go/ast: update (*File).Imports field in SortImports

Fixes #69694

Change-Id: I7884d42482f4f9d17e7d050d7c7730f20948169d
GitHub-Last-Rev: ecd6efabaa43cc87e31e94002febc9ed4273125a
GitHub-Pull-Request: golang/go#69695
Reviewed-on: https://go-review.googlesource.com/c/go/+/616340
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

src/go/ast/import.go

@@ -51,6 +51,16 @@ func SortImports(fset *token.FileSet, f *File) {
 			}
 		}
 	}
+
+	// Make File.Imports order consistent.
+	f.Imports = f.Imports[:0]
+	for _, decl := range f.Decls {
+		if decl, ok := decl.(*GenDecl); ok && decl.Tok == token.IMPORT {
+			for _, spec := range decl.Specs {
+				f.Imports = append(f.Imports, spec.(*ImportSpec))
+			}
+		}
+	}
 }
 
 func lineAt(fset *token.FileSet, pos token.Pos) int {

src/go/ast/internal/tests/sortimports_test.go

@@ -0,0 +1,78 @@
+// Tests is a helper package to avoid cyclic dependency between go/ast and go/parser.
+package tests
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"testing"
+)
+
+func TestSortImportsUpdatesFileImportsField(t *testing.T) {
+	t.Run("one import statement", func(t *testing.T) {
+		const src = `package test
+
+import (
+	"test"
+	"test" // test comment
+)
+`
+
+		fset := token.NewFileSet()
+		f, err := parser.ParseFile(fset, "test.go", src, parser.ParseComments|parser.SkipObjectResolution)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		ast.SortImports(fset, f)
+
+		// Check that the duplicate import spec is eliminated.
+		importDeclSpecCount := len(f.Decls[0].(*ast.GenDecl).Specs)
+		if importDeclSpecCount != 1 {
+			t.Fatalf("len(f.Decls[0].(*ast.GenDecl).Specs) = %v; want = 1", importDeclSpecCount)
+		}
+
+		// Check that File.Imports is consistent.
+		if len(f.Imports) != 1 {
+			t.Fatalf("len(f.Imports) = %v; want = 1", len(f.Imports))
+		}
+	})
+
+	t.Run("multiple import statements", func(t *testing.T) {
+		const src = `package test
+
+import "unsafe"
+
+import (
+	"package"
+	"package"
+)
+
+import (
+	"test"
+	"test"
+)
+`
+
+		fset := token.NewFileSet()
+		f, err := parser.ParseFile(fset, "test.go", src, parser.ParseComments|parser.SkipObjectResolution)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		ast.SortImports(fset, f)
+
+		// Check that three single-spec import decls remain.
+		for i := range 3 {
+			importDeclSpecCount := len(f.Decls[i].(*ast.GenDecl).Specs)
+			if importDeclSpecCount != 1 {
+				t.Fatalf("len(f.Decls[%v].(*ast.GenDecl).Specs) = %v; want = 1", i, importDeclSpecCount)
+			}
+		}
+
+		// Check that File.Imports is consistent.
+		if len(f.Imports) != 3 {
+			t.Fatalf("len(f.Imports) = %v; want = 3", len(f.Imports))
+		}
+	})
+}