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Diffstat (limited to 'src/main/java/com/google/escapevelocity/Reparser.java')
-rw-r--r-- | src/main/java/com/google/escapevelocity/Reparser.java | 288 |
1 files changed, 288 insertions, 0 deletions
diff --git a/src/main/java/com/google/escapevelocity/Reparser.java b/src/main/java/com/google/escapevelocity/Reparser.java new file mode 100644 index 0000000..6235bc4 --- /dev/null +++ b/src/main/java/com/google/escapevelocity/Reparser.java @@ -0,0 +1,288 @@ +/* + * Copyright (C) 2015 Google, Inc. + * + * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except + * in compliance with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software distributed under the License + * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express + * or implied. See the License for the specific language governing permissions and limitations under + * the License. + */ +package com.google.escapevelocity; + +import static com.google.escapevelocity.Node.emptyNode; + +import com.google.escapevelocity.DirectiveNode.ForEachNode; +import com.google.escapevelocity.DirectiveNode.IfNode; +import com.google.escapevelocity.DirectiveNode.MacroCallNode; +import com.google.escapevelocity.DirectiveNode.SetNode; +import com.google.escapevelocity.TokenNode.CommentTokenNode; +import com.google.escapevelocity.TokenNode.ElseIfTokenNode; +import com.google.escapevelocity.TokenNode.ElseTokenNode; +import com.google.escapevelocity.TokenNode.EndTokenNode; +import com.google.escapevelocity.TokenNode.EofNode; +import com.google.escapevelocity.TokenNode.ForEachTokenNode; +import com.google.escapevelocity.TokenNode.IfOrElseIfTokenNode; +import com.google.escapevelocity.TokenNode.IfTokenNode; +import com.google.escapevelocity.TokenNode.MacroDefinitionTokenNode; +import com.google.escapevelocity.TokenNode.NestedTokenNode; +import java.util.Map; +import java.util.Set; +import java.util.TreeMap; + +/** + * The second phase of parsing. See {@link Parser#parse()} for a description of the phases and why + * we need them. + * + * @author emcmanus@google.com (Éamonn McManus) + */ +class Reparser { + private static final ImmutableSet<Class<? extends TokenNode>> END_SET = + ImmutableSet.<Class<? extends TokenNode>>of(EndTokenNode.class); + private static final ImmutableSet<Class<? extends TokenNode>> EOF_SET = + ImmutableSet.<Class<? extends TokenNode>>of(EofNode.class); + private static final ImmutableSet<Class<? extends TokenNode>> ELSE_ELSE_IF_END_SET = + ImmutableSet.<Class<? extends TokenNode>>of( + ElseTokenNode.class, ElseIfTokenNode.class, EndTokenNode.class); + + /** + * The nodes that make up the input sequence. Nodes are removed one by one from this list as + * parsing proceeds. At any time, {@link #currentNode} is the node being examined. + */ + private final ImmutableList<Node> nodes; + + /** + * The index of the node we are currently looking at while parsing. + */ + private int nodeIndex; + + /** + * Macros are removed from the input as they are found. They do not appear in the output parse + * tree. Macro definitions are not executed in place but are all applied before template rendering + * starts. This means that a macro can be referenced before it is defined. + */ + private final Map<String, Macro> macros; + + Reparser(ImmutableList<Node> nodes) { + this(nodes, new TreeMap<String, Macro>()); + } + + private Reparser(ImmutableList<Node> nodes, Map<String, Macro> macros) { + this.nodes = removeSpaceBeforeSet(nodes); + this.nodeIndex = 0; + this.macros = macros; + } + + Template reparse() { + Node root = reparseNodes(); + linkMacroCalls(); + return new Template(root); + } + + private Node reparseNodes() { + return parseTo(EOF_SET, new EofNode((String) null, 1)); + } + + /** + * Returns a copy of the given list where spaces have been moved where appropriate after {@code + * #set}. This hack is needed to match what appears to be special treatment in Apache Velocity of + * spaces before {@code #set} directives. If you have <i>thing</i> <i>whitespace</i> {@code #set}, + * then the whitespace is deleted if the <i>thing</i> is a comment ({@code ##...\n}); a reference + * ({@code $x} or {@code $x.foo} etc); a macro definition; or another {@code #set}. + */ + private static ImmutableList<Node> removeSpaceBeforeSet(ImmutableList<Node> nodes) { + assert nodes.get(nodes.size() - 1) instanceof EofNode : nodes.get(nodes.size() - 1); + // Since the last node is EofNode, the i + 1 and i + 2 accesses below are safe. + ImmutableList.Builder<Node> newNodes = ImmutableList.builder(); + for (int i = 0; i < nodes.size(); i++) { + Node nodeI = nodes.get(i); + newNodes.add(nodeI); + if (shouldDeleteSpaceBetweenThisAndSet(nodeI) + && isWhitespaceLiteral(nodes.get(i + 1)) + && nodes.get(i + 2) instanceof SetNode) { + // Skip the space. + i++; + } + } + return newNodes.build(); + } + + private static boolean shouldDeleteSpaceBetweenThisAndSet(Node node) { + return node instanceof CommentTokenNode + || node instanceof ReferenceNode + || node instanceof SetNode + || node instanceof MacroDefinitionTokenNode; + } + + private static boolean isWhitespaceLiteral(Node node) { + if (node instanceof ConstantExpressionNode) { + Object constant = node.evaluate(null); + if (constant instanceof String) { + String s = (String) constant; + int i = 0; + while (i < s.length()) { + int c = s.codePointAt(i); + if (!Character.isWhitespace(c)) { + return false; + } + i += Character.charCount(c); + } + return true; + } + } + return false; + } + + /** + * Parse subtrees until one of the token types in {@code stopSet} is encountered. + * If this is the top level, {@code stopSet} will include {@link EofNode} so parsing will stop + * when it reaches the end of the input. Otherwise, if an {@code EofNode} is encountered it is an + * error because we have something like {@code #if} without {@code #end}. + * + * @param stopSet the kinds of tokens that will stop the parse. For example, if we are parsing + * after an {@code #if}, we will stop at any of {@code #else}, {@code #elseif}, + * or {@code #end}. + * @param forWhat the token that triggered this call, for example the {@code #if} whose + * {@code #end} etc we are looking for. + * + * @return a Node that is the concatenation of the parsed subtrees + */ + private Node parseTo(Set<Class<? extends TokenNode>> stopSet, TokenNode forWhat) { + ImmutableList.Builder<Node> nodeList = ImmutableList.builder(); + while (true) { + Node currentNode = currentNode(); + if (stopSet.contains(currentNode.getClass())) { + break; + } + if (currentNode instanceof EofNode) { + throw new ParseException( + "Reached end of file while parsing " + forWhat.name(), + forWhat.resourceName, + forWhat.lineNumber); + } + Node parsed; + if (currentNode instanceof TokenNode) { + parsed = parseTokenNode(); + } else { + parsed = currentNode; + nextNode(); + } + nodeList.add(parsed); + } + return Node.cons(forWhat.resourceName, forWhat.lineNumber, nodeList.build()); + } + + private Node currentNode() { + return nodes.get(nodeIndex); + } + + private Node nextNode() { + Node currentNode = currentNode(); + if (currentNode instanceof EofNode) { + return currentNode; + } else { + nodeIndex++; + return currentNode(); + } + } + + private Node parseTokenNode() { + TokenNode tokenNode = (TokenNode) currentNode(); + nextNode(); + if (tokenNode instanceof CommentTokenNode) { + return emptyNode(tokenNode.resourceName, tokenNode.lineNumber); + } else if (tokenNode instanceof IfTokenNode) { + return parseIfOrElseIf((IfTokenNode) tokenNode); + } else if (tokenNode instanceof ForEachTokenNode) { + return parseForEach((ForEachTokenNode) tokenNode); + } else if (tokenNode instanceof NestedTokenNode) { + return parseNested((NestedTokenNode) tokenNode); + } else if (tokenNode instanceof MacroDefinitionTokenNode) { + return parseMacroDefinition((MacroDefinitionTokenNode) tokenNode); + } else { + throw new IllegalArgumentException( + "Unexpected token: " + tokenNode.name() + " on line " + tokenNode.lineNumber); + } + } + + private Node parseForEach(ForEachTokenNode forEach) { + Node body = parseTo(END_SET, forEach); + nextNode(); // Skip #end + return new ForEachNode( + forEach.resourceName, forEach.lineNumber, forEach.var, forEach.collection, body); + } + + private Node parseIfOrElseIf(IfOrElseIfTokenNode ifOrElseIf) { + Node truePart = parseTo(ELSE_ELSE_IF_END_SET, ifOrElseIf); + Node falsePart; + Node token = currentNode(); + nextNode(); // Skip #else or #elseif (cond) or #end. + if (token instanceof EndTokenNode) { + falsePart = emptyNode(token.resourceName, token.lineNumber); + } else if (token instanceof ElseTokenNode) { + falsePart = parseTo(END_SET, ifOrElseIf); + nextNode(); // Skip #end + } else if (token instanceof ElseIfTokenNode) { + // We've seen #if (condition1) ... #elseif (condition2). currentToken is the first token + // after (condition2). We pretend that we've just seen #if (condition2) and parse out + // the remainder (which might have further #elseif and final #else). Then we pretend that + // we actually saw #if (condition1) ... #else #if (condition2) ...remainder ... #end #end. + falsePart = parseIfOrElseIf((ElseIfTokenNode) token); + } else { + throw new AssertionError(currentNode()); + } + return new IfNode( + ifOrElseIf.resourceName, ifOrElseIf.lineNumber, ifOrElseIf.condition, truePart, falsePart); + } + + // This is a #parse("foo.vm") directive. We've already done the first phase of parsing on the + // contents of foo.vm. Now we need to do the second phase, and insert the result into the + // reparsed nodes. We can call Reparser recursively, but we must ensure that any macros found + // are added to the containing Reparser's macro definitions. + private Node parseNested(NestedTokenNode nested) { + Reparser reparser = new Reparser(nested.nodes, this.macros); + return reparser.reparseNodes(); + } + + private Node parseMacroDefinition(MacroDefinitionTokenNode macroDefinition) { + Node body = parseTo(END_SET, macroDefinition); + nextNode(); // Skip #end + if (!macros.containsKey(macroDefinition.name)) { + Macro macro = new Macro( + macroDefinition.lineNumber, macroDefinition.name, macroDefinition.parameterNames, body); + macros.put(macroDefinition.name, macro); + } + return emptyNode(macroDefinition.resourceName, macroDefinition.lineNumber); + } + + private void linkMacroCalls() { + for (Node node : nodes) { + if (node instanceof MacroCallNode) { + linkMacroCall((MacroCallNode) node); + } + } + } + + private void linkMacroCall(MacroCallNode macroCall) { + Macro macro = macros.get(macroCall.name()); + if (macro == null) { + throw new ParseException( + "#" + macroCall.name() + + " is neither a standard directive nor a macro that has been defined", + macroCall.resourceName, + macroCall.lineNumber); + } + if (macro.parameterCount() != macroCall.argumentCount()) { + throw new ParseException( + "Wrong number of arguments to #" + macroCall.name() + + ": expected " + macro.parameterCount() + + ", got " + macroCall.argumentCount(), + macroCall.resourceName, + macroCall.lineNumber); + } + macroCall.setMacro(macro); + } +} |