fix: data race in errs []error pattern (#1073)

Co-authored-by: Adrian Hesketh <adrianhesketh@hushmail.com>

Author: cristaloleg

generator/htmldiff/diff.go

@@ -18,15 +18,15 @@ func DiffStrings(expected, actual string) (diff string, err error) {
 	var wg sync.WaitGroup
 	wg.Add(2)
 
-	var errs []error
+	errs := make([]error, 2)
 
 	// Format expected.
 	go func() {
 		defer wg.Done()
 		e := new(strings.Builder)
 		err := htmlformat.Fragment(e, strings.NewReader(expected))
 		if err != nil {
-			errs = append(errs, fmt.Errorf("expected html formatting error: %w", err))
+			errs[0] = fmt.Errorf("expected html formatting error: %w", err)
 		}
 		expected = e.String()
 	}()
@@ -37,7 +37,7 @@ func DiffStrings(expected, actual string) (diff string, err error) {
 		a := new(strings.Builder)
 		err := htmlformat.Fragment(a, strings.NewReader(actual))
 		if err != nil {
-			errs = append(errs, fmt.Errorf("actual html formatting error: %w", err))
+			errs[1] = fmt.Errorf("actual html formatting error: %w", err)
 		}
 		actual = a.String()
 	}()
@@ -57,15 +57,15 @@ func DiffCtx(ctx context.Context, input templ.Component, expected string) (forma
 	var wg sync.WaitGroup
 	wg.Add(2)
 
-	var errs []error
+	errs := make([]error, 3)
 
 	// Format the expected value.
 	go func() {
 		defer wg.Done()
 		e := new(strings.Builder)
 		err := htmlformat.Fragment(e, strings.NewReader(expected))
 		if err != nil {
-			errs = append(errs, fmt.Errorf("expected html formatting error: %w", err))
+			errs[0] = fmt.Errorf("expected html formatting error: %w", err)
 		}
 		expected = e.String()
 	}()
@@ -77,14 +77,14 @@ func DiffCtx(ctx context.Context, input templ.Component, expected string) (forma
 		defer wg.Done()
 		err := htmlformat.Fragment(actual, r)
 		if err != nil {
-			errs = append(errs, fmt.Errorf("actual html formatting error: %w", err))
+			errs[1] = fmt.Errorf("actual html formatting error: %w", err)
 		}
 	}()
 
 	// Render the component.
 	err = input.Render(ctx, w)
 	if err != nil {
-		errs = append(errs, fmt.Errorf("failed to render component: %w", err))
+		errs[2] = fmt.Errorf("failed to render component: %w", err)
 	}
 	w.Close()
 

generator/test-css-middleware/render_test.go

@@ -2,6 +2,7 @@ package testcssmiddleware
 
 import (
 	_ "embed"
+	"errors"
 	"fmt"
 	"net/http/httptest"
 	"strings"
@@ -20,7 +21,7 @@ var expectedCSS = `.red_050e5e03{color:red;}
 `
 
 func Test(t *testing.T) {
-	var errs []error
+	errs := make([]error, 3)
 	var wg sync.WaitGroup
 	wg.Add(3)
 
@@ -30,7 +31,7 @@ func Test(t *testing.T) {
 		e := new(strings.Builder)
 		err := htmlformat.Fragment(e, strings.NewReader(expected))
 		if err != nil {
-			errs = append(errs, fmt.Errorf("expected html formatting error: %w", err))
+			errs[0] = fmt.Errorf("expected html formatting error: %w", err)
 		}
 		expected = e.String()
 	}()
@@ -50,7 +51,7 @@ func Test(t *testing.T) {
 		a := new(strings.Builder)
 		err := htmlformat.Fragment(a, w.Body)
 		if err != nil {
-			errs = append(errs, fmt.Errorf("actual html formatting error: %w", err))
+			errs[1] = fmt.Errorf("actual html formatting error: %w", err)
 		}
 		actual = a.String()
 	}()
@@ -65,13 +66,16 @@ func Test(t *testing.T) {
 		a := new(strings.Builder)
 		err := htmlformat.Fragment(a, w.Body)
 		if err != nil {
-			errs = append(errs, fmt.Errorf("actual html formatting error: %w", err))
+			errs[2] = fmt.Errorf("actual html formatting error: %w", err)
 		}
 		actualCSS = a.String()
 	}()
 
 	wg.Wait()
 
+	if err := errors.Join(errs...); err != nil {
+		t.Error(err)
+	}
 	if diff := cmp.Diff(expected, actual); diff != "" {
 		t.Error(diff)
 	}