No input flag

[mpacer]

This adds a new --no-input as talked about in few places. This removes prompts and input areas, leaving only the outputs.

This also adds a new test for this feature and removes some of the warnings and extraneous printing that was being done in our tests.

[t-makaro]

I believe exclude_input=True does take out the input prompt with it since it removes the whole block, so having exclude_input_prompt=True seems redundant. I also don't see how a custom template could overwrite that behaviour. I'm not complaining. Really, I just want to make sure that my templates have the expected behaviour.

Also, for symmetry, should there be a --no-output?

[mpacer]

@t-makaro

Yes you're right it is redundant.
A custom template would need to override the null.tpl itself… which is definitely a bizarre anti-pattern that we shouldn't be coding for.

In theory we could include a --no-output flag… but I'm somewhat opposed. Our CLI is already pretty bloated, and I don't think anyone has actually asked for that (since there is always the ClearOutputPreprocessor that can be enabled).

For historical context:
A lot of this functionality was introduced because you couldn't implement a Preprocessor for removing input because then it would not be a valid notebook file. This comes from our constraint that Preprocessors are notebook → notebook transforms… which is one of the cleanest constraints we've got in nbconvert.

[t-makaro]

I was under the impression that the ClearOutputPreprocessor actually overwrote the file. Though I think that only the --clear-output flag does that (since it defaults to inplace if I'm not wrong). So, long as there is a way to convert to another format without outputs and without clearing the original notebook file of outputs then --no-output really isn't needed.

I've definitely seen people ask for no input for generating reports. I personally don't see myself using either no-input or no-output.

[MSeal]

--no-input has a lot of value for reporting purposes. If someone wants outputs hidden for this we can always discuss it in a new issue / pull request

[mpacer]

So I'd like to see this in 5.4 if we're going to be doing the release and there seems to be agreement that this is a good feature that people have been asking for for some time.

[blink1073]

LGTM, thanks!