Increase flexibility of HTML comment parsing.

crates/weaver_semconv_gen/src/parser.rs

@@ -5,6 +5,9 @@
 use crate::Error;
 use crate::GenerateMarkdownArgs;
 use crate::MarkdownGenParameters;
+use nom::bytes::complete::take_until;
+use nom::error::ErrorKind;
+use nom::error::ParseError;
 use nom::multi::many0_count;
 use nom::{
     branch::alt,
@@ -16,8 +19,11 @@ use nom::{
     IResult,
 };
 
+/// exact string we expect for starting a semconv snippet.
+const SEMCONV_HEADER: &str = "semconv";
 /// exact string we expect for ending a semconv snippet.
-const SEMCONV_TRAILER: &str = "<!-- endsemconv -->";
+const SEMCONV_TRAILER: &str = "endsemconv";
+
 
 /// nom parser for tag values.
 fn parse_value(input: &str) -> IResult<&str, &str> {
@@ -78,30 +84,60 @@ fn parse_id(input: &str) -> IResult<&str, &str> {
     ))(input)
 }
 
-/// nom parser for <!-- semconv {id}({args}) -->
-fn parse_markdown_snippet_raw(input: &str) -> IResult<&str, GenerateMarkdownArgs> {
+/// nom parser for HTML comments: `<!--{comment}-->
+fn parse_html_comment(input: &str) -> IResult<&str, &str> {
+    // Comments must have the following format:
+    // The string "<!--".
     let (input, _) = tag("<!--")(input)?;
+    // Optionally, text, with the additional restriction that the text must not start with the string ">", nor start with the string "->", nor contain the strings "<!--", "-->", or "--!>", nor end with the string "<!-".
+    let (input, result) = take_until("-->")(input)?;
+    // The string "-->".
+    let (input, _) = tag("-->")(input)?;
+    Ok((input, result))
+}
+
+/// Parses the semantic convention header and directives for markdown generation.
+fn parse_semconv_snippet_directive(input: &str) -> IResult<&str, GenerateMarkdownArgs> {
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag("semconv")(input)?;
+    let (input, _) = tag(SEMCONV_HEADER)(input)?;
     let (input, _) = multispace0(input)?;
     let (input, id) = parse_id(input)?;
     let (input, opt_args) = opt(parse_markdown_gen_parameters)(input)?;
     let (input, _) = multispace0(input)?;
-    let (input, _) = tag("-->")(input)?;
+    Ok((input, GenerateMarkdownArgs {
+        id: id.to_owned(),
+        args: opt_args.unwrap_or(Vec::new()),
+    },))
+}
 
-    Ok((
-        input,
-        GenerateMarkdownArgs {
-            id: id.to_owned(),
-            args: opt_args.unwrap_or(Vec::new()),
-        },
-    ))
+/// nom parser for <!-- semconv {id}({args}) -->
+fn parse_markdown_snippet_raw(input: &str) -> IResult<&str, GenerateMarkdownArgs> {
+    let (input, snippet) = parse_html_comment(input)?;
+    let (remains, result) = parse_semconv_snippet_directive(snippet)?;
+    if remains.is_empty() {
+        Ok((input, result))
+    } else {
+        Err(nom::Err::Failure(ParseError::from_error_kind(remains, ErrorKind::IsNot)))
+    }
+}
+
+/// nom parser for <!-- endsemconv -->
+fn parse_semconv_trailer(input: &str) -> IResult<&str, ()> {
+    let (input, snippet) = parse_html_comment(input)?;
+    let (snippet, _) = multispace0(snippet)?;
+    let (snippet, _) = tag(SEMCONV_TRAILER)(snippet)?;
+    let (snippet, _) = multispace0(snippet)?;
+    if snippet.is_empty() {
+        Ok((input, ()))
+    } else {
+        Err(nom::Err::Failure(ParseError::from_error_kind(snippet, ErrorKind::Not)))
+    }
+
 }
 
 /// Returns true if the line is the <!-- endsemconv --> marker for markdown snippets.
 pub fn is_semconv_trailer(line: &str) -> bool {
-    // TODO - more flexibility in what we recognize here.
-    line.trim() == SEMCONV_TRAILER
+    matches!(parse_semconv_trailer(line), Ok((rest, _)) if rest.trim().is_empty())
 }
 
 /// Returns true if the line begins a markdown snippet directive and needs tobe parsed.