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repl.ts
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repl.ts
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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
import { close } from "./files";
import { exit } from "./os";
import { window } from "./window";
import { core } from "./core";
import { formatError } from "./format_error";
import { stringifyArgs } from "./console";
import * as dispatch from "./dispatch";
import { sendSync, sendAsync } from "./dispatch_json";
/**
* REPL logging.
* In favor of console.log to avoid unwanted indentation
*/
function replLog(...args: unknown[]): void {
core.print(stringifyArgs(args) + "\n");
}
/**
* REPL logging for errors.
* In favor of console.error to avoid unwanted indentation
*/
function replError(...args: unknown[]): void {
core.print(stringifyArgs(args) + "\n", true);
}
const helpMsg = [
"_ Get last evaluation result",
"_error Get last thrown error",
"exit Exit the REPL",
"help Print this help message"
].join("\n");
const replCommands = {
exit: {
get(): void {
exit(0);
}
},
help: {
get(): string {
return helpMsg;
}
}
};
function startRepl(historyFile: string): number {
return sendSync(dispatch.OP_REPL_START, { historyFile });
}
// @internal
export async function readline(rid: number, prompt: string): Promise<string> {
return sendAsync(dispatch.OP_REPL_READLINE, { rid, prompt });
}
// Error messages that allow users to continue input
// instead of throwing an error to REPL
// ref: https://github.com/v8/v8/blob/master/src/message-template.h
// TODO(kevinkassimo): this list might not be comprehensive
const recoverableErrorMessages = [
"Unexpected end of input", // { or [ or (
"Missing initializer in const declaration", // const a
"Missing catch or finally after try", // try {}
"missing ) after argument list", // console.log(1
"Unterminated template literal" // `template
// TODO(kevinkassimo): need a parser to handling errors such as:
// "Missing } in template expression" // `${ or `${ a 123 }`
];
function isRecoverableError(e: Error): boolean {
return recoverableErrorMessages.includes(e.message);
}
// eslint-disable-next-line @typescript-eslint/no-explicit-any
type Value = any;
let lastEvalResult: Value = undefined;
let lastThrownError: Value = undefined;
// Evaluate code.
// Returns true if code is consumed (no error/irrecoverable error).
// Returns false if error is recoverable
function evaluate(code: string): boolean {
const [result, errInfo] = core.evalContext(code);
if (!errInfo) {
lastEvalResult = result;
replLog(result);
} else if (errInfo.isCompileError && isRecoverableError(errInfo.thrown)) {
// Recoverable compiler error
return false; // don't consume code.
} else {
lastThrownError = errInfo.thrown;
if (errInfo.isNativeError) {
const formattedError = formatError(
core.errorToJSON(errInfo.thrown as Error)
);
replError(formattedError);
} else {
replError("Thrown:", errInfo.thrown);
}
}
return true;
}
// @internal
export async function replLoop(): Promise<void> {
Object.defineProperties(window, replCommands);
const historyFile = "deno_history.txt";
const rid = startRepl(historyFile);
const quitRepl = (exitCode: number): void => {
// Special handling in case user calls deno.close(3).
try {
close(rid); // close signals Drop on REPL and saves history.
} catch {}
exit(exitCode);
};
// Configure window._ to give the last evaluation result.
Object.defineProperty(window, "_", {
configurable: true,
get: (): Value => lastEvalResult,
set: (value: Value): Value => {
Object.defineProperty(window, "_", {
value: value,
writable: true,
enumerable: true,
configurable: true
});
console.log("Last evaluation result is no longer saved to _.");
}
});
// Configure window._error to give the last thrown error.
Object.defineProperty(window, "_error", {
configurable: true,
get: (): Value => lastThrownError,
set: (value: Value): Value => {
Object.defineProperty(window, "_error", {
value: value,
writable: true,
enumerable: true,
configurable: true
});
console.log("Last thrown error is no longer saved to _error.");
}
});
while (true) {
let code = "";
// Top level read
try {
code = await readline(rid, "> ");
if (code.trim() === "") {
continue;
}
} catch (err) {
if (err.message === "EOF") {
quitRepl(0);
} else {
// If interrupted, don't print error.
if (err.message !== "Interrupted") {
// e.g. this happens when we have deno.close(3).
// We want to display the problem.
const formattedError = formatError(core.errorToJSON(err));
replError(formattedError);
}
// Quit REPL anyways.
quitRepl(1);
}
}
// Start continued read
while (!evaluate(code)) {
code += "\n";
try {
code += await readline(rid, " ");
} catch (err) {
// If interrupted on continued read,
// abort this read instead of quitting.
if (err.message === "Interrupted") {
break;
} else if (err.message === "EOF") {
quitRepl(0);
} else {
// e.g. this happens when we have deno.close(3).
// We want to display the problem.
const formattedError = formatError(core.errorToJSON(err));
replError(formattedError);
quitRepl(1);
}
}
}
}
}