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Extract subprocess management to a reusable module.
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// Copyright 2014 Selenium committers | ||
// Copyright 2014 Software Freedom Conservancy | ||
// | ||
// 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. | ||
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'use strict'; | ||
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var childProcess = require('child_process'); | ||
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var promise = require('..').promise; | ||
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/** | ||
* A hash with configuration options for an executed command. | ||
* <ul> | ||
* <li> | ||
* <li>{@code args} - Command line arguments. | ||
* <li>{@code env} - Command environment; will inherit from the current process | ||
* if missing. | ||
* <li>{@code stdio} - IO configuration for the spawned server process. For | ||
* more information, refer to the documentation of | ||
* {@code child_process.spawn}. | ||
* </ul> | ||
* | ||
* @typedef {{ | ||
* args: (!Array.<string>|undefined), | ||
* env: (!Object.<string, string>|undefined), | ||
* stdio: (string|!Array.<string|number|!Stream|null|undefined>|undefined) | ||
* }} | ||
*/ | ||
var Options; | ||
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/** | ||
* Describes a command's termination conditions. | ||
* @param {?number} code The exit code, or {@code null} if the command did not | ||
* exit normally. | ||
* @param {?string} signal The signal used to kill the command, or | ||
* {@code null}. | ||
* @constructor | ||
*/ | ||
var Result = function(code, signal) { | ||
/** @type {?number} */ | ||
this.code = code; | ||
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/** @type {?string} */ | ||
this.signal = signal; | ||
}; | ||
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/** | ||
* Represents a command running in a sub-process. | ||
* @param {!promise.Promise.<!Result>} result The command result. | ||
* @constructor | ||
*/ | ||
var Command = function(result, onKill) { | ||
/** @return {boolean} Whether this command is still running. */ | ||
this.isRunning = function() { | ||
return result.isPending(); | ||
}; | ||
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/** | ||
* @return {!promise.Promise.<!Result>} A promise for the result of this | ||
* command. | ||
*/ | ||
this.result = function() { | ||
return result; | ||
}; | ||
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/** | ||
* Sends a signal to the underlying process. | ||
* @param {string=} opt_signal The signal to send; defaults to | ||
* {@code SIGTERM}. | ||
*/ | ||
this.kill = function(opt_signal) { | ||
onKill(opt_signal || 'SIGTERM'); | ||
}; | ||
}; | ||
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// PUBLIC API | ||
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/** | ||
* Spawns a child process. The returned {@link Command} may be used to wait | ||
* for the process result or to send signals to the process. | ||
* | ||
* @param {string} command The executable to spawn. | ||
* @param {Options=} opt_options The command options. | ||
* @return {!Command} The launched command. | ||
*/ | ||
module.exports = function(command, opt_options) { | ||
var options = opt_options || {}; | ||
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var proc = childProcess.spawn(command, options.args || [], { | ||
env: options.env || process.env, | ||
stdio: options.stdio || 'ignore' | ||
}).once('exit', onExit); | ||
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// This process should not wait on the spawned child, however, we do | ||
// want to ensure the child is killed when this process exits. | ||
proc.unref(); | ||
process.once('exit', killCommand); | ||
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var result = promise.defer(); | ||
var cmd = new Command(result.promise, function(signal) { | ||
if (!result.isPending() || !proc) { | ||
return; // No longer running. | ||
} | ||
proc.kill(signal); | ||
}); | ||
return cmd; | ||
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function onExit(code, signal) { | ||
proc = null; | ||
process.removeListener('exit', killCommand); | ||
result.fulfill(new Result(code, signal)); | ||
} | ||
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function killCommand() { | ||
process.removeListener('exit', killCommand); | ||
proc && proc.kill('SIGTERM'); | ||
} | ||
}; |
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