Add better logging to CLI

[10kc-zack]

Issue

When running the new v4 CLI, I found that the messages being shown when using the CLI (or lack thereof) made it difficult to understand what what happening. For example:

This works as expected and creates an HTML version of my template:

mjml ./src/templates/my-template.mjml -o my-template.html

while this doesn't work:

mjml ./src/templates/my-template.mjml -o ./dist/my-template.html

When running both of these commands, neither one showed any sort of logging. After looking at #1014, I saw @iRyusa state that the CLI does not create the dist folder to avoid issues, but anyone else running this command would be unable to determine why both commands aren't working. I think it's important to follow the example set by large CLIs like create-react-app (CRA) that show progress of the CLI operations, or at the very least a meaningful error or success message. For example, CRA uses the following success and fail messages when trying to create a new project (which could be analogous to transpiling from MJML to HTML):

Success Case

Fail Case

In the scenario I described above for the MJML CLI, I think messages like this should be included (at the very least):

Success Case

Compiled MJML template to /path/to/my-template.html

Fail Case

Error! Failed to compile MJML template. Directory /path/to/dist does not exist.

MJML version:

v4.0.2

[iRyusa]

Hi @10kc-zack

On this particular case, we've added a message in cli to warn you that output directory doesn't exist.
I'm not against a "verbose" mode/option for the cli, but default output should stick to the strict minimum, because some existing connectors in MJML ecosystem (ex: some ruby gems) interact directly with stdout.

[10kc-zack]

Thanks for your reply @iRyusa. That makes perfect sense why you would want to keep logging to a minimum.

Is the message you mentioned adding in v4.0.2? I was not seeing a message when using the command mjml ./src/templates/my-template.mjml -o ./dist/my-template.html when ./dist did not exist, which prompted me to post the issue.

[iRyusa]

It might only works when output multiple files inside a non-existing directory 🤔

We'll check about that in the 4.1.0 version