Dvc: Improve missing output message

[shcheklein]

Command:

dvc run -d code/xml_to_tsv.py -d data/Posts.xml -o data/Posts.tsv python code/xml_to_tsv.py data/Posts.xml data/Posts.tsv

when script xml_to_tsv fails to produce output (no errors), DVC output this message:

Error: Failed to run command: Output 'data/Posts.tsv' error: does not exist

it's ambiguous - not clear if there is a problem with the script (fails to run) or DVC command. Let's try to explain it better.

[ghost]

@shcheklein , is this still relevant? this is the current error message, it is clear for me:

❯ dvc run -o foo 'echo "something"'
Running command:
        echo "something"
something
ERROR: failed to run command - output 'foo' does not exist

Having any troubles?. Hit us up at https://dvc.org/support, we are always happy to help!

[ghost]

Maybe the error shouldn't say failed to run command because the command was, indeed, successful (exit code 0)

[shcheklein]

@mroutis the current message is the same as it was before. Cryptic and confusing. So, it's still relevant. We can come with a way better and user friendly message I hope :)

[efiop]

@shcheklein How is output 'foo' does not exist cryptic? It is clearly stating what is wrong. Do you suggest we add something like Check that your command is indeed creating this output.?

[shcheklein]

Yes. Something like this. Your command executed fine but DVC was not able to detect "data/Posts.tsv" that was specified as an output for the command. Check that your command is indeed creating this output?