At least one user was mislead by the "--apply-changes" flag

[MichaelRFairhurst]

cc @devoncarew

Talking to one of our early users, they ran dartdev migrate on a test package. After running the tool, they did not realize that there was a preview or that the preview was important. Instead they saw the advice "rerun with --apply-changes" and did that instead, and missed out on the main benefits of the tool.

We should rewrite the output to point users to the web preview more heavily, like even maybe something as extreme as:

*beep boop beep*: If you are a computer in an automated workflow, you can rerun
with --apply-changes. If you are a human, use the interactive web view to review,
improve, or apply the results:

Open URL http://.....:82340/....

[devoncarew]

It may be enough to print the preview page url in an ansi bold style?

[devoncarew]

Playing with the verbiage sounds good also (use the interactive web view to review, improve, or apply the results), you just may want to steer away from specific computer / human guidance.

[jcollins-g]

We can also check if the output is a terminal, and if so directly pop up a web browser tab pointing to the right URI. While this would have to be implemented at least 3 different ways depending on platform, it would help direct people into the UI and it would cut down on the annoyance factor of cutting and pasting URIs.

[devoncarew]

There's an existing pub package for this (https://pub.dev/packages/browser_launcher), maintained by the Dart team (for use by DevTools, among other tools).

[devoncarew]

Some work for this is here: https://dart-review.googlesource.com/c/sdk/+/138480 (modulo launching in a browser).

[stereotype441]

This has been improved--the new behavior is that by default, the migration tool starts up the preview server. But if --no-web-preview is supplied, the tool still says To apply these changes, re-run the tool with --apply-changes. I still think we should consider improving the verbiage, e.g. as suggested in #40881 (comment).

[stereotype441]

Mike also points out that when --no-web-preview is not supplied, the tool still tells you about --apply-changes. Probably we shouldn't explicitly point the user to this option since we want to discourage its use. They can find it in --help if they really need it.

[srawlins]

This issue should be defined more concretely. It looks like the AIs are:

• Launch the browser (and add a flag, --[no]launch-browser?).

• If the web preview is served, do not print text about --apply-changes.

• The current text is awkward:

  View migration results:
  Visit:
  
    http://localhost:54770/Users/srawlins/code/dart-csslib?authToken=...
  
  to see the migration results. Use the interactive web view to review...
  

  I like the word "suggestions" used earlier in the output. Maybe something like:

  View the migration suggestions by visiting:
  
    http://localhost:54770/Users/srawlins/code/dart-csslib?authToken=...
  
  Use this interactive preview to review...
  

[srawlins]

I've forked off the "launch a browser" idea into its own issue: #41809.