Refactor how generated result types are handled (#3564)

* Refactor how generated result types are handled

Make the generated result type root a global variable similar to the expression root.
Remove the dependencies on the go-diff package, use testify instead.

* Fix linter issues

codegen/doc.go

@@ -6,7 +6,7 @@ In particular package codegen defines the data structure that represents a
 generated file (see File) which is composed of sections, each corresponding to a
 Go text template and accompanying data used to render the final code.
 
-THe package also include functions that can generate code that transforms a
+The package also includes functions that generate code to transform a
 given type into another (see GoTransform).
 */
 package codegen

codegen/go_transform_helpers_test.go

@@ -3,6 +3,9 @@ package codegen
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"goa.design/goa/v3/codegen/testdata"
 	"goa.design/goa/v3/expr"
 )
@@ -29,40 +32,27 @@ func TestGoTransformHelpers(t *testing.T) {
 		Type        expr.DataType
 		HelperNames []string
 	}{
-		{"simple", simple, []string{}},
+		{"simple", simple, nil},
 		{"recursive", recursive, []string{"transformRecursiveToRecursive"}},
 		{"composite", composite, []string{"transformSimpleToSimple"}},
 		{"deep", deep, []string{"transformCompositeToComposite", "transformSimpleToSimple"}},
 		{"deep-array", deepArray, []string{"transformCompositeToComposite", "transformSimpleToSimple"}},
-		{"simple-alias", simpleAlias, []string{}},
-		{"nested-map-alias", mapAlias, []string{}},
-		{"array-map-alias", arrayMapAlias, []string{}},
+		{"simple-alias", simpleAlias, nil},
+		{"nested-map-alias", mapAlias, nil},
+		{"array-map-alias", arrayMapAlias, nil},
 		{"result-type-collection", collection, []string{"transformResultTypeToResultType"}},
 	}
 	for _, c := range tc {
 		t.Run(c.Name, func(t *testing.T) {
-			if c.Type == nil {
-				t.Fatal("source type not found in testdata")
-			}
+			require.NotNil(t, c.Type, "source type not found in testdata")
 			_, funcs, err := GoTransform(&expr.AttributeExpr{Type: c.Type}, &expr.AttributeExpr{Type: c.Type}, "source", "target", defaultCtx, defaultCtx, "", true)
-			if err != nil {
-				t.Fatal(err)
-			}
-			if len(funcs) != len(c.HelperNames) {
-				t.Errorf("invalid helpers count, got: %d, expected %d", len(funcs), len(c.HelperNames))
-			} else {
-				var diffs []string
-				actual := make([]string, len(funcs))
-				for i, f := range funcs {
-					actual[i] = f.Name
-					if c.HelperNames[i] != f.Name {
-						diffs = append(diffs, f.Name)
-					}
-				}
-				if len(diffs) > 0 {
-					t.Errorf("invalid helper names, got: %v, expected: %v", actual, c.HelperNames)
-				}
+			require.NoError(t, err)
+			assert.Equal(t, len(c.HelperNames), len(funcs), "invalid helpers count")
+			var actual []string
+			for _, f := range funcs {
+				actual = append(actual, f.Name)
 			}
+			assert.Equal(t, c.HelperNames, actual, "invalid helper names")
 		})
 	}
 }

codegen/go_transform_test.go

@@ -3,6 +3,9 @@ package codegen
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"goa.design/goa/v3/codegen/testdata"
 	"goa.design/goa/v3/expr"
 )
@@ -182,20 +185,12 @@ func TestGoTransform(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			for _, c := range cases {
 				t.Run(c.Name, func(t *testing.T) {
-					if c.Source == nil {
-						t.Fatal("source type not found in testdata")
-					}
-					if c.Target == nil {
-						t.Fatal("target type not found in testdata")
-					}
+					require.NotNil(t, c.Source)
+					require.NotNil(t, c.Target)
 					code, _, err := GoTransform(&expr.AttributeExpr{Type: c.Source}, &expr.AttributeExpr{Type: c.Target}, "source", "target", c.SourceCtx, c.TargetCtx, "", true)
-					if err != nil {
-						t.Fatal(err)
-					}
+					require.NoError(t, err)
 					code = FormatTestCode(t, "package foo\nfunc transform(){\n"+code+"}")
-					if code != c.Code {
-						t.Errorf("invalid code, got:\n%s\ngot vs. expected:\n%s", code, Diff(t, code, c.Code))
-					}
+					assert.Equal(t, c.Code, code)
 				})
 			}
 		})

codegen/go_transform_union_test.go

@@ -3,6 +3,9 @@ package codegen
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
 	"goa.design/goa/v3/codegen/testdata"
 	"goa.design/goa/v3/expr"
 )
@@ -41,14 +44,9 @@ func TestGoTransformUnion(t *testing.T) {
 	for _, c := range tc {
 		t.Run(c.Name, func(t *testing.T) {
 			code, _, err := GoTransform(c.Source, c.Target, "source", "target", defaultCtx, defaultCtx, "", true)
-			if err != nil {
-				t.Errorf("unexpected error %s", err)
-				return
-			}
+			require.NoError(t, err)
 			code = FormatTestCode(t, "package foo\nfunc transform(){\n"+code+"}")
-			if code != c.Expected {
-				t.Errorf("invalid code, got:\n%s\ngot vs. expected:\n%s", code, Diff(t, code, c.Expected))
-			}
+			assert.Equal(t, c.Expected, code)
 		})
 	}
 }

codegen/service/convert_test.go

@@ -261,17 +261,17 @@ func runDSL(t *testing.T, dsl func()) *expr.RootExpr {
 	Services = make(ServicesData)
 	eval.Reset()
 	expr.Root = new(expr.RootExpr)
-	err := eval.Register(expr.Root)
-	require.NoError(t, err)
+	expr.GeneratedResultTypes = new(expr.ResultTypesRoot)
+	require.NoError(t, eval.Register(expr.Root))
+	require.NoError(t, eval.Register(expr.GeneratedResultTypes))
 	expr.Root.API = expr.NewAPIExpr("test api", func() {})
 	expr.Root.API.Servers = []*expr.ServerExpr{expr.Root.API.DefaultServer()}
 
 	// run DSL (first pass)
 	require.True(t, eval.Execute(dsl, nil))
 
 	// run DSL (second pass)
-	err = eval.RunDSL()
-	require.NoError(t, err)
+	require.NoError(t, eval.RunDSL())
 
 	// return generated root
 	return expr.Root

codegen/service/endpoint_test.go

@@ -38,7 +38,6 @@ func TestEndpoint(t *testing.T) {
 	for _, c := range cases {
 		t.Run(c.Name, func(t *testing.T) {
 			codegen.RunDSL(t, c.DSL)
-			expr.Root.GeneratedTypes = &expr.GeneratedRoot{}
 			require.Len(t, expr.Root.Services, 1)
 			fs := EndpointFile("goa.design/goa/example", expr.Root.Services[0])
 			require.NotNil(t, fs)

codegen/service/example_svc_test.go

@@ -33,7 +33,6 @@ func TestExampleServiceFiles(t *testing.T) {
 		for _, c := range cases {
 			t.Run(c.Name, func(t *testing.T) {
 				codegen.RunDSL(t, c.DSL)
-				expr.Root.GeneratedTypes = &expr.GeneratedRoot{}
 				require.Len(t, expr.Root.Services, 3)
 				fs := ExampleServiceFiles("", expr.Root)
 				require.Len(t, fs, 3)

codegen/testing.go

@@ -4,36 +4,26 @@ import (
 	"bytes"
 	"fmt"
 	"os"
-	"os/exec"
 	"strings"
 	"testing"
 
+	"github.com/stretchr/testify/require"
 	"goa.design/goa/v3/eval"
 	"goa.design/goa/v3/expr"
-
-	"github.com/sergi/go-diff/diffmatchpatch"
 )
 
 // RunDSL returns the DSL root resulting from running the given DSL.
 func RunDSL(t *testing.T, dsl func()) *expr.RootExpr {
 	t.Helper()
 	eval.Reset()
 	expr.Root = new(expr.RootExpr)
-	expr.Root.GeneratedTypes = &expr.GeneratedRoot{}
-	if err := eval.Register(expr.Root); err != nil {
-		t.Fatal(err)
-	}
-	if err := eval.Register(expr.Root.GeneratedTypes); err != nil {
-		t.Fatal(err)
-	}
+	expr.GeneratedResultTypes = new(expr.ResultTypesRoot)
+	require.NoError(t, eval.Register(expr.Root))
+	require.NoError(t, eval.Register(expr.GeneratedResultTypes))
 	expr.Root.API = expr.NewAPIExpr("test api", func() {})
 	expr.Root.API.Servers = []*expr.ServerExpr{expr.Root.API.DefaultServer()}
-	if !eval.Execute(dsl, nil) {
-		t.Fatal(eval.Context.Error())
-	}
-	if err := eval.RunDSL(); err != nil {
-		t.Fatal(err)
-	}
+	require.True(t, eval.Execute(dsl, nil), eval.Context.Error())
+	require.NoError(t, eval.RunDSL())
 	return expr.Root
 }
 
@@ -52,22 +42,16 @@ func SectionsCode(t *testing.T, sections []*SectionTemplate) string {
 }
 
 // SectionCodeFromImportsAndMethods generates and formats the code for given import and method definition sections.
-func SectionCodeFromImportsAndMethods(t *testing.T, importSection *SectionTemplate, methodSection *SectionTemplate) string {
+func SectionCodeFromImportsAndMethods(t *testing.T, importSection, methodSection *SectionTemplate) string {
 	t.Helper()
 	var code bytes.Buffer
-	if err := importSection.Write(&code); err != nil {
-		t.Fatal(err)
-	}
-
+	require.NoError(t, importSection.Write(&code))
 	return sectionCodeWithPrefix(t, methodSection, code.String())
 }
 
 func sectionCodeWithPrefix(t *testing.T, section *SectionTemplate, prefix string) string {
 	var code bytes.Buffer
-	if err := section.Write(&code); err != nil {
-		t.Fatal(err)
-	}
-
+	require.NoError(t, section.Write(&code))
 	codestr := code.String()
 
 	if len(prefix) > 0 {
@@ -83,50 +67,23 @@ func FormatTestCode(t *testing.T, code string) string {
 	t.Helper()
 	tmp := CreateTempFile(t, code)
 	defer os.Remove(tmp)
-	if err := finalizeGoSource(tmp); err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, finalizeGoSource(tmp))
 	content, err := os.ReadFile(tmp)
-	if err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, err)
 	return strings.Join(strings.Split(string(content), "\n")[2:], "\n")
 }
 
-// Diff returns a diff between s1 and s2. It uses the diff tool if installed
-// otherwise degrades to using the dmp package.
-func Diff(t *testing.T, s1, s2 string) string {
-	_, err := exec.LookPath("diff")
-	supportsDiff := (err == nil)
-	if !supportsDiff {
-		dmp := diffmatchpatch.New()
-		diffs := dmp.DiffMain(s1, s2, false)
-		return dmp.DiffPrettyText(diffs)
-	}
-	left := CreateTempFile(t, s1)
-	right := CreateTempFile(t, s2)
-	defer os.Remove(left)
-	defer os.Remove(right)
-	cmd := exec.Command("diff", left, right)
-	diffb, _ := cmd.CombinedOutput()
-	return strings.ReplaceAll(string(diffb), "\t", " ␉ ")
-}
-
 // CreateTempFile creates a temporary file and writes the given content.
 // It is used only for testing.
 func CreateTempFile(t *testing.T, content string) string {
 	t.Helper()
 	f, err := os.CreateTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, err)
 	_, err = f.WriteString(content)
 	if err != nil {
 		os.Remove(f.Name())
 		t.Fatal(err)
 	}
-	if err := f.Close(); err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, f.Close())
 	return f.Name()
 }

codegen/validation_test.go

@@ -3,6 +3,8 @@ package codegen
 import (
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+
 	"goa.design/goa/v3/codegen/testdata"
 	"goa.design/goa/v3/expr"
 )
@@ -66,18 +68,14 @@ func TestRecursiveValidationCode(t *testing.T) {
 			ctx := NewAttributeContext(c.Pointer, false, c.UseDefault, "", scope)
 			code := ValidationCode(&expr.AttributeExpr{Type: c.Type}, nil, ctx, c.Required, expr.IsAlias(c.Type), false, "target")
 			code = FormatTestCode(t, "package foo\nfunc Validate() (err error){\n"+code+"}")
-			if code != c.Code {
-				t.Errorf("invalid code, got:\n%s\ngot vs. expected:\n%s", code, Diff(t, code, c.Code))
-			}
+			assert.Equal(t, c.Code, code)
 		})
 	}
 	// Special case of unions with views
 	t.Run("union-with-view", func(t *testing.T) {
 		ctx := NewAttributeContext(false, false, false, "", scope)
 		code := ValidationCode(&expr.AttributeExpr{Type: unionT}, nil, ctx, true, false, true, "target")
 		code = FormatTestCode(t, "package foo\nfunc Validate() (err error){\n"+code+"}")
-		if code != testdata.UnionWithViewValidationCode {
-			t.Errorf("invalid code, got:\n%s\ngot vs. expected:\n%s", code, Diff(t, code, testdata.UnionWithViewValidationCode))
-		}
+		assert.Equal(t, testdata.UnionWithViewValidationCode, code)
 	})
 }

dsl/http.go

@@ -962,7 +962,7 @@ func Body(args ...any) {
 		if rt, ok := attr.Type.(*expr.ResultTypeExpr); ok && expr.IsArray(rt.Type) {
 			// If the attribute type is a result type collection add the type to the
 			// GeneratedTypes so that the type's DSLFunc is executed.
-			*expr.Root.GeneratedTypes = append(*expr.Root.GeneratedTypes, rt)
+			expr.GeneratedResultTypes.Append(rt)
 		}
 		if len(args) > 1 {
 			var ok bool

dsl/result_type.go

@@ -106,19 +106,19 @@ func ResultType(identifier string, args ...any) *expr.ResultTypeExpr {
 	}
 	canonicalID := expr.CanonicalIdentifier(identifier)
 	// Validate that result type identifier doesn't clash
-	for _, rt := range expr.Root.ResultTypes {
-		if re := rt.(*expr.ResultTypeExpr); re.Identifier == canonicalID {
+	for _, rt := range *expr.GeneratedResultTypes {
+		if rt.Identifier == canonicalID {
 			eval.ReportError(
 				"result type %#v with canonical identifier %#v is defined twice",
 				identifier, canonicalID)
 			return nil
 		}
 	}
-	// Now save the type in the API result types map
-	mt := expr.NewResultTypeExpr(typeName, identifier, fn)
-	expr.Root.ResultTypes = append(expr.Root.ResultTypes, mt)
+	// Add the type to the generated types root for later evaluation.
+	rt := expr.NewResultTypeExpr(typeName, identifier, fn)
+	expr.Root.ResultTypes = append(expr.Root.ResultTypes, rt)
 
-	return mt
+	return rt
 }
 
 // TypeName makes it possible to set the Go struct name for a type or result
@@ -201,7 +201,7 @@ func View(name string, adsl ...func()) {
 	switch e := eval.Current().(type) {
 	case *expr.ResultTypeExpr:
 		if e.View(name) != nil {
-			eval.ReportError("multiple expressions for view %#v in result type %#v", name, e.TypeName)
+			eval.ReportError("view %q is defined multiple times in result type %q", name, e.TypeName)
 			return
 		}
 		at := &expr.AttributeExpr{}
@@ -340,11 +340,11 @@ func CollectionOf(v any, adsl ...func()) *expr.ResultTypeExpr {
 	}
 	id = mime.FormatMediaType(rtype, params)
 	canonical := expr.CanonicalIdentifier(id)
-	if mt := expr.Root.GeneratedResultType(canonical); mt != nil {
+	if mt := expr.GeneratedResultType(canonical); mt != nil {
 		// Already have a type for this collection, reuse it.
 		return mt
 	}
-	mt := expr.NewResultTypeExpr("", id, func() {
+	rt := expr.NewResultTypeExpr("", id, func() {
 		rt, ok := eval.Current().(*expr.ResultTypeExpr)
 		if !ok {
 			eval.IncompatibleDSL()
@@ -371,8 +371,8 @@ func CollectionOf(v any, adsl ...func()) *expr.ResultTypeExpr {
 	})
 	// do not execute the DSL right away, will be done last to make sure
 	// the element DSL has run first.
-	*expr.Root.GeneratedTypes = append(*expr.Root.GeneratedTypes, mt)
-	return mt
+	expr.GeneratedResultTypes.Append(rt)
+	return rt
 }
 
 // Reference sets a type or result type reference. The value itself can be a