wip - comments

examples/sample2.hcl

@@ -1,9 +1,8 @@
-service "cat" {
-  process "main" {
-    command = ["/usr/local/bin/awesome-app", "server"]
-  }
+# Arithmetic with literals and application-provided variables
+sum = 1 + addend
 
-  process "mgmt" {
-    command = ["/usr/local/bin/awesome-app", "mgmt"]
-  }
-}
+# String interpolation and templates
+message = "Hello, ${name}!"
+
+# Application-provided functions
+shouty_message = upper(message)

pkg/yqlib/decoder_hcl.go

@@ -64,8 +64,9 @@ func extractLineComment(src []byte, endPos int) string {
 	return ""
 }
 
-// extractLeadingComments extracts comments from the very beginning of the file
-func extractLeadingComments(src []byte) string {
+// extractLeadingComments extracts comments from the very beginning of the file.
+// It returns the comment text and the byte position of the last character in that leading block.
+func extractLeadingComments(src []byte) (string, int) {
 	var comments []string
 	i := 0
 
@@ -74,6 +75,8 @@ func extractLeadingComments(src []byte) string {
 		i++
 	}
 
+	lastPos := -1
+
 	// Extract comment lines from the start
 	for i < len(src) && src[i] == '#' {
 		lineStart := i
@@ -81,6 +84,7 @@ func extractLeadingComments(src []byte) string {
 		for i < len(src) && src[i] != '\n' {
 			i++
 		}
+		lastPos = i - 1
 		comments = append(comments, strings.TrimSpace(string(src[lineStart:i])))
 		// Skip newline
 		if i < len(src) && src[i] == '\n' {
@@ -93,51 +97,46 @@ func extractLeadingComments(src []byte) string {
 	}
 
 	if len(comments) > 0 {
-		return strings.Join(comments, "\n")
+		return strings.Join(comments, "\n"), lastPos
 	}
-	return ""
+	return "", -1
 }
 
 // extractHeadComment extracts comments before a given start position
 func extractHeadComment(src []byte, startPos int) string {
 	var comments []string
 
-	// Look backwards from startPos for comment lines
+	// Start just before the token and skip trailing whitespace
 	i := startPos - 1
-
-	// Skip whitespace backwards to find comment
 	for i >= 0 && (src[i] == ' ' || src[i] == '\t' || src[i] == '\n' || src[i] == '\r') {
 		i--
 	}
 
-	// If we found a #, extract the comment
-	if i >= 0 && src[i] == '#' {
-		// Find the start of this line
-		lineStart := i
-		for lineStart > 0 && src[lineStart-1] != '\n' {
-			lineStart--
-		}
-
-		// Extract from line start to comment end
-		comments = append(comments, strings.TrimSpace(string(src[lineStart:i+1])))
-
-		// Look for more comment lines above this one
-		i = lineStart - 1
-		for i >= 0 && (src[i] == '\n' || src[i] == '\r') {
+	for i >= 0 {
+		// Find line boundaries
+		lineEnd := i
+		for i >= 0 && src[i] != '\n' {
 			i--
 		}
+		lineStart := i + 1
 
-		for i >= 0 && src[i] == '#' {
-			lineStart = i
-			for lineStart > 0 && src[lineStart-1] != '\n' {
-				lineStart--
-			}
-			comments = append([]string{strings.TrimSpace(string(src[lineStart : i+1]))}, comments...)
+		line := strings.TrimRight(string(src[lineStart:lineEnd+1]), " \t\r")
+		trimmed := strings.TrimSpace(line)
 
-			i = lineStart - 1
-			for i >= 0 && (src[i] == '\n' || src[i] == '\r') {
-				i--
-			}
+		if trimmed == "" {
+			break
+		}
+
+		if !strings.HasPrefix(trimmed, "#") {
+			break
+		}
+
+		comments = append([]string{trimmed}, comments...)
+
+		// Move to previous line (skip any whitespace/newlines)
+		i = lineStart - 1
+		for i >= 0 && (src[i] == ' ' || src[i] == '\t' || src[i] == '\n' || src[i] == '\r') {
+			i--
 		}
 	}
 
@@ -176,7 +175,9 @@ func (dec *hclDecoder) Decode() (*CandidateNode, error) {
 	root := &CandidateNode{Kind: MappingNode}
 
 	// Extract file-level head comments (comments at the very beginning of the file)
-	if leadingComment := extractLeadingComments(dec.fileBytes); leadingComment != "" {
+	leadingComment, _ := extractLeadingComments(dec.fileBytes)
+	leadingUsed := false
+	if leadingComment != "" {
 		root.HeadComment = leadingComment
 	}
 
@@ -188,7 +189,18 @@ func (dec *hclDecoder) Decode() (*CandidateNode, error) {
 
 		// Attach comments if any
 		attrRange := attrWithName.Attr.Range()
-		if headComment := extractHeadComment(dec.fileBytes, attrRange.Start.Byte); headComment != "" {
+		headComment := extractHeadComment(dec.fileBytes, attrRange.Start.Byte)
+		if !leadingUsed && leadingComment != "" {
+			// Avoid double-applying the leading file comment to the first attribute
+			switch headComment {
+			case leadingComment:
+				headComment = ""
+			case "":
+				headComment = leadingComment
+			}
+			leadingUsed = true
+		}
+		if headComment != "" {
 			valNode.HeadComment = headComment
 		}
 		if lineComment := extractLineComment(dec.fileBytes, attrRange.End.Byte); lineComment != "" {

pkg/yqlib/encoder_hcl.go

@@ -114,22 +114,37 @@ func (he *hclEncoder) injectComments(output []byte, commentMap map[string]string
 	// Convert output to string for easier manipulation
 	result := string(output)
 
-	// Look for head comments at the root level
-	// These are typically comments before the first attribute
+	// Root-level head comment (stored as ".head")
+	for path, comment := range commentMap {
+		if path == ".head" {
+			trimmed := strings.TrimSpace(comment)
+			if trimmed != "" && !strings.HasPrefix(result, trimmed) {
+				result = trimmed + "\n" + result
+			}
+		}
+	}
+
+	// Attribute head comments: insert above matching assignment
 	for path, comment := range commentMap {
 		parts := strings.Split(path, ".")
-		if len(parts) < 2 {
+		if len(parts) != 2 {
 			continue
 		}
 
-		commentType := parts[len(parts)-1] // "head", "line", or "foot"
+		key := parts[0]
+		commentType := parts[1]
+		if commentType != "head" || key == "" {
+			continue
+		}
 
-		if commentType == "head" && len(parts) == 2 {
-			// Root-level head comment - inject at the beginning
-			// Check if comment not already there
-			if !strings.HasPrefix(result, strings.TrimSpace(comment)) {
-				result = comment + "\n" + result
-			}
+		trimmed := strings.TrimSpace(comment)
+		if trimmed == "" {
+			continue
+		}
+
+		re := regexp.MustCompile(`(?m)^(\s*)` + regexp.QuoteMeta(key) + `\s*=`)
+		if re.MatchString(result) {
+			result = re.ReplaceAllString(result, "$1"+trimmed+"\n$0")
 		}
 	}
 

pkg/yqlib/hcl_test.go

@@ -45,6 +45,23 @@ var multipleBlockLabelKeysExpectedYaml = `service:
           - "management"
 `
 
+var roundtripSample = `# Arithmetic with literals and application-provided variables
+sum = 1 + addend
+
+# String interpolation and templates
+message = "Hello, ${name}!"
+
+# Application-provided functions
+shouty_message = upper(message)`
+
+var roundtripSampleExpected = `# Arithmetic with literals and application-provided variables
+sum = 1 + addend
+# String interpolation and templates
+message = "Hello, ${name}!"
+# Application-provided functions
+shouty_message = upper(message)
+`
+
 var hclFormatScenarios = []formatScenario{
 	{
 		description:  "Simple decode",
@@ -250,6 +267,12 @@ var hclFormatScenarios = []formatScenario{
 		expected:     "# Configuration\nport = 8080\n",
 		scenarioType: "roundtrip",
 	},
+	{
+		description:  "roundtrip example",
+		input:        roundtripSample,
+		expected:     roundtripSampleExpected,
+		scenarioType: "roundtrip",
+	},
 }
 
 func testHclScenario(t *testing.T, s formatScenario) {