feat: upgrade gogen and use custom go printer output & fix some newline before decl

[luoliwoshang]

Summary

• bump github.com/goplus/gogen to v1.20.2
• add internal/gowrite as the custom Go output path (go/format with a controlled synthetic token.FileSet)
• switch tool/gengo and cmd/gogensig to use internal/gowrite
• adjust parser comment handling: keep one multiline comment as one ast.Comment.Text entry in CommentGroup.List
• update parser/cmp test expectations accordingly
• create const groups lazily to avoid generating unnecessary empty const ()

Why not use gogen's built-in print path?

This change needs full control of the token.FileSet used during printing.

llcppg often generates AST nodes without full original source positions. To keep output stable on newer go/printer, we assign synthetic anchors and line table entries in a specific FileSet. If the final print path does not use the same controllable FileSet, then even with assigned Pos values, comment/declaration spacing can still collapse or drift.

gogen's default print path does not let this PR choose and manage the exact FileSet lifecycle required by that strategy, so this PR uses a custom writer path.

Parser comment behavior

For Go AST/printer compatibility, a multiline block comment should be represented as a single ast.Comment.Text (for example one /* ... */ text), not split into multiple plain lines.

So in parser output we now keep such multiline comments as one CommentGroup.List item. This keeps go/printer behavior correct and stable.

Future refinement: multiline // runs can be split into multiple Comment.Text entries when/if needed.

Context

• Fixed of Updating gogen from v1.19.7 to v1.20.2 causes test failures in TestFromTestdata #635
• convert: lazily create ConstGroup in createEnumItems to avoid empty const nodes #643 is a sub-issue under Updating gogen from v1.19.7 to v1.20.2 causes test failures in TestFromTestdata #635
• Refs build(deps): bump github.com/goplus/llgo from 0.11.6-0.20250824004317-e4218f90d792 to 0.11.6 #589

Validation

• go test ./internal/gowrite -count=1
• go test ./cl/internal/convert -count=1
• cd _xtool/internal/parser && llgo test .

[gemini-code-assist]

Summary of Changes

Hello @luoliwoshang, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves an issue where generated Go ASTs, particularly those derived from C outputs, sometimes lacked per-node source positions. This deficiency, exacerbated by an upgrade to gogen/go-printer, led to unstable and incorrect comment formatting, including collapsing or misplacement. The core solution involves introducing a new gowrite package that applies a synthetic declaration anchor pass before formatting, thereby restoring stable and predictable output without extensively altering the existing conversion pipeline. This change ensures that generated Go code maintains proper structure and readability, especially concerning comments.

Highlights

• New gowrite package introduced: A new gowrite package has been added to ensure stable Go printer output by injecting synthetic declaration anchors, specifically addressing issues with AST nodes missing source positions.
• Tooling migration to gowrite: The gogensig and gengo tools have been migrated to utilize the new gowrite.WriteFile functionality for improved code generation stability.
• Comment parsing adjustment: The parser has been modified to retain comment text without automatically appending a trailing newline, aligning with the new formatting behavior.
• Test expectation files updated: Various expect.json test files have been updated to reflect the changes in comment parsing and formatting.
• Dependency upgrade: The github.com/goplus/gogen dependency has been upgraded to v1.20.2.

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Changelog

• _xtool/internal/parser/parser.go
  • Removed the automatic addition of a trailing newline character to parsed comment text.
• _xtool/internal/parser/testdata/comment/expect.json
  • Updated expected JSON output for comments to remove trailing newline characters.
• _xtool/internal/parser/testdata/forwarddecl1/expect.json
  • Adjusted expected JSON output for comments to remove trailing newline characters.
• _xtool/internal/parser/testdata/typeof/expect.json
  • Modified expected JSON output for comments to remove trailing newline characters.
• cmd/gogensig/gogensig.go
  • Imported the new github.com/goplus/llcppg/internal/gowrite package.
  • Switched from pkg.WriteFile to gowrite.WriteFile for writing generated Go files.
• go.mod
  • Updated the github.com/goplus/gogen dependency from v1.19.7 to v1.20.2.
• go.sum
  • Updated cryptographic checksums for the github.com/goplus/gogen module.
• internal/gowrite/gowrite.go
  • Added a new package gowrite containing WriteFile and WriteTo functions.
  • Implemented assignDeclAnchors to inject synthetic token.Pos values for declarations and comments, stabilizing go/format output.
• internal/gowrite/gowrite_test.go
  • Added unit tests for WriteTo to verify correct formatting of empty and non-empty function bodies.
• tool/gengo.go
  • Imported the new github.com/goplus/llcppg/internal/gowrite package.
  • Switched from pkg.WriteFile to gowrite.WriteFile for writing generated Go files.

Activity

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[gemini-code-assist]

Code Review

This pull request introduces a fix for unstable Go printer output when AST nodes lack position information. The main change is the new internal/gowrite package, which implements a synthetic-position pass before formatting the Go code. This ensures stable comment placement. The change is adopted in gogensig and gengo tools. Additionally, the comment parser is updated to not force a trailing newline, and test expectations are updated accordingly. The gogen dependency is also bumped. The changes look solid and well-implemented. I have one suggestion for improving idiomatic error handling in the new gowrite package.

[fennoai]

Clean approach to stabilizing go/format output for synthetic ASTs. The position-anchor injection technique is well-suited here, and the parser comment fix aligns with go/ast.Comment.Text conventions.

Notable: cl/internal/convert/convert_test.go:248 still uses pkg.WriteFile (with a // todo:reuse same write logic comment), so TestFromTestdata doesn't exercise the new gowrite code path. See inline comments for details.

[codecov]

Codecov Report

❌ Patch coverage is 98.07692% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.30%. Comparing base (d59271a) to head (713b743).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/gowrite/gowrite.go	97.91%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #641      +/-   ##
==========================================
+ Coverage   84.77%   85.30%   +0.52%     
==========================================
  Files          27       28       +1     
  Lines        2318     2415      +97     
==========================================
+ Hits         1965     2060      +95     
- Misses        310      311       +1     
- Partials       43       44       +1     

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