feat: support build tags by copying template header over (#688)

.version

@@ -1 +1 @@
-0.2.663
+0.2.664

generator/generator.go

@@ -101,6 +101,9 @@ func (g *generator) generate() (err error) {
 	if err = g.writeGeneratedDateComment(); err != nil {
 		return
 	}
+	if err = g.writeHeader(); err != nil {
+		return
+	}
 	if err = g.writePackage(); err != nil {
 		return
 	}
@@ -132,6 +135,18 @@ func (g *generator) writeGeneratedDateComment() (err error) {
 	return err
 }
 
+func (g *generator) writeHeader() (err error) {
+	if len(g.tf.Header) == 0 {
+		return nil
+	}
+	for _, n := range g.tf.Header {
+		if err := g.writeGoExpression(n); err != nil {
+			return err
+		}
+	}
+	return err
+}
+
 func (g *generator) writePackage() error {
 	var r parser.Range
 	var err error

parser/v2/templatefile.go

@@ -102,7 +102,7 @@ func (p TemplateFileParser) Parse(pi *parse.Input) (tf TemplateFile, ok bool, er
 		}
 		var newLine string
 		newLine, _, _ = parse.NewLine.Parse(pi)
-		tf.Header = append(tf.Header, TemplateFileGoExpression{Expression: NewExpression(line+newLine, from, pi.Position())})
+		tf.Header = append(tf.Header, TemplateFileGoExpression{Expression: NewExpression(line+newLine, from, pi.Position()), BeforePackage: true})
 	}
 
 	// Strip any whitespace between the template declaration and the first template.

parser/v2/templatefile_test.go

@@ -2,10 +2,7 @@ package parser
 
 import (
 	"reflect"
-	"strings"
 	"testing"
-
-	"github.com/google/go-cmp/cmp"
 )
 
 func TestTemplateFileParser(t *testing.T) {
@@ -160,150 +157,6 @@ templ template(
 	})
 }
 
-func TestTemplateFileRoundTrip(t *testing.T) {
-	tests := []struct {
-		name     string
-		input    string
-		expected string
-	}{
-		{
-			name: "template files can be round tripped",
-			input: `package goof
-
-templ Hello() {
-	Hello
-}
-`,
-			expected: `package goof
-
-templ Hello() {
-	Hello
-}
-`,
-		},
-		{
-			name: "template files can start with comments",
-			input: `// Go comment
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-			expected: `// Go comment
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-		},
-		{
-			name: "template files can start with comments, mixed with whitespace",
-			input: `
-// Go comment
-
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-			expected: `
-// Go comment
-
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-		},
-		{
-			name: "template files can start with multiline comments",
-			input: `
-/********************
-* multiline message *
-********************/
-
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-			expected: `
-/********************
-* multiline message *
-********************/
-
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-		},
-		{
-			name: "template files can start with comments, mixed with whitespace",
-			input: `
-// Go comment
-
-/* Multiline comment on a single line */
-
-/*
-
-Multi-line comment on multiple lines
-
-*/
-
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-			expected: `
-// Go comment
-
-/* Multiline comment on a single line */
-
-/*
-
-Multi-line comment on multiple lines
-
-*/
-
-package goof
-
-templ Hello() {
-	Hello
-}
-`,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			tf, err := ParseString(tt.input)
-			if err != nil {
-				t.Fatalf("failed to parse template file: %v", err)
-			}
-
-			sb := new(strings.Builder)
-			err = tf.Write(sb)
-			if err != nil {
-				t.Fatalf("failed to write template file: %v", err)
-			}
-			output := sb.String()
-
-			if diff := cmp.Diff(tt.expected, output); diff != "" {
-				t.Errorf("unexpected output (-want +got):\n%s", diff)
-			}
-		})
-	}
-}
-
 func TestDefaultPackageName(t *testing.T) {
 	tests := []struct {
 		name     string

parser/v2/testdata/templatefile_can_be_round_tripped.txt

@@ -0,0 +1,13 @@
+-- in --
+package goof
+
+templ Hello() {
+	Hello
+}
+
+-- out --
+package goof
+
+templ Hello() {
+	Hello
+}

parser/v2/testdata/templatefile_can_start_with_comments.txt

@@ -0,0 +1,14 @@
+-- in --
+// Go comment
+package goof
+
+templ Hello() {
+	Hello
+}
+-- out --
+// Go comment
+package goof
+
+templ Hello() {
+	Hello
+}

parser/v2/testdata/templatefile_can_start_with_comments_and_whitespace.txt

@@ -0,0 +1,16 @@
+-- in --
+// Go comment
+
+package goof
+
+templ Hello() {
+	Hello
+}
+-- out --
+// Go comment
+
+package goof
+
+templ Hello() {
+	Hello
+}

parser/v2/testdata/templatefile_can_start_with_multiline_comments_and_whitespace.txt

@@ -0,0 +1,20 @@
+-- in --
+/********************
+* multiline message *
+********************/
+
+package goof
+
+templ Hello() {
+	Hello
+}
+-- out --
+/********************
+* multiline message *
+********************/
+
+package goof
+
+templ Hello() {
+	Hello
+}

parser/v2/testdata/templatefile_can_start_with_multiple_comments_and_whitespace.txt

@@ -0,0 +1,32 @@
+-- in --
+// Go comment
+
+/* Multiline comment on a single line */
+
+/*
+
+Multi-line comment on multiple lines
+
+*/
+
+package goof
+
+templ Hello() {
+	Hello
+}
+-- out --
+// Go comment
+
+/* Multiline comment on a single line */
+
+/*
+
+Multi-line comment on multiple lines
+
+*/
+
+package goof
+
+templ Hello() {
+	Hello
+}

parser/v2/testdata/templateheader_with_build_tags.txt

@@ -0,0 +1,10 @@
+-- in --
+//go:build dev
+
+package p
+
+-- out --
+//go:build dev
+
+package p
+

parser/v2/types.go

@@ -172,15 +172,24 @@ type TemplateFileNode interface {
 
 // TemplateFileGoExpression within a TemplateFile
 type TemplateFileGoExpression struct {
-	Expression Expression
+	Expression    Expression
+	BeforePackage bool
 }
 
 func (exp TemplateFileGoExpression) IsTemplateFileNode() bool { return true }
 func (exp TemplateFileGoExpression) Write(w io.Writer, indent int) error {
-	data, err := format.Source([]byte(exp.Expression.Value))
+	in := exp.Expression.Value
+
+	if exp.BeforePackage {
+		in += "\\\\formatstring\npackage p\n\\\\formatstring"
+	}
+	data, err := format.Source([]byte(in))
 	if err != nil {
 		return writeIndent(w, indent, exp.Expression.Value)
 	}
+	if exp.BeforePackage {
+		data = bytes.TrimSuffix(data, []byte("\\\\formatstring\npackage p\n\\\\formatstring"))
+	}
 	_, err = w.Write(data)
 	return err
 }