Auto merge of #15237 - samuknet:negative-letter-spacing-word-spacing, r=emilio

Allow negative values for letter-spacing and word-spacing.  Inline Le…

<!-- Please describe your changes on the following line: -->
Allow negative values when parsing `letter-spacing` and `word-spacing`.  Inline `parse_non_negative` in `Length`.

---
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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 #15204 (github issue number if applicable).

<!-- Either: -->
- [x] There are tests for these changes

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5 files changed, 28 insertions, 11 deletions

diff --git a/components/style/properties/longhand/inherited_text.mako.rs b/components/style/properties/longhand/inherited_text.mako.rs
index 741806e9ef5..03b5eb2e33b 100644
--- a/components/style/properties/longhand/inherited_text.mako.rs
+++ b/components/style/properties/longhand/inherited_text.mako.rs
@@ -335,11 +335,11 @@ ${helpers.single_keyword("text-align-last",
         }
     }
 
-    pub fn parse(_context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
+    pub fn parse(context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
         if input.try(|input| input.expect_ident_matching("normal")).is_ok() {
             Ok(SpecifiedValue::Normal)
         } else {
-            specified::Length::parse_non_negative(input).map(SpecifiedValue::Specified)
+            specified::Length::parse(context, input).map(SpecifiedValue::Specified)
         }
     }
 </%helpers:longhand>
@@ -416,11 +416,11 @@ ${helpers.single_keyword("text-align-last",
         }
     }
 
-    pub fn parse(_context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
+    pub fn parse(context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
         if input.try(|input| input.expect_ident_matching("normal")).is_ok() {
             Ok(SpecifiedValue::Normal)
         } else {
-            specified::LengthOrPercentage::parse_non_negative(input)
+            specified::LengthOrPercentage::parse(context, input)
                                           .map(SpecifiedValue::Specified)
         }
     }
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index 351c692cc9a..99c4a09abf1 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -463,6 +463,7 @@ impl Length {
     }
 
     /// Parse a non-negative length
+    #[inline]
     pub fn parse_non_negative(input: &mut Parser) -> Result<Length, ()> {
         Length::parse_internal(input, AllowedNumericType::NonNegative)
     }
diff --git a/tests/unit/style/parsing/inherited_text.rs b/tests/unit/style/parsing/inherited_text.rs
index fc77e7318e5..c8cea6aac29 100644
--- a/tests/unit/style/parsing/inherited_text.rs
+++ b/tests/unit/style/parsing/inherited_text.rs
@@ -8,6 +8,29 @@ use style::parser::ParserContext;
 use style::stylesheets::Origin;
 
 #[test]
+fn negative_letter_spacing_should_parse_properly() {
+    use style::properties::longhands::letter_spacing;
+    use style::properties::longhands::letter_spacing::SpecifiedValue;
+    use style::values::specified::length::{Length, NoCalcLength, FontRelativeLength};
+
+    let negative_value = parse_longhand!(letter_spacing, "-0.5em");
+    let expected = SpecifiedValue::Specified(Length::NoCalc(NoCalcLength::FontRelative(FontRelativeLength::Em(-0.5))));
+    assert_eq!(negative_value, expected);
+}
+
+#[test]
+fn negative_word_spacing_should_parse_properly() {
+    use style::properties::longhands::word_spacing;
+    use style::properties::longhands::word_spacing::SpecifiedValue;
+    use style::values::specified::length::{NoCalcLength, LengthOrPercentage, FontRelativeLength};
+
+    let negative_value = parse_longhand!(word_spacing, "-0.5em");
+    let expected = SpecifiedValue::Specified(LengthOrPercentage::Length(NoCalcLength::FontRelative(
+                                             FontRelativeLength::Em(-0.5))));
+    assert_eq!(negative_value, expected);
+}
+
+#[test]
 fn text_emphasis_style_longhand_should_parse_properly() {
     use style::properties::longhands::text_emphasis_style;
     use style::properties::longhands::text_emphasis_style::{ShapeKeyword, SpecifiedValue, KeywordValue};
@@ -79,7 +102,6 @@ fn test_text_emphasis_position() {
     assert_eq!(left_under, SpecifiedValue(HorizontalWritingModeValue::Under, VerticalWritingModeValue::Left));
 }
 
-
 #[test]
 fn webkit_text_stroke_shorthand_should_parse_properly() {
     use media_queries::CSSErrorReporterTest;
diff --git a/tests/wpt/metadata-css/css-text-3_dev/html/text-word-spacing-001.htm.ini b/tests/wpt/metadata-css/css-text-3_dev/html/text-word-spacing-001.htm.ini
deleted file mode 100644
index 39a078b78a4..00000000000
--- a/tests/wpt/metadata-css/css-text-3_dev/html/text-word-spacing-001.htm.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[text-word-spacing-001.htm]
-  type: reftest
-  expected: FAIL
diff --git a/tests/wpt/metadata-css/css21_dev/html4/c542-letter-sp-001.htm.ini b/tests/wpt/metadata-css/css21_dev/html4/c542-letter-sp-001.htm.ini
deleted file mode 100644
index d6d93651343..00000000000
--- a/tests/wpt/metadata-css/css21_dev/html4/c542-letter-sp-001.htm.ini
+++ /dev/null
@@ -1,3 +0,0 @@
-[c542-letter-sp-001.htm]
-  type: reftest
-  expected: FAIL