From af9eb3ec03fb95e8e0f3cf284c7434fc40a9fdde Mon Sep 17 00:00:00 2001
From: Mateusz Poliwczak <mpoliwczak34@gmail.com>
Date: Wed, 2 Oct 2024 11:05:17 +0200
Subject: [PATCH] update tests and add comments

---
 src/go/ast/import.go                          |  2 ++
 src/go/ast/internal/tests/sortimports_test.go | 18 +++++++++++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/go/ast/import.go b/src/go/ast/import.go
index 823396610ce..e6b103790c4 100644
--- a/src/go/ast/import.go
+++ b/src/go/ast/import.go
@@ -207,6 +207,8 @@ func sortSpecs(fset *token.FileSet, f *File, d *GenDecl, specs []Spec) []Spec {
 			deduped = append(deduped, s)
 		} else {
 			p := s.Pos()
+			// This function is exited early when len(specs) <= 1,
+			// so d.Rparen must be populated, d.Rparen.IsValid() return true.
 			if l := lineAt(fset, p); l != lineAt(fset, d.Rparen) {
 				fset.File(p).MergeLine(l)
 			}
diff --git a/src/go/ast/internal/tests/sortimports_test.go b/src/go/ast/internal/tests/sortimports_test.go
index 5832a26317c..c6e53b23f36 100644
--- a/src/go/ast/internal/tests/sortimports_test.go
+++ b/src/go/ast/internal/tests/sortimports_test.go
@@ -83,12 +83,12 @@ import (
 "a"//a
 "a")
 `
-	fs := token.NewFileSet()
-	f, err := parser.ParseFile(fs, "test.go", src, parser.ParseComments|parser.SkipObjectResolution)
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "test.go", src, parser.ParseComments|parser.SkipObjectResolution)
 	if err != nil {
 		t.Fatal(err)
 	}
-	ast.SortImports(fs, f) // should not panic
+	ast.SortImports(fset, f) // should not panic
 }
 
 func TestSortImportsSameLastLine(t *testing.T) {
@@ -99,14 +99,18 @@ import (
 func a() {}
 `
 
-	fs := token.NewFileSet()
-	f, err := parser.ParseFile(fs, "test.go", src, parser.ParseComments|parser.SkipObjectResolution)
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "test.go", src, parser.ParseComments|parser.SkipObjectResolution)
 	if err != nil {
 		t.Fatal(err)
 	}
-	ast.SortImports(fs, f)
+	ast.SortImports(fset, f)
 	fd := f.Decls[1].(*ast.FuncDecl)
-	fdPos := fs.Position(fd.Pos())
+
+	// After SortImports, the Position of the func, should still be at Column == 1.
+	// This is related to the issue: https://go.dev/issue/69183, we were merging lines
+	// incorectly, which caused the position to be Column = 6, Line = 4.
+	fdPos := fset.Position(fd.Pos())
 	if fdPos.Column != 1 {
 		t.Errorf("invalid fdPos.Column = %v; want = 1", fdPos.Column)
 	}