Auto merge of #16024 - Wafflespeanut:gal, r=Wafflespeanut

Add parsing/serialisation for 'grid-auto-flow'

Didn't want the work (and review comments) in #15364 to go wasted. Fixes #15313

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components/style/properties/longhand/position.mako.rs

@@ -322,3 +322,89 @@ ${helpers.predefined_type("object-position",
                               products="gecko",
                               boxed=True)}
 % endfor
+
+<%helpers:longhand name="grid-auto-flow"
+        spec="https://drafts.csswg.org/css-grid/#propdef-grid-auto-flow"
+        products="none"
+        animatable="False">
+    use std::fmt;
+    use style_traits::ToCss;
+    use values::HasViewportPercentage;
+    use values::computed::ComputedValueAsSpecified;
+
+    pub type SpecifiedValue = computed_value::T;
+
+    pub mod computed_value {
+        #[derive(PartialEq, Clone, Eq, Copy, Debug)]
+        #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+        pub enum AutoFlow {
+            Row,
+            Column,
+        }
+
+        #[derive(PartialEq, Clone, Eq, Copy, Debug)]
+        #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+        pub struct T {
+            pub autoflow: AutoFlow,
+            pub dense: bool,
+        }
+    }
+
+    no_viewport_percentage!(SpecifiedValue);
+    impl ComputedValueAsSpecified for SpecifiedValue {}
+
+    impl ToCss for computed_value::T {
+        fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+            dest.write_str(match self.autoflow {
+                computed_value::AutoFlow::Column => "column",
+                computed_value::AutoFlow::Row => "row"
+            })?;
+
+            if self.dense { dest.write_str(" dense")?; }
+            Ok(())
+        }
+    }
+
+    #[inline]
+    pub fn get_initial_value() -> computed_value::T {
+        computed_value::T {
+            autoflow: computed_value::AutoFlow::Row,
+            dense: false
+        }
+    }
+
+    /// [ row | column ] || dense
+    pub fn parse(_context: &ParserContext, input: &mut Parser) -> Result<SpecifiedValue, ()> {
+        use self::computed_value::AutoFlow;
+
+        let mut value = None;
+        let mut dense = false;
+
+        while !input.is_exhausted() {
+            match_ignore_ascii_case! { &input.expect_ident()?,
+                "row" if value.is_none() => {
+                    value = Some(AutoFlow::Row);
+                    continue
+                },
+                "column" if value.is_none() => {
+                    value = Some(AutoFlow::Column);
+                    continue
+                },
+                "dense" if !dense => {
+                    dense = true;
+                    continue
+                },
+                _ => return Err(())
+            }
+        }
+
+        if value.is_some() || dense {
+            Ok(computed_value::T {
+                autoflow: value.unwrap_or(AutoFlow::Row),
+                dense: dense,
+            })
+        } else {
+            Err(())
+        }
+    }
+</%helpers:longhand>

tests/unit/style/parsing/position.rs

@@ -142,3 +142,28 @@ fn test_vertical_position() {
     assert!(parse(VerticalPosition::parse, "left right").is_err());
     assert!(parse(VerticalPosition::parse, "20px 30px").is_err());
 }
+
+#[test]
+fn test_grid_auto_flow() {
+    use style::properties::longhands::grid_auto_flow;
+
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "row dense", "row dense");
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "dense row", "row dense");
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "column dense", "column dense");
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "dense column", "column dense");
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "dense", "row dense");
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "row", "row");
+    assert_roundtrip_with_context!(grid_auto_flow::parse, "column", "column");
+
+    // Neither row, column or dense can be repeated
+    assert!(parse(grid_auto_flow::parse, "dense dense").is_err());
+    assert!(parse(grid_auto_flow::parse, "row row").is_err());
+    assert!(parse(grid_auto_flow::parse, "column column").is_err());
+    assert!(parse(grid_auto_flow::parse, "row dense dense").is_err());
+    assert!(parse(grid_auto_flow::parse, "column dense dense").is_err());
+
+    // Only row, column, dense idents are allowed
+    assert!(parse(grid_auto_flow::parse, "dense 1").is_err());
+    assert!(parse(grid_auto_flow::parse, "column 'dense'").is_err());
+    assert!(parse(grid_auto_flow::parse, "column 2px dense").is_err());
+}