Auto merge of #15278 - atheed:zero-parsing, r=Wafflespeanut

Parsing "0" as Number for line-height and border-image-outset

Fixes #15171 by correctly parsing `0` as `0` (rather than as `0px`, as was the case earlier) for the `line-height` and `border-image-outset` CSS properties. Wrote unit tests for both; `./mach test-unit -p style` passes all tests.

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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 #15171

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- [X] There are tests for these changes.

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tests/unit/style/parsing/border.rs

@@ -104,3 +104,21 @@ fn border_image_outset_should_error_on_negative_number() {
     let result = border_image_outset::parse(&context, &mut parser);
     assert_eq!(result, Err(()));
 }
+
+#[test]
+fn border_image_outset_should_return_number_on_plain_zero() {
+    let url = ServoUrl::parse("http://localhost").unwrap();
+    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let mut parser = Parser::new("0");
+    let result = border_image_outset::parse(&context, &mut parser);
+    assert_eq!(result.unwrap(), parse_longhand!(border_image_outset, "0"));
+}
+
+#[test]
+fn border_image_outset_should_return_length_on_length_zero() {
+    let url = ServoUrl::parse("http://localhost").unwrap();
+    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let mut parser = Parser::new("0em");
+    let result = border_image_outset::parse(&context, &mut parser);
+    assert_eq!(result.unwrap(), parse_longhand!(border_image_outset, "0em"));
+}

tests/unit/style/parsing/inherited_text.rs

@@ -102,3 +102,29 @@ fn webkit_text_stroke_shorthand_should_parse_properly() {
     assert_eq!(result._webkit_text_stroke_color.unwrap(), parse_longhand!(_webkit_text_stroke_color, "red"));
     assert_eq!(result._webkit_text_stroke_width.unwrap(), parse_longhand!(_webkit_text_stroke_width, "thin"));
 }
+
+#[test]
+fn line_height_should_return_number_on_plain_zero() {
+    use media_queries::CSSErrorReporterTest;
+    use servo_url::ServoUrl;
+    use style::properties::longhands::line_height;
+
+    let url = ServoUrl::parse("http://localhost").unwrap();
+    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let mut parser = Parser::new("0");
+    let result = line_height::parse(&context, &mut parser);
+    assert_eq!(result.unwrap(), parse_longhand!(line_height, "0"));
+}
+
+#[test]
+fn line_height_should_return_length_on_length_zero() {
+    use media_queries::CSSErrorReporterTest;
+    use servo_url::ServoUrl;
+    use style::properties::longhands::line_height;
+
+    let url = ServoUrl::parse("http://localhost").unwrap();
+    let context = ParserContext::new(Origin::Author, &url, Box::new(CSSErrorReporterTest));
+    let mut parser = Parser::new("0px");
+    let result = line_height::parse(&context, &mut parser);
+    assert_eq!(result.unwrap(), parse_longhand!(line_height, "0px"));
+}