cli: add version command

[gsilvapt]

• As discussed in LP #1590349, snapcraft should return the version
  number when called like snapcraft version and snapcraft --version.

• Have you followed the guidelines for contributing?
• Have you signed the CLA?
• If this is a bugfix. Have you checked that there is a bug report open for the issue you are trying to fix on bug reports?
• If this is a new feature. Have you discussed the design on the forum?
• Have you successfully run ./runtests.sh static?
• Have you successfully run ./runtests.sh unit?

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[kalikiana]

In general, tests shouldn't print anything - instead I would recommend you do something like self.assertThat(result.output, Equals(snapcraft.__version__)) which will only output the value if it fails.

[kyrofa]

I'd like to see one more test ensuring that the output from --version == the output from version. Because I can tell you right now, it doesn't 😉 .

[kyrofa]

Run both --version and version, and you'll see the output is not exactly the same. Click is using its default template, we need to duplicate that here.

[gsilvapt]

Thank you for your review. Indeed it is important to add that.

But I do not want to hard code the text string before the method returns the version number. Maybe I am missing something from the click framework to also include in the method I wrote? This would actually allow the results to be tested.

[kyrofa]

To quote the click.version_option section in the click docs:

message – custom message to show instead of the default ('%(prog)s, version %(version)s')

I don't have a problem hard-coding that string here. However, if your concern is that Click might change out from under us, you can also add the message parameter where we use version_option to ensure they always stay in sync.

[gsilvapt]

Both methods are now printing the same output and the same text. A test was added to guarantee this.

[kalikiana]

@gsilvapt I see a failure from flake8:
snapcraft/cli/__init__.py:102: error: Unexpected keyword argument "message" for "version_option" /usr/local/lib/mypy/typeshed/third_party/2and3/click/decorators.pyi:174: note: "version_option" defined here

I think you should probably add # type: ignore here, it makes mypy pass - @sergiusens Can you confirm if this the right solution?

[gsilvapt]

I can give that a try, for sure. It's awkward that it passed all tests locally 😅

[kyrofa]

Perfect, thank you!

[kyrofa]

It's almost like it's validating against its own bundled (and apparently old) version of Click. @sergiusens could use some guidance here.

[kyrofa]

Thanks for this, @gsilvapt! We need to figure out the static failure, but that's not really on you. Overall this PR looks good.

[gsilvapt]

Oh, nice! Thank you for reviewing this PR all the time, @kyrofa.
Keep me posted about this issue so I know how to fix if something happen next time.

[sergiusens]

add a constant here with the version message, make it look like the current on in click, from the source:

'%(prog)s, version %(version)s'

[gsilvapt]

I had to hardcode "snapcraft, version %(version)" otherwise it would produce issues.

Thank you for your review. Hopefully I did not mess up commit after a long time (had a couple of busy weeks). If you prefer, I can start over. to avoid multiple commits and such.

[sergiusens]

use the const defined in version

[gsilvapt]

this command changed to `( = MESSAGE_SNAPCRAFT_VERSION,version = snapcraft.version)

[sergiusens]

Hey there, nice job, I only have one request for consistency and book keeping.

Thanks

[gsilvapt]

There is unnecessary white space causing the static tests to fail. If I fix this, some conflicts arise in other files. I need guidance here, if you please. I can push a single commit just to fix the white spaces. I wanted to squash this into the previous commit but it is a no-brainer for me.