Adding tests for FinalizeRemovals

compiler/astutil/astutil.go

@@ -492,7 +492,7 @@ func ConcatenateFiles(file *ast.File, tails ...*ast.File) error {
 		for _, imp := range tail.Imports {
 			path := imp.Path.Value
 			if oldImp, ok := imports[path]; ok {
-				// Import is in both files so check if the import name is different.
+				// Import is in both files so check if the import name is not different.
 				if oldName, newName := ImportName(oldImp), ImportName(imp); oldName != newName {
 					return fmt.Errorf("import from of %q can not be concatenated with different name: %q != %q", path, oldName, newName)
 				}

compiler/astutil/astutil_test.go

@@ -588,3 +588,200 @@ func TestSqueezeIdents(t *testing.T) {
 		})
 	}
 }
+
+func TestFinalizeRemovals(t *testing.T) {
+	tests := []struct {
+		name       string
+		src        string
+		perforator func(f *ast.File)
+		want       string
+	}{
+		{
+			name: `no removals`,
+			src: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// bar went home
+				func bar[T any](v T) T { return v }
+				// baz is a mystery
+				var baz int = 42`,
+			perforator: func(f *ast.File) {},
+			want: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// bar went home
+				func bar[T any](v T) T { return v }
+				// baz is a mystery
+				var baz int = 42`,
+		},
+		{
+			name: `removal first decl`,
+			src: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// bar went home
+				func bar[T any](v T) T { return v }
+				// baz is a mystery
+				var baz int = 42`,
+			perforator: func(f *ast.File) {
+				f.Decls[0] = nil
+			},
+			want: `package testpackage
+				// bar went home
+				func bar[T any](v T) T { return v }
+				// baz is a mystery
+				var baz int = 42`,
+		},
+		{
+			name: `removal middle decl`,
+			src: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// bar went home
+				func bar[T any](v T) T { return v }
+				// baz is a mystery
+				var baz int = 42`,
+			perforator: func(f *ast.File) {
+				f.Decls[1] = nil
+			},
+			want: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// baz is a mystery
+				var baz int = 42`,
+		},
+		{
+			name: `removal last decl`,
+			src: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// bar went home
+				func bar[T any](v T) T { return v }
+				// baz is a mystery
+				var baz int = 42`,
+			perforator: func(f *ast.File) {
+				f.Decls[len(f.Decls)-1] = nil
+			},
+			want: `package testpackage
+				// foo took a journey
+				func foo() {}
+				// bar went home
+				func bar[T any](v T) T { return v }`,
+		},
+		{
+			name: `removal one whole value spec`,
+			src: `package testpackage
+				var (
+					foo string   = "foo"
+					bar, baz int = 42, 36
+				)`,
+			perforator: func(f *ast.File) {
+				f.Decls[0].(*ast.GenDecl).Specs[1] = nil
+			},
+			want: `package testpackage
+				var (
+					foo string = "foo"
+				)`,
+		},
+		{
+			name: `removal part of one value spec`,
+			src: `package testpackage
+				var (
+					foo string   = "foo"
+					bar, baz int = 42, 36
+				)`,
+			perforator: func(f *ast.File) {
+				spec := f.Decls[0].(*ast.GenDecl).Specs[1].(*ast.ValueSpec)
+				spec.Names[1] = nil
+				spec.Values[1] = nil
+			},
+			want: `package testpackage
+				var (
+					foo string = "foo"
+					bar int    = 42
+				)`,
+		},
+		{
+			name: `removal all parts of one value spec`,
+			src: `package testpackage
+				var (
+					foo string   = "foo"
+					bar, baz int = 42, 36
+				)`,
+			perforator: func(f *ast.File) {
+				spec := f.Decls[0].(*ast.GenDecl).Specs[1].(*ast.ValueSpec)
+				spec.Names[0] = nil
+				spec.Values[0] = nil
+				spec.Names[1] = nil
+				spec.Values[1] = nil
+			},
+			want: `package testpackage
+				var (
+					foo string = "foo"
+				)`,
+		},
+		{
+			name: `removal all value specs`,
+			src: `package testpackage
+				var (
+					foo string   = "foo"
+					bar, baz int = 42, 36
+				)`,
+			perforator: func(f *ast.File) {
+				decl := f.Decls[0].(*ast.GenDecl)
+				decl.Specs[0] = nil
+				decl.Specs[1] = nil
+			},
+			want: `package testpackage`,
+		},
+		{
+			name: `removal one type spec`,
+			src: `package testpackage
+				type (
+					foo interface{ String() string }
+					bar struct{ baz int }
+				)`,
+			perforator: func(f *ast.File) {
+				decl := f.Decls[0].(*ast.GenDecl)
+				decl.Specs[0] = nil
+			},
+			want: `package testpackage
+				type (
+					bar struct{ baz int }
+				)`,
+		},
+		{
+			name: `removal all type specs`,
+			src: `package testpackage
+				type (
+					foo interface{ String() string }
+					bar struct{ baz int }
+				)`,
+			perforator: func(f *ast.File) {
+				decl := f.Decls[0].(*ast.GenDecl)
+				decl.Specs[0] = nil
+				decl.Specs[1] = nil
+			},
+			want: `package testpackage`,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			st := srctesting.New(t)
+
+			srcFile := st.Parse("testSrc.go", test.src)
+			test.perforator(srcFile)
+			FinalizeRemovals(srcFile)
+			got := srctesting.Format(t, st.FileSet, srcFile)
+
+			// parse and format the expected result so that formatting matches
+			wantFile := st.Parse("testWant.go", test.want)
+			want := srctesting.Format(t, st.FileSet, wantFile)
+
+			if got != want {
+				t.Errorf("Unexpected resulting AST:\n\tgot:  %q\n\twant: %q", got, want)
+			}
+		})
+	}
+}