| // 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 net.starlark.java.cmd; |
| |
| import static java.nio.charset.StandardCharsets.UTF_8; |
| |
| import java.io.BufferedReader; |
| import java.io.FileOutputStream; |
| import java.io.IOException; |
| import java.io.InputStreamReader; |
| import java.time.Duration; |
| import java.util.List; |
| import javax.annotation.Nullable; |
| import net.starlark.java.eval.EvalException; |
| import net.starlark.java.eval.Module; |
| import net.starlark.java.eval.Mutability; |
| import net.starlark.java.eval.Starlark; |
| import net.starlark.java.eval.StarlarkSemantics; |
| import net.starlark.java.eval.StarlarkThread; |
| import net.starlark.java.syntax.FileOptions; |
| import net.starlark.java.syntax.ParserInput; |
| import net.starlark.java.syntax.StarlarkFile; |
| import net.starlark.java.syntax.Statement; |
| import net.starlark.java.syntax.SyntaxError; |
| |
| /** |
| * Main is a standalone interpreter for the core Starlark language. It does not yet support load |
| * statements. |
| * |
| * <p>The sad class name is due to the linting tool, which forbids lowercase "starlark", and Java's |
| * lack of renaming imports, which makes the name "Starlark" impractical due to conflicts with |
| * eval.Starlark. |
| */ |
| class Main { |
| private static final String START_PROMPT = ">> "; |
| private static final String CONTINUATION_PROMPT = ".. "; |
| |
| private static final BufferedReader reader = |
| new BufferedReader(new InputStreamReader(System.in, UTF_8)); |
| private static final StarlarkThread thread; |
| private static final Module module = Module.create(); |
| |
| // Variables bound by load in one REPL chunk are visible in the next. |
| private static final FileOptions OPTIONS = |
| FileOptions.DEFAULT.toBuilder().allowToplevelRebinding(true).loadBindsGlobally(true).build(); |
| |
| static { |
| Mutability mu = Mutability.create("interpreter"); |
| thread = new StarlarkThread(mu, StarlarkSemantics.DEFAULT); |
| thread.setPrintHandler((th, msg) -> System.out.println(msg)); |
| } |
| |
| // Prompts the user for a chunk of input, and returns it. |
| @Nullable |
| private static String prompt() { |
| StringBuilder input = new StringBuilder(); |
| System.out.print(START_PROMPT); |
| try { |
| String lineSeparator = ""; |
| loop: |
| while (true) { |
| String line = reader.readLine(); |
| if (line == null) { |
| return null; |
| } |
| if (line.isEmpty()) { |
| break loop; // a blank line ends the chunk |
| } |
| input.append(lineSeparator).append(line); |
| |
| // Read lines until input produces valid statements, unless the last is if/def/for, |
| // which can be multiline, in which case we must wait for a blank 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. |
| StarlarkFile file = StarlarkFile.parse(ParserInput.fromString(input.toString(), "<stdin>")); |
| if (file.ok()) { |
| List<Statement> stmts = file.getStatements(); |
| if (!stmts.isEmpty()) { |
| Statement last = stmts.get(stmts.size() - 1); |
| switch (last.kind()) { |
| case IF: |
| case DEF: |
| case FOR: |
| break; // keep going until blank line |
| default: |
| break loop; |
| } |
| } |
| } |
| |
| lineSeparator = "\n"; |
| System.out.print(CONTINUATION_PROMPT); |
| } |
| } catch (IOException e) { |
| System.err.format("Error reading line: %s\n", e); |
| return null; |
| } |
| return input.toString(); |
| } |
| |
| /** Provide a REPL evaluating Starlark code. */ |
| @SuppressWarnings("CatchAndPrintStackTrace") |
| private static void readEvalPrintLoop() { |
| module.setDocumentation("<REPL>"); // Do not retrieve a module docstring from REPL input. |
| System.err.println("Welcome to Starlark (java.starlark.net)"); |
| String line; |
| |
| while ((line = prompt()) != null) { |
| ParserInput input = ParserInput.fromString(line, "<stdin>"); |
| try { |
| Object result = Starlark.execFile(input, OPTIONS, module, thread); |
| if (result != Starlark.NONE) { |
| System.out.println(Starlark.repr(result)); |
| } |
| } catch (SyntaxError.Exception ex) { |
| for (SyntaxError error : ex.errors()) { |
| System.err.println(error); |
| } |
| } catch (EvalException ex) { |
| // TODO(adonovan): provide a SourceReader. Requires that we buffer the |
| // entire history so that line numbers don't reset in each chunk. |
| System.err.println(ex.getMessageWithStack()); |
| } catch (InterruptedException ex) { |
| System.err.println("Interrupted"); |
| } |
| } |
| } |
| |
| /** Execute a Starlark file. */ |
| private static int execute(ParserInput input) { |
| try { |
| Starlark.execFile(input, OPTIONS, module, thread); |
| return 0; |
| } catch (SyntaxError.Exception ex) { |
| for (SyntaxError error : ex.errors()) { |
| System.err.println(error); |
| } |
| return 1; |
| } catch (EvalException ex) { |
| System.err.println(ex.getMessageWithStack()); |
| return 1; |
| } catch (InterruptedException e) { |
| System.err.println("Interrupted"); |
| return 1; |
| } |
| } |
| |
| public static void main(String[] args) throws IOException { |
| String file = null; |
| String cmd = null; |
| String cpuprofile = null; |
| |
| // parse flags |
| int i; |
| for (i = 0; i < args.length; i++) { |
| if (!args[i].startsWith("-")) { |
| break; |
| } |
| if (args[i].equals("--")) { |
| i++; |
| break; |
| } |
| if (args[i].equals("-c")) { |
| if (i + 1 == args.length) { |
| throw new IOException("-c <cmd> flag needs an argument"); |
| } |
| cmd = args[++i]; |
| } else if (args[i].equals("-cpuprofile")) { |
| if (i + 1 == args.length) { |
| throw new IOException("-cpuprofile <file> flag needs an argument"); |
| } |
| cpuprofile = args[++i]; |
| } else { |
| throw new IOException("unknown flag: " + args[i]); |
| } |
| } |
| // positional arguments |
| if (i < args.length) { |
| if (i + 1 < args.length) { |
| throw new IOException("too many positional arguments"); |
| } |
| file = args[i]; |
| } |
| |
| if (cpuprofile != null) { |
| FileOutputStream out = new FileOutputStream(cpuprofile); |
| Starlark.startCpuProfile(out, Duration.ofMillis(10)); |
| } |
| |
| int exit; |
| if (file == null) { |
| if (cmd != null) { |
| exit = execute(ParserInput.fromString(cmd, "<command-line>")); |
| } else { |
| readEvalPrintLoop(); |
| exit = 0; |
| } |
| } else if (cmd == null) { |
| try { |
| exit = execute(ParserInput.readFile(file)); |
| } catch (IOException e) { |
| // This results in such lame error messages as: |
| // "Error reading a.star: java.nio.file.NoSuchFileException: a.star" |
| System.err.format("Error reading %s: %s\n", file, e); |
| exit = 1; |
| } |
| } else { |
| System.err.println("usage: Starlark [-cpuprofile file] [-c cmd | file]"); |
| exit = 1; |
| } |
| |
| if (cpuprofile != null) { |
| Starlark.stopCpuProfile(); |
| } |
| |
| System.exit(exit); |
| } |
| } |