improve the behavior of format on poorly formed files

[devoncarew]

When editing in build() methods, if the braces/parens aren’t balanced, hitting format will destroy the file. When you go to hit undo, IntelliJ asks if you want to undo through the format operation (which breaks your flow, to have to answer a dialog).

And for context, it's very easy when refactoring build methods - adding, removing, and reordering widgets - to get into a state where the parens are unbalanced.

We should:

• verify that intellij is using the analysis server for formatting when the file is mis-formed
• follow up with dartfmt about being able to format bad files
• have intellij not ask about undoing through a format operation
• possibly, make the IntelliJ formatter (not dartfmt) format better when there are unbalanced (possibly related to https://youtrack.jetbrains.com/issue/WEB-28954)

/cc @alexander-doroshko @jwren

[alexander-doroshko]

verify that intellij is using the analysis server for formatting when the file is mis-formed
follow up with dartfmt about being able to format bad files

IntelliJ reformats the file itself first and then calls dartfmt. But AFAIR dartfmt refuses to work with syntactically incorrect files (even if the problem is trivial), so we end up with an unfortunate result.

have intellij not ask about undoing through a format operation

Hm, it doesn't ask me.

possibly, make the IntelliJ formatter (not dartfmt) format better when this are unbalanced (possibly related to WEB-28954)

Yes, related, and yes, it would be great to make it handle incorrect syntax smarter. Though it might be rather difficult to achieve. It's in fact about parser recovery, as soon as parser handles bad syntax gracefully formatting result will be good enough.

[devoncarew]

IntelliJ reformats the file itself first and then calls dartfmt.

Can we instead only use dartfmt, for files that we would choose to delegate to dartfmt to?

But AFAIR dartfmt refuses to work with syntactically incorrect files (even if the problem is trivial), so we end up with an unfortunate result.

Yup, this I believe by design in dartfmt. I think it would be great to investigate the cost of supporting this feature, as it could really help users fix indent issues. @munificent could speak to how feasible this would be -

[jwren]

On the first point: yes, not calling the IJ reformat feels like the right thing here, or only having it reformat the edited lines.

On the second point: Investment into dartfmt will take time and we should drive it with @munificent, but we shouldn't count on any work being done here to solve this issue for users in the short term.

[alexander-doroshko]

Can we instead only use dartfmt, for files that we would choose to delegate to dartfmt to?

I think we can. At least I hope we can find a way to do it without touching IntelliJ Platform code. But it will effectively mean that we do not reformat syntactically invalid files at all. Even a trivial missing semicolon will block formatting. Is this what we want?

Also, unfortunately, it won't solve the problem like WEB-28954 where we need to reformat only a part of a file (because dartfmt can only format a file as a whole).

Improving IntelliJ's parser recovery sounds reasonable, but may appear to be tricky. I don't have complexity estimates at the moment.

[munificent]

Supporting syntax errors in dartfmt would be a lot of work, and might not give a good user experience in return anyway. Since dartfmt takes a good bit of surrounding context into account when formatting something, tweaking the code near a syntax error could cause a lot of formatting churn.

It may be something worth considering, though. We'd have to figure out how to ensure that dartfmt doesn't drop any user code even if the code has syntax errors.