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// Copyright 2016 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.skylark;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.events.EventKind;
import com.google.devtools.build.lib.syntax.BuildFileAST;
import com.google.devtools.build.lib.syntax.Environment;
import com.google.devtools.build.lib.syntax.EvalException;
import com.google.devtools.build.lib.syntax.Mutability;
import com.google.devtools.build.lib.syntax.Printer;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
/**
* Skylark is a standalone skylark intepreter. The environment doesn't
* contain Bazel-specific functions and variables. Load statements are
* forbidden for the moment.
*/
class Skylark {
private static final String START_PROMPT = ">> ";
private static final String CONTINUATION_PROMPT = ".. ";
private static final EventHandler PRINT_HANDLER =
new EventHandler() {
@Override
public void handle(Event event) {
if (event.getKind() == EventKind.ERROR) {
System.err.println(event.getMessage());
} else {
System.out.println(event.getMessage());
}
}
};
private static final Charset CHARSET = StandardCharsets.ISO_8859_1;
private final BufferedReader reader =
new BufferedReader(new InputStreamReader(System.in, CHARSET));
private final Mutability mutability = Mutability.create("interpreter");
private final Environment env =
Environment.builder(mutability)
.useDefaultSemantics()
.setGlobals(Environment.DEFAULT_GLOBALS)
.setEventHandler(PRINT_HANDLER)
.build();
private String prompt() {
StringBuilder input = new StringBuilder();
System.out.print(START_PROMPT);
try {
String lineSeparator = "";
while (true) {
String line = reader.readLine();
if (line == null) {
return null;
}
if (line.isEmpty()) {
return input.toString();
}
input.append(lineSeparator).append(line);
lineSeparator = "\n";
System.out.print(CONTINUATION_PROMPT);
}
} catch (IOException io) {
io.printStackTrace();
return null;
}
}
/** Provide a REPL evaluating Skylark code. */
public void readEvalPrintLoop() {
String input;
while ((input = prompt()) != null) {
try {
Object result = BuildFileAST.eval(env, input);
if (result != null) {
System.out.println(Printer.repr(result));
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
/** Execute a Skylark file. */
public int execute(String path) {
String content;
try {
content = new String(Files.readAllBytes(Paths.get(path)), CHARSET);
BuildFileAST.eval(env, content);
return 0;
} catch (EvalException e) {
System.err.println(e.print());
return 1;
} catch (Exception e) {
e.printStackTrace(System.err);
return 1;
}
}
public static void main(String[] args) {
int ret = 0;
if (args.length == 0) {
new Skylark().readEvalPrintLoop();
} else if (args.length == 1) {
ret = new Skylark().execute(args[0]);
} else {
System.err.println("too many arguments");
ret = 1;
}
System.exit(ret);
}
}
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