allow the backend to fully initialize is too
involved to be worth it.
Alisdair McDiarmid