proposal: go/ast: add CommentGroup.Raw function

[oldme-git]

Proposal Details

Sometimes, We need to get the raw (original) comments to generate some go template files. But CommentGroup.Text does not get the raw (original) comments. This makes it difficult to add comments to the generated template file.
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PR here: https://go-review.googlesource.com/c/go/+/579475

[ianlancetaylor]

CC @griesemer @alandonovan

[gopherbot]

Change https://go.dev/cl/579475 mentions this issue: go.ast: add CommentGroup.Raw function

[adonovan]

The proposed Raw function does not return the original text: windows CR LF line endings have been replaced by "\n" , for example, and a /*...*/ comment at EOF would appear to have a spurious following newline.

Also, the Raw function is easy to write outside the go/ast package, and doesn't require any special intuition or knowledge.

I don't think we should add it to CommentGroup.

[willfaught]

Is there a way to implement it correctly? Perhaps the scanner could have a separate way to get the raw comment token value that the parser can use?

[adonovan]

Perhaps the scanner could have a separate way to get the raw comment token value that the parser can use?

It would be expensive to save the raw comment in the AST, but if you have access to the raw file bytes then certainly you could use the scanner to find the exact position of every comment.

Is there a way to implement it correctly?

I think there should already be sufficient information in the AST to reconstruct the start and end positions of each comment and every byte within them.