Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/csslib/src/polyfill.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of csslib.parser;
+
+/**
+ * CSS polyfill emits CSS to be understood by older parsers that which do not
+ * understand (var, calc, etc.).
+ */
+class PolyFill {
+  final Messages _messages;
+  final bool _warningsAsErrors;
+  Map<String, VarDefinition> _allVarDefinitions =
+      new Map<String, VarDefinition>();
+
+  Set<StyleSheet> allStyleSheets = new Set<StyleSheet>();
+
+  /**
+   * [_pseudoElements] list of known pseudo attributes found in HTML, any
+   * CSS pseudo-elements 'name::custom-element' is mapped to the manged name
+   * associated with the pseudo-element key.
+   */
+  PolyFill(this._messages, this._warningsAsErrors);
+
+  /**
+   * Run the analyzer on every file that is a style sheet or any component that
+   * has a style tag.
+   */
+  void process(StyleSheet styleSheet, {List<StyleSheet> includes: null}) {
+    if (includes != null) {
+      processVarDefinitions(includes);
+    }
+    processVars(styleSheet);
+
+    // Remove all var definitions for this style sheet.
+    new _RemoveVarDefinitions().visitTree(styleSheet);
+  }
+
+  /** Process all includes looking for var definitions. */
+  void processVarDefinitions(List<StyleSheet> includes) {
+    for (var include in includes) {
+      _allVarDefinitions = (new _VarDefinitionsIncludes(_allVarDefinitions)
+          ..visitTree(include)).varDefs;
+    }
+  }
+
+  void processVars(StyleSheet styleSheet) {
+    // Build list of all var definitions.
+    var mainStyleSheetVarDefs =
+        (new _VarDefAndUsage(this._messages, _allVarDefinitions)
+        ..visitTree(styleSheet)).varDefs;
+
+    // Resolve all definitions to a non-VarUsage (terminal expression).
+    mainStyleSheetVarDefs.forEach((key, value) {
+      for (Expression expr in (value.expression as Expressions).expressions) {
+        mainStyleSheetVarDefs[key] =
+            _findTerminalVarDefinition(_allVarDefinitions, value);
+      }
+    });
+  }
+}
+
+/** Build list of all var definitions in all includes. */
+class _VarDefinitionsIncludes extends Visitor {
+  final Map<String, VarDefinition> varDefs;
+
+  _VarDefinitionsIncludes(this.varDefs);
+
+  void visitTree(StyleSheet tree) {
+    visitStyleSheet(tree);
+  }
+
+  visitVarDefinition(VarDefinition node) {
+    // Replace with latest variable definition.
+    varDefs[node.definedName] = node;
+    super.visitVarDefinition(node);
+ }
+
+  void visitVarDefinitionDirective(VarDefinitionDirective node) {
+    visitVarDefinition(node.def);
+  }
+}
+
+/**
+ * Find var- definitions in a style sheet.
+ * [found] list of known definitions.
+ */
+class _VarDefAndUsage extends Visitor {
+  final Messages _messages;
+  final Map<String, VarDefinition> _knownVarDefs;
+  final Map<String, VarDefinition> varDefs = new Map<String, VarDefinition>();
+
+  VarDefinition currVarDefinition;
+  List<Expression> currentExpressions;
+
+  _VarDefAndUsage(this._messages, this._knownVarDefs);
+
+  void visitTree(StyleSheet tree) {
+    visitStyleSheet(tree);
+  }
+
+  visitVarDefinition(VarDefinition node) {
+    // Replace with latest variable definition.
+    currVarDefinition = node;
+
+    _knownVarDefs[node.definedName] = node;
+    varDefs[node.definedName] = node;
+
+    super.visitVarDefinition(node);
+
+    currVarDefinition = null;
+ }
+
+  void visitVarDefinitionDirective(VarDefinitionDirective node) {
+    visitVarDefinition(node.def);
+  }
+
+  void visitExpressions(Expressions node) {
+    currentExpressions = node.expressions;
+    super.visitExpressions(node);
+    currentExpressions = null;
+  }
+
+  void visitVarUsage(VarUsage node) {
+    if (currVarDefinition != null && currVarDefinition.badUsage) return;
+
+    // Don't process other var() inside of a varUsage.  That implies that the
+    // default is a var() too.  Also, don't process any var() inside of a
+    // varDefinition (they're just place holders until we've resolved all real
+    // usages.
+    var expressions = currentExpressions;
+    var index = expressions.indexOf(node);
+    assert(index >= 0);
+    var def = _knownVarDefs[node.name];
+    if (def != null) {
+      if (def.badUsage) {
+        // Remove any expressions pointing to a bad var definition.
+        expressions.removeAt(index);
+        return;
+      }
+      _resolveVarUsage(currentExpressions, index,
+          _findTerminalVarDefinition(_knownVarDefs, def));
+    } else if (node.defaultValues.any((e) => e is VarUsage)) {
+      // Don't have a VarDefinition need to use default values resolve all
+      // default values.
+      var terminalDefaults = [];
+      for (var defaultValue in node.defaultValues) {
+        terminalDefaults.addAll(resolveUsageTerminal(defaultValue));
+      }
+      expressions.replaceRange(index, index + 1, terminalDefaults);
+    } else if (node.defaultValues.isNotEmpty){
+      // No VarDefinition but default value is a terminal expression; use it.
+      expressions.replaceRange(index, index + 1, node.defaultValues);
+    } else {
+      if (currVarDefinition != null) {
+        currVarDefinition.badUsage = true;
+        var mainStyleSheetDef = varDefs[node.name];
+        if (mainStyleSheetDef != null) {
+          varDefs.remove(currVarDefinition.property);
+        }
+      }
+      // Remove var usage that points at an undefined definition.
+      expressions.removeAt(index);
+      _messages.warning("Variable is not defined.", node.span);
+    }
+
+    var oldExpressions = currentExpressions;
+    currentExpressions = node.defaultValues;
+    super.visitVarUsage(node);
+    currentExpressions = oldExpressions;
+  }
+
+  List<Expression> resolveUsageTerminal(VarUsage usage) {
+    var result = [];
+
+    var varDef = _knownVarDefs[usage.name];
+    var expressions;
+    if (varDef == null) {
+      // VarDefinition not found try the defaultValues.
+      expressions = usage.defaultValues;
+    } else {
+      // Use the VarDefinition found.
+      expressions = (varDef.expression as Expressions).expressions;
+    }
+
+    for (var expr in expressions) {
+      if (expr is VarUsage) {
+        // Get terminal value.
+        result.addAll(resolveUsageTerminal(expr));
+      }
+    }
+
+    // We're at a terminal just return the VarDefinition expression.
+    if (result.isEmpty && varDef != null) {
+      result = (varDef.expression as Expressions).expressions;
+    }
+
+    return result;
+  }
+
+  _resolveVarUsage(List<Expressions> expressions, int index,
+                   VarDefinition def) {
+    var defExpressions = (def.expression as Expressions).expressions;
+    expressions.replaceRange(index, index + 1, defExpressions);
+  }
+}
+
+/** Remove all var definitions. */
+class _RemoveVarDefinitions extends Visitor {
+  void visitTree(StyleSheet tree) {
+    visitStyleSheet(tree);
+  }
+
+  void visitStyleSheet(StyleSheet ss) {
+    ss.topLevels.removeWhere((e) => e is VarDefinitionDirective);
+    super.visitStyleSheet(ss);
+  }
+
+  void visitDeclarationGroup(DeclarationGroup node) {
+    node.declarations.removeWhere((e) => e is VarDefinition);
+    super.visitDeclarationGroup(node);
+  }
+}
+
+/** Find terminal definition (non VarUsage implies real CSS value). */
+VarDefinition _findTerminalVarDefinition(Map<String, VarDefinition> varDefs,
+    VarDefinition varDef) {
+  var expressions = varDef.expression as Expressions;
+  for (var expr in expressions.expressions) {
+    if (expr is VarUsage) {
+      var usageName = (expr as VarUsage).name;
+      var foundDef = varDefs[usageName];
+
+      // If foundDef is unknown check if defaultValues; if it exist then resolve
+      // to terminal value.
+      if (foundDef == null) {
+        // We're either a VarUsage or terminal definition if in varDefs;
+        // either way replace VarUsage with it's default value because the
+        // VarDefinition isn't found.
+        var defaultValues = (expr as VarUsage).defaultValues;
+        var replaceExprs = expressions.expressions;
+        assert(replaceExprs.length == 1);
+        replaceExprs.replaceRange(0, 1, defaultValues);
+        return varDef;
+      }
+      if (foundDef is VarDefinition) {
+        return _findTerminalVarDefinition(varDefs, foundDef);
+      }
+    } else {
+      // Return real CSS property.
+      return varDef;
+    }
+  }
+
+  // Didn't point to a var definition that existed.
+  return varDef;
+}