internal/mod/modimports: use cue/parser.ImportsOnly
Invalid syntax after import declarations should be handled consistently
no matter whether a file started with a package clause or not.
If for any reason cueimports.Read thinks there is invalid syntax
and reads the entire source, such as when a package clause is missing,
stop cue/parser from parsing the entire file as well.
Not only is parsing the entire file in that case wasteful,
but it also leads to errors which aren't particularly useful
when all we care about here is listing imported packages.
While here, remove the use of ParseComments; none of the modimports
users need to parse comments at the top of the file.
This is a remnant from Go, where comments at the top of the file
are important as they may contain build tag directives.
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I35eeade6481b74da7f04240f9ef85da338491f7e
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194961
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>