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var path = require('path'),
fs = require('fs'),
f = require('util').format,
resolveFrom = require('resolve-from'),
semver = require('semver');
var exists = fs.existsSync || path.existsSync;
var find_package_json = function(location) {
var found = false;
while(!found) {
if (exists(location + '/package.json')) {
found = location;
} else if (location !== '/') {
location = path.dirname(location);
} else {
return false;
}
}
return location;
}
var require_optional = function(name, options) {
options = options || {};
options.strict = typeof options.strict == 'boolean' ? options.strict : true;
// Current location
var location = __dirname;
// Check if we have a parent
if(module.parent) {
location = module.parent.filename;
}
// Locate this module's package.json file
var location = find_package_json(location);
if(!location) {
throw new Error('package.json can not be located');
}
// Read the package.json file
var object = JSON.parse(fs.readFileSync(f('%s/package.json', location)));
// Is the name defined by interal file references
var parts = name.split(/\//);
// Optional dependencies exist
if(!object.peerOptionalDependencies) {
throw new Error(f('no optional dependency [%s] defined in peerOptionalDependencies in package.json', parts[0]));
} else if(object.peerOptionalDependencies && !object.peerOptionalDependencies[parts[0]]) {
throw new Error(f('no optional dependency [%s] defined in peerOptionalDependencies in package.json', parts[0]));
}
// Unpack the expected version
var expectedVersions = object.peerOptionalDependencies[parts[0]];
// The resolved package
var moduleEntry = undefined;
// Module file
var moduleEntryFile = name;
try {
// Validate if it's possible to read the module
moduleEntry = require(moduleEntryFile);
} catch(err) {
// Attempt to resolve in top level package
try {
// Get the module entry file
moduleEntryFile = resolveFrom(process.cwd(), name);
if(moduleEntryFile == null) return undefined;
// Attempt to resolve the module
moduleEntry = require(moduleEntryFile);
} catch(err) {
if(err.code === 'MODULE_NOT_FOUND') return undefined;
}
}
// Resolve the location of the module's package.json file
var location = find_package_json(require.resolve(moduleEntryFile));
if(!location) {
throw new Error('package.json can not be located');
}
// Read the module file
var dependentOnModule = JSON.parse(fs.readFileSync(f('%s/package.json', location)));
// Get the version
var version = dependentOnModule.version;
// Validate if the found module satisfies the version id
if(semver.satisfies(version, expectedVersions) == false
&& options.strict) {
var error = new Error(f('optional dependency [%s] found but version [%s] did not satisfy constraint [%s]', parts[0], version, expectedVersions));
error.code = 'OPTIONAL_MODULE_NOT_FOUND';
throw error;
}
// Satifies the module requirement
return moduleEntry;
}
require_optional.exists = function(name) {
try {
var m = require_optional(name);
if(m === undefined) return false;
return true;
} catch(err) {
return false;
}
}
module.exports = require_optional;
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