| // Copyright 2014 The Bazel Authors. All rights reserved. |
| // |
| // 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.devtools.build.lib.syntax; |
| |
| import com.google.common.base.Preconditions; |
| import com.google.devtools.build.lib.events.Event; |
| import com.google.devtools.build.lib.events.EventHandler; |
| import com.google.devtools.build.lib.events.Location; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Set; |
| import javax.annotation.Nullable; |
| |
| /** A class for doing static checks on files, before evaluating them. */ |
| public final class ValidationEnvironment extends SyntaxTreeVisitor { |
| |
| private static class Block { |
| private final Set<String> variables = new HashSet<>(); |
| private final Set<String> readOnlyVariables = new HashSet<>(); |
| @Nullable private final Block parent; |
| |
| Block(@Nullable Block parent) { |
| this.parent = parent; |
| } |
| } |
| |
| /** |
| * We use an unchecked exception around EvalException because the SyntaxTreeVisitor doesn't let |
| * visit methods throw checked exceptions. We might change that later. |
| */ |
| private static class ValidationException extends RuntimeException { |
| EvalException exception; |
| |
| ValidationException(EvalException e) { |
| exception = e; |
| } |
| |
| ValidationException(Location location, String message, String url) { |
| exception = new EvalException(location, message, url); |
| } |
| |
| ValidationException(Location location, String message) { |
| exception = new EvalException(location, message); |
| } |
| } |
| |
| private final SkylarkSemantics semantics; |
| private Block block; |
| private int loopCount; |
| |
| /** Create a ValidationEnvironment for a given global Environment. */ |
| ValidationEnvironment(Environment env) { |
| Preconditions.checkArgument(env.isGlobal()); |
| block = new Block(null); |
| Set<String> builtinVariables = env.getVariableNames(); |
| block.variables.addAll(builtinVariables); |
| block.readOnlyVariables.addAll(builtinVariables); |
| semantics = env.getSemantics(); |
| } |
| |
| @Override |
| public void visit(LoadStatement node) { |
| for (Identifier symbol : node.getSymbols()) { |
| declare(symbol.getName(), node.getLocation()); |
| } |
| } |
| |
| @Override |
| public void visit(Identifier node) { |
| if (!hasSymbolInEnvironment(node.getName())) { |
| throw new ValidationException(node.createInvalidIdentifierException(getAllSymbols())); |
| } |
| } |
| |
| private void validateLValue(Location loc, Expression expr) { |
| if (expr instanceof Identifier) { |
| declare(((Identifier) expr).getName(), loc); |
| } else if (expr instanceof IndexExpression) { |
| visit(expr); |
| } else if (expr instanceof ListLiteral) { |
| for (Expression e : ((ListLiteral) expr).getElements()) { |
| validateLValue(loc, e); |
| } |
| } else { |
| throw new ValidationException(loc, "cannot assign to '" + expr + "'"); |
| } |
| } |
| |
| @Override |
| public void visit(LValue node) { |
| validateLValue(node.getLocation(), node.getExpression()); |
| } |
| |
| @Override |
| public void visit(ReturnStatement node) { |
| if (isTopLevel()) { |
| throw new ValidationException( |
| node.getLocation(), "return statements must be inside a function"); |
| } |
| super.visit(node); |
| } |
| |
| @Override |
| public void visit(ForStatement node) { |
| loopCount++; |
| super.visit(node); |
| Preconditions.checkState(loopCount > 0); |
| loopCount--; |
| } |
| |
| @Override |
| public void visit(FlowStatement node) { |
| if (loopCount <= 0) { |
| throw new ValidationException( |
| node.getLocation(), node.getKind().getName() + " statement must be inside a for loop"); |
| } |
| super.visit(node); |
| } |
| |
| @Override |
| public void visit(DotExpression node) { |
| visit(node.getObject()); |
| // Do not visit the field. |
| } |
| |
| @Override |
| public void visit(AbstractComprehension node) { |
| if (semantics.incompatibleComprehensionVariablesDoNotLeak()) { |
| openBlock(); |
| super.visit(node); |
| closeBlock(); |
| } else { |
| super.visit(node); |
| } |
| } |
| |
| @Override |
| public void visit(FunctionDefStatement node) { |
| for (Parameter<Expression, Expression> param : node.getParameters()) { |
| if (param.isOptional()) { |
| visit(param.getDefaultValue()); |
| } |
| } |
| openBlock(); |
| for (Parameter<Expression, Expression> param : node.getParameters()) { |
| if (param.hasName()) { |
| declare(param.getName(), param.getLocation()); |
| } |
| } |
| visitAll(node.getStatements()); |
| closeBlock(); |
| } |
| |
| @Override |
| public void visit(IfStatement node) { |
| if (semantics.incompatibleDisallowToplevelIfStatement() && isTopLevel()) { |
| throw new ValidationException( |
| node.getLocation(), |
| "if statements are not allowed at the top level. You may move it inside a function " |
| + "or use an if expression (x if condition else y). " |
| + "Use --incompatible_disallow_toplevel_if_statement=false to temporarily disable " |
| + "this check."); |
| } |
| super.visit(node); |
| } |
| |
| @Override |
| public void visit(AugmentedAssignmentStatement node) { |
| if (node.getLValue().getExpression() instanceof ListLiteral) { |
| throw new ValidationException( |
| node.getLocation(), "cannot perform augmented assignment on a list or tuple expression"); |
| } |
| // Other bad cases are handled when visiting the LValue node. |
| super.visit(node); |
| } |
| |
| /** Returns true if the current block is the top level i.e. has no parent. */ |
| private boolean isTopLevel() { |
| return block.parent == null; |
| } |
| |
| /** Declare a variable and add it to the environment. */ |
| private void declare(String varname, Location location) { |
| if (block.readOnlyVariables.contains(varname)) { |
| throw new ValidationException( |
| location, |
| String.format("Variable %s is read only", varname), |
| "https://bazel.build/versions/master/docs/skylark/errors/read-only-variable.html"); |
| } |
| if (isTopLevel()) { // top-level values are immutable |
| block.readOnlyVariables.add(varname); |
| } |
| block.variables.add(varname); |
| } |
| |
| /** Returns true if the symbol exists in the validation environment (or a parent). */ |
| private boolean hasSymbolInEnvironment(String varname) { |
| for (Block b = block; b != null; b = b.parent) { |
| if (b.variables.contains(varname)) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** Returns the set of all accessible symbols (both local and global) */ |
| private Set<String> getAllSymbols() { |
| Set<String> all = new HashSet<>(); |
| for (Block b = block; b != null; b = b.parent) { |
| all.addAll(b.variables); |
| } |
| return all; |
| } |
| |
| /** Throws ValidationException if a load() appears after another kind of statement. */ |
| private static void checkLoadAfterStatement(List<Statement> statements) { |
| Location firstStatement = null; |
| |
| for (Statement statement : statements) { |
| // Ignore string literals (e.g. docstrings). |
| if (statement instanceof ExpressionStatement |
| && ((ExpressionStatement) statement).getExpression() instanceof StringLiteral) { |
| continue; |
| } |
| |
| if (statement instanceof LoadStatement) { |
| if (firstStatement == null) { |
| continue; |
| } |
| throw new ValidationException( |
| statement.getLocation(), |
| "load() statements must be called before any other statement. " |
| + "First non-load() statement appears at " |
| + firstStatement |
| + ". Use --incompatible_bzl_disallow_load_after_statement=false to temporarily " |
| + "disable this check."); |
| } |
| |
| if (firstStatement == null) { |
| firstStatement = statement.getLocation(); |
| } |
| } |
| } |
| |
| /** Validates the AST and runs static checks. */ |
| private void validateAst(List<Statement> statements) { |
| // Check that load() statements are on top. |
| if (semantics.incompatibleBzlDisallowLoadAfterStatement()) { |
| checkLoadAfterStatement(statements); |
| } |
| |
| // Add every function in the environment before validating. This is |
| // necessary because functions may call other functions defined |
| // later in the file. |
| for (Statement statement : statements) { |
| if (statement instanceof FunctionDefStatement) { |
| FunctionDefStatement fct = (FunctionDefStatement) statement; |
| declare(fct.getIdentifier().getName(), fct.getLocation()); |
| } |
| } |
| |
| this.visitAll(statements); |
| } |
| |
| public static void validateAst(Environment env, List<Statement> statements) throws EvalException { |
| try { |
| ValidationEnvironment venv = new ValidationEnvironment(env); |
| venv.validateAst(statements); |
| // Check that no closeBlock was forgotten. |
| Preconditions.checkState(venv.block.parent == null); |
| } catch (ValidationException e) { |
| throw e.exception; |
| } |
| } |
| |
| public static boolean validateAst( |
| Environment env, List<Statement> statements, EventHandler eventHandler) { |
| try { |
| validateAst(env, statements); |
| return true; |
| } catch (EvalException e) { |
| if (!e.isDueToIncompleteAST()) { |
| eventHandler.handle(Event.error(e.getLocation(), e.getMessage())); |
| } |
| return false; |
| } |
| } |
| |
| /** Open a new lexical block that will contain the future declarations. */ |
| private void openBlock() { |
| block = new Block(block); |
| } |
| |
| /** Close a lexical block (and lose all declarations it contained). */ |
| private void closeBlock() { |
| block = Preconditions.checkNotNull(block.parent); |
| } |
| |
| /** |
| * Checks that the AST is using the restricted syntax. |
| * |
| * <p>Restricted syntax is used by Bazel BUILD files. It forbids function definitions, *args, and |
| * **kwargs. This creates a better separation between code and data. |
| */ |
| public static boolean checkBuildSyntax( |
| List<Statement> statements, final EventHandler eventHandler) { |
| // Wrap the boolean inside an array so that the inner class can modify it. |
| final boolean[] success = new boolean[] {true}; |
| // TODO(laurentlb): Merge with the visitor above when possible (i.e. when BUILD files use it). |
| SyntaxTreeVisitor checker = |
| new SyntaxTreeVisitor() { |
| @Override |
| public void visit(FuncallExpression node) { |
| for (Argument.Passed arg : node.getArguments()) { |
| if (arg.isStarStar()) { |
| eventHandler.handle( |
| Event.error( |
| node.getLocation(), "**kwargs arguments are not allowed in BUILD files")); |
| success[0] = false; |
| } else if (arg.isStar()) { |
| eventHandler.handle( |
| Event.error( |
| node.getLocation(), "*args arguments are not allowed in BUILD files")); |
| success[0] = false; |
| } |
| } |
| } |
| |
| @Override |
| public void visit(FunctionDefStatement node) { |
| eventHandler.handle( |
| Event.error( |
| node.getLocation(), |
| "syntax error at 'def': This is not supported in BUILD files. " |
| + "Move the block to a .bzl file and load it")); |
| success[0] = false; |
| } |
| }; |
| checker.visitAll(statements); |
| return success[0]; |
| } |
| } |