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perf: skip comment assignment when no comments exist #1473

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perf: skip comment assignment when no comments exist #1473

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fc73aca
perf: skip comment assignment when the file has no comments
jbedard Jun 9, 2026
fad8545
perf: only build the comment-ordering list that is actually used
jbedard Jun 10, 2026
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22 changes: 17 additions & 5 deletions build/lex.go
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Original file line number Diff line number Diff line change
Expand Up @@ -696,7 +696,7 @@ var keywordToken = map[string]int{
// order walks the expression adding it and its subexpressions to the
// preorder and postorder lists.
func (in *input) order(v Expr) {
if v != nil {
if len(in.lineComments) > 0 && v != nil {
in.pre = append(in.pre, v)
}
switch v := v.(type) {
Expand Down Expand Up @@ -832,17 +832,29 @@ func (in *input) order(v Expr) {
in.order(s)
}
}
if v != nil {
if len(in.suffixComments) > 0 && v != nil {
in.post = append(in.post, v)
}
}

// assignComments attaches comments to nearby syntax.
func (in *input) assignComments() {
// Generate preorder and postorder lists.
// Line comments are attached using the preorder list, suffix comments using
// the postorder list (order() builds only the list(s) for the comment kinds
// present). If the file has neither kind, skip the whole-tree walk entirely.
hasLine := len(in.lineComments) > 0
hasSuffix := len(in.suffixComments) > 0
if !hasLine && !hasSuffix {
return
}

in.order(in.file)
in.assignSuffixComments()
in.assignLineComments()
if hasSuffix {
in.assignSuffixComments()
}
if hasLine {
in.assignLineComments()
}
}

func (in *input) assignSuffixComments() {
Expand Down