Auto merge of #16394 - mckaymatt:line_num_offset__issue_15693, r=SimonSapin

Support line number offsets for inline stylesheets

<!-- Please describe your changes on the following line: -->
This allows accurate line numbers when reporting stylesheet errors.

@jdm This is going to require some effort to merge my changes with other recent changes to `ParserContext`. Because of that I would appreciate a quick sanity check before I put the time into performing the merge.
For example, should I store the `offset` as a u64, or should it be an Option?

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #15693 (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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tests/unit/style/media_queries.rs

@@ -19,8 +19,12 @@ use style_traits::ToCss;
 pub struct CSSErrorReporterTest;
 
 impl ParseErrorReporter for CSSErrorReporterTest {
-    fn report_error(&self, _input: &mut Parser, _position: SourcePosition, _message: &str,
-        _url: &ServoUrl) {
+    fn report_error(&self,
+                    _input: &mut Parser,
+                    _position: SourcePosition,
+                    _message: &str,
+                    _url: &ServoUrl,
+                    _line_number_offset: u64) {
     }
 }
 
@@ -33,7 +37,7 @@ fn test_media_rule<F>(css: &str, callback: F)
     let media_list = Arc::new(lock.wrap(MediaList::empty()));
     let stylesheet = Stylesheet::from_str(
         css, url, Origin::Author, media_list, lock,
-        None, &CSSErrorReporterTest);
+        None, &CSSErrorReporterTest, 0u64);
     let mut rule_count = 0;
     let guard = stylesheet.shared_lock.read();
     media_queries(&guard, &stylesheet.rules.read_with(&guard).0, &mut |mq| {
@@ -62,7 +66,7 @@ fn media_query_test(device: &Device, css: &str, expected_rule_count: usize) {
     let media_list = Arc::new(lock.wrap(MediaList::empty()));
     let ss = Stylesheet::from_str(
         css, url, Origin::Author, media_list, lock,
-        None, &CSSErrorReporterTest);
+        None, &CSSErrorReporterTest, 0u64);
     let mut rule_count = 0;
     ss.effective_style_rules(device, &ss.shared_lock.read(), |_| rule_count += 1);
     assert!(rule_count == expected_rule_count, css.to_owned());

tests/unit/style/rule_tree/bench.rs

@@ -16,9 +16,15 @@ use test::{self, Bencher};
 
 struct ErrorringErrorReporter;
 impl ParseErrorReporter for ErrorringErrorReporter {
-    fn report_error(&self, _input: &mut Parser, position: SourcePosition, message: &str,
-        url: &ServoUrl) {
-        panic!("CSS error: {}\t\n{:?} {}", url.as_str(), position, message);
+    fn report_error(&self,
+                    input: &mut Parser,
+                    position: SourcePosition,
+                    message: &str,
+                    url: &ServoUrl,
+                    line_number_offset: u64) {
+        let location = input.source_location(position);
+        let line_offset = location.line + line_number_offset as usize;
+        panic!("CSS error: {}\t\n{}:{} {}", url.as_str(), line_offset, location.column, message);
     }
 }
 
@@ -51,7 +57,8 @@ fn parse_rules(css: &str) -> Vec<(StyleSource, CascadeLevel)> {
                                  media,
                                  lock,
                                  None,
-                                 &ErrorringErrorReporter);
+                                 &ErrorringErrorReporter,
+                                 0u64);
     let guard = s.shared_lock.read();
     let rules = s.rules.read_with(&guard);
     rules.0.iter().filter_map(|rule| {

tests/unit/style/stylesheets.rs

@@ -65,7 +65,7 @@ fn test_parse_stylesheet() {
     let lock = SharedRwLock::new();
     let media = Arc::new(lock.wrap(MediaList::empty()));
     let stylesheet = Stylesheet::from_str(css, url.clone(), Origin::UserAgent, media, lock,
-                                          None, &CSSErrorReporterTest);
+                                          None, &CSSErrorReporterTest, 0u64);
     let mut namespaces = Namespaces::default();
     namespaces.default = Some(ns!(html));
     let expected = Stylesheet {
@@ -293,16 +293,17 @@ impl ParseErrorReporter for CSSInvalidErrorReporterTest {
                     input: &mut CssParser,
                     position: SourcePosition,
                     message: &str,
-                    url: &ServoUrl) {
+                    url: &ServoUrl,
+                    line_number_offset: u64) {
 
         let location = input.source_location(position);
+        let line_offset = location.line + line_number_offset as usize;
 
         let mut errors = self.errors.lock().unwrap();
-
         errors.push(
             CSSError{
                 url: url.clone(),
-                line: location.line,
+                line: line_offset,
                 column: location.column,
                 message: message.to_owned()
             }
@@ -328,18 +329,18 @@ fn test_report_error_stylesheet() {
     let lock = SharedRwLock::new();
     let media = Arc::new(lock.wrap(MediaList::empty()));
     Stylesheet::from_str(css, url.clone(), Origin::UserAgent, media, lock,
-                         None, &error_reporter);
+                         None, &error_reporter, 5u64);
 
     let mut errors = errors.lock().unwrap();
 
     let error = errors.pop().unwrap();
     assert_eq!("Unsupported property declaration: 'invalid: true;'", error.message);
-    assert_eq!(5, error.line);
+    assert_eq!(10, error.line);
     assert_eq!(9, error.column);
 
     let error = errors.pop().unwrap();
     assert_eq!("Unsupported property declaration: 'display: invalid;'", error.message);
-    assert_eq!(4, error.line);
+    assert_eq!(9, error.line);
     assert_eq!(9, error.column);
 
     // testing for the url

tests/unit/style/viewport.rs

@@ -31,7 +31,8 @@ macro_rules! stylesheet {
             Arc::new($shared_lock.wrap(MediaList::empty())),
             $shared_lock,
             None,
-            &$error_reporter
+            &$error_reporter,
+            0u64
         ))
     }
 }