spectral: Handle "no errors" output that produces invalid JSON

[V4G4X]

When spectral lint finds no errors, it outputs []No results with a severity of 'error' found! - concatenating valid JSON with a plain text message.

❯ spectral lint -f json Swagger.yaml                                                                              
[]No results with a severity of 'error' found!

This causes vim.json.decode() to fail.

Add a check for this specific message string before JSON parsing, returning an empty table to indicate no linting errors.

[mfussenegger]

Could this be due to the stream = "both", with No results with a severity of 'error' found! being reported on stderr and [] on stdout? Maybe stream ought to be changed to stdout instead.

[V4G4X]

Doesn't seem to be the case:

❯ spectral lint -f json Swagger.yaml 2>/dev/null
[]No results with a severity of 'error' found!

❯ spectral lint -f json Swagger.yaml 2>&1 1>/dev/null

2>/dev/null should have filtered out(deleted) any stderr part, but we have the whole thing, meaning it's all stdout.
2>&1 1>/dev/null should have filtered out(deleted) any stdout part, but have nothing, meaning it's all stdout.

[mfussenegger]

Thanks for double checking