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// Copyright 2015 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.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.EventHandler;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
/**
* SkylarkShell is a standalone shell executing Skylark. This is intended for
* testing purposes and not for end-users. This is very limited (environment is
* almost empty), but it can be used to play with the language and reproduce
* bugs. Imports and includes are not supported.
*/
class SkylarkShell {
private static final String START_PROMPT = ">> ";
private static final String CONTINUATION_PROMPT = ".. ";
public static final EventHandler PRINT_HANDLER = new EventHandler() {
@Override
public void handle(Event event) {
System.out.println(event.getMessage());
}
};
private final BufferedReader reader = new BufferedReader(
new InputStreamReader(System.in, Charset.defaultCharset()));
private final Mutability mutability = Mutability.create("shell");
private final Environment env = Environment.builder(mutability)
.setSkylark().setGlobals(Environment.SKYLARK).setEventHandler(PRINT_HANDLER).build();
public String read() {
StringBuilder input = new StringBuilder();
System.out.print(START_PROMPT);
try {
while (true) {
String line = reader.readLine();
if (line == null) {
return null;
}
if (line.isEmpty()) {
return input.toString();
}
input.append("\n").append(line);
System.out.print(CONTINUATION_PROMPT);
}
} catch (IOException io) {
io.printStackTrace();
return null;
}
}
public void readEvalPrintLoop() {
String input;
while ((input = read()) != null) {
try {
Object result = env.eval(input);
if (result != null) {
System.out.println(Printer.repr(result));
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
new SkylarkShell().readEvalPrintLoop();
}
}
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