| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 freemarker.core; |
| |
| import java.util.List; |
| |
| import freemarker.template.TemplateException; |
| import freemarker.template.TemplateModel; |
| |
| /** |
| * A local lambada expression is a lambda expression that creates a function that can only be called from the same |
| * context where it was created, and thus it doesn't need closure support. As of this writing (2019-02), this is the |
| * only kind of lambda expression supported, as supporting closures would add overhead to many basic operations, while |
| * local lambdas are "good enough" for the main use cases in templates (for filtering/transforming lists). Also, |
| * closures can be quite confusing when the lambda expression refers to variables that are not effectively final, |
| * such as a loop variable. So that's yet another issue to address if we go for less restricted lambdas. |
| */ |
| final class LocalLambdaExpression extends Expression { |
| |
| private final LambdaParameterList lho; |
| private final Expression rho; |
| |
| LocalLambdaExpression(LambdaParameterList lho, Expression rho) { |
| this.lho = lho; |
| this.rho = rho; |
| } |
| |
| @Override |
| public String getCanonicalForm() { |
| return lho.getCanonicalForm() + " -> " + rho.getCanonicalForm(); |
| } |
| |
| @Override |
| String getNodeTypeSymbol() { |
| return "->"; |
| } |
| |
| @Override |
| TemplateModel _eval(Environment env) throws TemplateException { |
| throw new TemplateException("Can't get lambda expression as a value: Lambdas currently can only be used on a " + |
| "few special places.", |
| env); |
| } |
| |
| /** |
| * Call the function defined by the lambda expression; overload specialized for 1 argument, the most common case. |
| */ |
| TemplateModel invokeLambdaDefinedFunction(TemplateModel argValue, Environment env) throws TemplateException { |
| return env.evaluateWithNewLocal(rho, lho.getParameters().get(0).getName(), |
| argValue != null ? argValue : TemplateNullModel.INSTANCE); |
| } |
| |
| @Override |
| boolean isLiteral() { |
| // As we don't support true lambdas, they can't be evaluted in parse time. |
| return false; |
| } |
| |
| @Override |
| protected Expression deepCloneWithIdentifierReplaced_inner( |
| String replacedIdentifier, Expression replacement, ReplacemenetState replacementState) { |
| for (Identifier parameter : lho.getParameters()) { |
| if (parameter.getName().equals(replacedIdentifier)) { |
| // As Expression.deepCloneWithIdentifierReplaced was exposed to users back then, now we can't add |
| // "throws ParseException" to this, therefore, we use UncheckedParseException as a workaround. |
| throw new UncheckedParseException(new ParseException( |
| "Escape placeholder (" + replacedIdentifier + ") can't be used in the " + |
| "parameter list of a lambda expressions.", this)); |
| } |
| } |
| |
| return new LocalLambdaExpression( |
| lho, |
| rho.deepCloneWithIdentifierReplaced(replacedIdentifier, replacement, replacementState)); |
| } |
| |
| @Override |
| int getParameterCount() { |
| return lho.getParameters().size() + 1; |
| } |
| |
| @Override |
| Object getParameterValue(int idx) { |
| int paramCount = getParameterCount(); |
| if (idx < paramCount - 1) { |
| return lho.getParameters().get(idx); |
| } else if (idx == paramCount - 1) { |
| return rho; |
| } else { |
| throw new IndexOutOfBoundsException(); |
| } |
| } |
| |
| @Override |
| ParameterRole getParameterRole(int idx) { |
| int paramCount = getParameterCount(); |
| if (idx < paramCount - 1) { |
| return ParameterRole.ARGUMENT_NAME; |
| } else if (idx == paramCount - 1) { |
| return ParameterRole.VALUE; |
| } else { |
| throw new IndexOutOfBoundsException(); |
| } |
| } |
| |
| LambdaParameterList getLambdaParameterList() { |
| return lho; |
| } |
| |
| /** The left side of the `->`. */ |
| static class LambdaParameterList { |
| private final Token openingParenthesis; |
| private final Token closingParenthesis; |
| private final List<Identifier> parameters; |
| |
| public LambdaParameterList(Token openingParenthesis, List<Identifier> parameters, Token closingParenthesis) { |
| this.openingParenthesis = openingParenthesis; |
| this.closingParenthesis = closingParenthesis; |
| this.parameters = parameters; |
| } |
| |
| /** Maybe {@code null} */ |
| public Token getOpeningParenthesis() { |
| return openingParenthesis; |
| } |
| |
| /** Maybe {@code null} */ |
| public Token getClosingParenthesis() { |
| return closingParenthesis; |
| } |
| |
| public List<Identifier> getParameters() { |
| return parameters; |
| } |
| |
| public String getCanonicalForm() { |
| if (parameters.size() == 1) { |
| return parameters.get(0).getCanonicalForm(); |
| } else { |
| StringBuilder sb = new StringBuilder(); |
| sb.append('('); |
| for (int i = 0; i < parameters.size(); i++) { |
| if (i != 0) { |
| sb.append(", "); |
| } |
| Identifier parameter = parameters.get(i); |
| sb.append(parameter.getCanonicalForm()); |
| } |
| sb.append(')'); |
| return sb.toString(); |
| } |
| } |
| } |
| |
| } |