[tools] internal/astutil: return enclosing node when Select finds no enclosing node
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Hongxiang Jiang (Gerrit)
Dec 15, 2025, 7:57:11 PM (19 hours ago) Dec 15
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Hongxiang Jiang has uploaded the change for review![]( "Open in Gerrit")
Commit message
internal/astutil: return enclosing node when Select finds no enclosing node
Previously, Select returned an error ("no syntax selected") if the
provided range did not wholly enclose any syntax nodes. This behavior
was problematic for point selections (where start == end) or selections
that covered only tokens or whitespace, as callers often still require
the enclosing context (e.g., for code actions or hover information).
Select now returns the enclosing cursor with NoCursor for the start and
end nodes in these cases, rather than returning an error. This allows
callers to inspect the surrounding syntax tree even without a specific
sub-node selection.
This change also documents NoCursor as the sentinel value for checking
validity.
Change-Id: I623cd5bc1b4173970ad1dc3e7baae79aa74cc5de
Change diff
diff --git a/gopls/internal/golang/type_definition.go b/gopls/internal/golang/type_definition.go
index 3de9230..51f8126 100644
--- a/gopls/internal/golang/type_definition.go
+++ b/gopls/internal/golang/type_definition.go
@@ -31,9 +31,9 @@
if err != nil {
return nil, err
}
- cur, ok := pgf.Cursor.FindByPos(start, end)
- if !ok {
- return nil, fmt.Errorf("no enclosing syntax") // can't happen
+ cur, _, _, err := astutil.Select(pgf.Cursor, start, end)
+ if err != nil {
+ return nil, err
}
// Find innermost enclosing expression that has a type.
diff --git a/internal/astutil/util.go b/internal/astutil/util.go
index 6986a51..a022995 100644
--- a/internal/astutil/util.go
+++ b/internal/astutil/util.go
@@ -178,6 +178,10 @@
//
// Select returns the enclosing BlockStmt, the f() CallExpr, and the g() CallExpr.
//
+// If the selection does not wholly enclose any nodes (for example, a
+// point selection at a token position, or a selection of only whitespace),
+// enclosing is returned with zero start and end Cursors.
+//
// Callers that require exactly one syntax tree (e.g. just f() or just
// g()) should check that the returned start and end nodes are
// identical.
@@ -190,7 +194,7 @@
func Select(curFile inspector.Cursor, start, end token.Pos) (_enclosing, _start, _end inspector.Cursor, _ error) {
curEnclosing, ok := curFile.FindByPos(start, end)
if !ok {
- return noCursor, noCursor, noCursor, fmt.Errorf("invalid selection")
+ return NoCursor, NoCursor, NoCursor, fmt.Errorf("invalid selection")
}
// Find the first and last node wholly within the (start, end) range.
@@ -214,7 +218,11 @@
}
}
if !CursorValid(curStart) {
- return noCursor, noCursor, noCursor, fmt.Errorf("no syntax selected")
+ // The selection is valid (inside curEnclosing) but contains no
+ // complete nodes. This happens for point selections (start == end),
+ // or selections covering only tokens/whitespace.
+ // Return the enclosing node so the caller can still use the context.
+ return curEnclosing, NoCursor, NoCursor, nil
}
return curEnclosing, curStart, curEnd, nil
}
@@ -230,4 +238,8 @@
return cur.Inspector() != nil
}
-var noCursor inspector.Cursor
+// NoCursor is the zero value of a Cursor, representing an invalid or
+// absent node. It is returned by functions like Select when no syntax
+// node matches the query. Callers may compare a Cursor against NoCursor
+// to check if it is valid.
+var NoCursor inspector.Cursor
Change information
Files:
- M gopls/internal/golang/type_definition.go
- M internal/astutil/util.go
Change size: S
Delta: 2 files changed, 18 insertions(+), 6 deletions(-)
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Hongxiang Jiang (Gerrit)
Dec 15, 2025, 7:57:20 PM (19 hours ago) Dec 15
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Hongxiang Jiang voted Commit-Queue+1![]( "Open in Gerrit")
| Commit-Queue | +1 |
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Hongxiang Jiang (Gerrit)
Dec 15, 2025, 8:31:05 PM (18 hours ago) Dec 15
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Attention needed from Hongxiang Jiang
Hongxiang Jiang uploaded new patchset![]( "Open in Gerrit")
Hongxiang Jiang uploaded patch set #2 to this change.
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Hongxiang Jiang (Gerrit)
Dec 15, 2025, 8:31:15 PM (18 hours ago) Dec 15
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Hongxiang Jiang voted Commit-Queue+1![]( "Open in Gerrit")
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Hongxiang Jiang (Gerrit)
Dec 15, 2025, 9:09:53 PM (17 hours ago) Dec 15
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Hongxiang Jiang added 2 comments![]( "Open in Gerrit")
Patchset-level comments
File internal/astutil/util.go
Line 225, Patchset 2 (Latest):
return curEnclosing, NoCursor, NoCursor, nilHongxiang Jiang . resolved
I'm not sure this is right way of returning this. This feels weird that the caller have to check the 2nd the 3rd return value against "NoCursor" to figure out if this return value is valid.
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