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// 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.collect.ImmutableList;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
/** A helper class for calling Skylark functions from Java. */
@AutoCodec
public class SkylarkCallbackFunction {
private final BaseFunction callback;
private final FuncallExpression ast;
private final SkylarkSemantics skylarkSemantics;
public SkylarkCallbackFunction(
BaseFunction callback, FuncallExpression ast, SkylarkSemantics skylarkSemantics) {
this.callback = callback;
this.ast = ast;
this.skylarkSemantics = skylarkSemantics;
}
public ImmutableList<String> getParameterNames() {
return callback.signature.getSignature().getNames();
}
public Object call(EventHandler eventHandler, ClassObject ctx, Object... arguments)
throws EvalException, InterruptedException {
try (Mutability mutability = Mutability.create("callback %s", callback)) {
Environment env =
Environment.builder(mutability)
.setSemantics(skylarkSemantics)
.setEventHandler(eventHandler)
.build();
return callback.call(buildArgumentList(ctx, arguments), null, ast, env);
} catch (ClassCastException | IllegalArgumentException e) {
throw new EvalException(ast.getLocation(), e.getMessage());
}
}
/**
* Creates a list of actual arguments that contains the given arguments and all attribute values
* required from the specified context.
*/
private ImmutableList<Object> buildArgumentList(ClassObject ctx, Object... arguments)
throws EvalException {
ImmutableList.Builder<Object> builder = ImmutableList.builder();
ImmutableList<String> names = getParameterNames();
int requiredParameters = names.size() - arguments.length;
for (int pos = 0; pos < requiredParameters; ++pos) {
String name = names.get(pos);
Object value = ctx.getValue(name);
if (value == null) {
throw new IllegalArgumentException(ctx.getErrorMessageForUnknownField(name));
}
builder.add(value);
}
return builder.add(arguments).build();
}
}
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