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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.starlark;
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.EvalException;
import com.google.devtools.build.lib.syntax.EvalUtils;
import com.google.devtools.build.lib.syntax.Mutability;
import com.google.devtools.build.lib.syntax.ParserInput;
import com.google.devtools.build.lib.syntax.Printer;
import com.google.devtools.build.lib.syntax.StarlarkThread;
import com.google.devtools.build.lib.syntax.SyntaxError;
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;
/**
* Starlark is a standalone starlark intepreter. The environment doesn't
* contain Bazel-specific functions and variables. Load statements are
* forbidden for the moment.
*/
class Starlark {
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 StarlarkThread thread =
StarlarkThread.builder(mutability)
.useDefaultSemantics()
.setGlobals(StarlarkThread.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 Starlark code. */
@SuppressWarnings("CatchAndPrintStackTrace")
public void readEvalPrintLoop() {
String line;
// TODO(adonovan): parse a compound statement, like the Python and
// go.starlark.net REPLs. This requires a new grammar production, and
// integration with the lexer so that it consumes new
// lines only until the parse is complete.
while ((line = prompt()) != null) {
ParserInput input = ParserInput.fromLines(line);
try {
Object result = EvalUtils.execAndEvalOptionalFinalExpression(input, thread);
if (result != null) {
System.out.println(Printer.repr(result));
}
} catch (SyntaxError ex) {
for (Event ev : ex.errors()) {
System.err.println(ev);
}
} catch (EvalException ex) {
// TODO(adonovan): show Starlark (not Java) stack.
ex.printStackTrace();
} catch (InterruptedException ex) {
System.err.println("Interrupted");
}
}
}
/** Execute a Starlark file. */
public int executeFile(String path) {
String content;
try {
content = new String(Files.readAllBytes(Paths.get(path)), CHARSET);
return execute(content);
} catch (Exception e) {
e.printStackTrace();
return 1;
}
}
/** Execute a Starlark file. */
public int execute(String content) {
ParserInput input = ParserInput.create(content, null);
try {
EvalUtils.exec(input, thread);
return 0;
} catch (SyntaxError ex) {
for (Event ev : ex.errors()) {
System.err.println(ev);
}
return 1;
} 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 Starlark().readEvalPrintLoop();
} else if (args.length == 1 && !args[0].equals("-c")) {
ret = new Starlark().executeFile(args[0]);
} else if (args.length == 2 && args[0].equals("-c")) {
ret = new Starlark().execute(args[1]);
} else {
System.err.println("USAGE: Starlark [-c \"<cmdLineProgram>\" | <fileName>]");
ret = 1;
}
System.exit(ret);
}
}