Pre-Flatten Comment Messages in the Parser Rules

slicec/src/parsers/comments/grammar.lalrpop

@@ -80,20 +80,20 @@ InlineLink: LinkTag = {
 }
 
 Section: Message = {
-    <l: @L> <inline_message: (":" <Message?>)?> newline <message_lines: MessageLines?> <r: @R> => {
+    <l: @L> <inline_message: (":" <Message>)?> newline <message_lines: MessageLines?> <r: @R> => {
         let span = Span::new(l, r, comment_parser.file_name);
-        construct_section_message(inline_message.flatten(), message_lines, span)
+        construct_section_message(inline_message, message_lines, span)
     },
 }
 
 MessageLines: Message = {
-    <l: @L> <m: (<Message?> newline)+> <r: @R> => {
+    <l: @L> <m: (<Message> newline)+> <r: @R> => {
         let span = Span::new(l, r, comment_parser.file_name);
         sanitize_message_lines(m, span)
     }
 }
 
-Message = MessageComponent+;
+Message = MessageComponent*;
 
 MessageComponent: MessageComponent = {
     <text: text> => MessageComponent::Text(text.to_owned()),

slicec/src/parsers/comments/grammar.rs

@@ -68,7 +68,7 @@ fn construct_section_message(
 ) -> Message {
     let mut value = message_lines.map(|m| m.value).unwrap_or_default();
 
-    if let Some(mut message) = inline_message {
+    if let Some(mut message) = inline_message.filter(|m| !m.is_empty()) {
         // Remove any leading whitespace from the inline portion of the message.
         if let Some(MessageComponent::Text(text)) = message.first_mut() {
             *text = text.trim_start().to_owned();
@@ -86,19 +86,17 @@ fn construct_section_message(
 }
 
 /// Removes any common leading whitespace from the provided lines and returns the result.
-/// Each element in the vector represents one line of the message.
-/// `None` means the line existed but was empty, `Some(message)` means the line had a message.
+/// Each element in the outermost vector represents one line of the message. These lines may be empty.
 ///
 /// Note that the message's span is not updated to reflect the stripping of common leading whitespace.
-fn sanitize_message_lines(lines: Vec<Option<Vec<MessageComponent>>>, span: Span) -> Message {
+fn sanitize_message_lines(lines: Vec<Vec<MessageComponent>>, span: Span) -> Message {
     // First compute the amount of leading whitespace that is common to every line.
     let mut common_leading_whitespace = usize::MAX;
     for line in &lines {
         // We only check lines that have a message on them (eg: they're non-empty).
-        if let Some(message) = &line {
+        if let Some(message) = line.first() {
             // To check the start of the line, we check the first message component.
-            // It's safe to unwrap because we know the line was non-empty in this block.
-            match message.first().unwrap() {
+            match message {
                 MessageComponent::Text(text) => {
                     // Determine how many whitespace characters are at the beginning of this line,
                     // then take the minimum of this and the amount of whitespace on all the other lines so far.
@@ -118,18 +116,13 @@ fn sanitize_message_lines(lines: Vec<Option<Vec<MessageComponent>>>, span: Span)
     // Now that we know the common leading whitespace, we iterate through the lines again and remove the whitespace.
     let value = lines
         .into_iter()
-        .flat_map(|line| match line {
+        .flat_map(|mut line| {
             // If the message had text, we remove the common leading whitespace and append a newline at the end.
-            Some(mut message) => {
-                if let MessageComponent::Text(text) = message.first_mut().unwrap() {
-                    text.replace_range(..common_leading_whitespace, "");
-                }
-                message.push(MessageComponent::Text("\n".to_owned()));
-                message
+            if let Some(MessageComponent::Text(text)) = line.first_mut() {
+                text.replace_range(..common_leading_whitespace, "");
             }
-
-            // If the line was empty, we create a new message that only contains a newline character.
-            None => vec![MessageComponent::Text("\n".to_owned())],
+            line.push(MessageComponent::Text("\n".to_owned()));
+            line
         })
         .collect();