x/tools/gopls: unimported imports don't work with empty selector

[muirdm]

In code like:

package main
func main() {
  context.
}

I expected to get candidates from "context" but I get nothing.

/cc @heschik

[gopherbot]

Thank you for filing a gopls issue! Please take a look at the Troubleshooting guide, and make sure that you have provided all of the relevant information here.

[heschik]

Looks like more your bag, it's failing during parsing and never running any completion code at all, I think?

emptysel.go:5:1: expected selector or type assertion, found '}' (and 2 more errors)

[stamblerre]

I don't think so, because we ignore errors in parsing as long as we get an AST back. I think regular completions work fine in this case.

[muirdm]

Completion in general works in this case since you get a parser error, but you also get a best effort *ast.File. The root of the issue seemed to be in imports.ApplyFixes(). It does not handle files with syntax errors since it needs to format the entire file. I wasn't sure if the right approach was to trim to just the imports before calling imports.ApplyFixes, or some change under imports/.

[heschik]

You're both right, of course. CL mailed.

[gopherbot]

Change https://golang.org/cl/209579 mentions this issue: internal/imports: make ApplyFixes work despite syntax errors

[heschik]

I'm noticing what seems to be the same problem if the empty selector is right before a keyword on the next line.

expected selector or type assertion, found 'if' (and 13 more errors)

[muirdm]

Do you have a repro? It seems to work normally for me with a keyword on the next line.

[heschik]

Yeah. Using gopls built at 7a2a8a, inserting base64. at line 207 or on a new line after 211 of format.go causes a parse error. https://golang.org/cl/c/210200/1 fixes the bug because it usually doesn't need to parse the whole file anymore, so maybe it doesn't matter so much.

[heschik]

I think the basic gist of this is that I'm not using cache.parseGo, so I'm not getting AST fixups. Maybe I should be?

[stamblerre]

I don't think any of the AST fixups touch the import spec, but maybe it's worth trying this out?

[heschik]

At the time I had the problem, I was always parsing the whole file. Now I only need to do that when there's no imports yet, but I imagine the problem would still happen.