Initial release

.gitignore

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+node_modules/
+.idea/

README.md

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-# shrinkwrap-to-lockfile
-Migrate npm shrinkwrap to yarn lockfile
+# NPM Shrinkwrap to Yarn lockfile
+
+Migrate your `npm-shrinkwrap.json` to a yarn lockfile without a headache!
+
+There is three steps we perform with this migration:
+* We extract the dependencies from the `npm-shrinkwrap.json`;
+* We save and lock down these dependencies in the `package.json` (removing the ~ or ^); 
+* We generate a new `yarn.lock` file from the updated `package.json`.
+
+## Installation
+
+```bash
+yarn global add shrinkwrap-to-lockfile
+```
+
+## How to use
+
+```bash
+shrinkwrap-to-lockfile [npm-shrinkwrap-file] [package-file]
+```
+
+That's it!

bin/cli.js

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+#!/usr/bin/env node
+
+require('..')(...process.argv.slice(2));

index.js

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+const fs = require('fs');
+const path = require('path');
+const exec = require('child_process').exec;
+
+const _ = require('lodash');
+
+function parseJsonFile(filename) {
+  let obj = {};
+
+  try {
+    const file = fs.readFileSync(path.resolve(process.cwd(), filename), 'utf8');
+    obj = JSON.parse(file);
+  } catch (error) {
+    throw new Error(`${filename} could not be parsed.`);
+  }
+
+  return obj;
+}
+
+function getDependencyVersions(dependencies) {
+  return _.reduce(dependencies, (result, pkg, name) => {
+    const version = pkg.version || pkg;
+    result[name] = _.head(version.match(/(\d+\.\d+\.\d+(?:-.+)?)/));
+
+    return result;
+  }, {});
+}
+
+function objectMergeLeft(a, b) {
+  return _.reduce(a, (result, value, key) => {
+    result[key] = value;
+
+    if (!_.isEqual(value, b[key])) {
+      result[key] = b[key];
+    }
+
+    return result;
+  }, {});
+}
+
+function updatePackageJson(shrinkwrapFile, packageFile) {
+  const shrinkwrapJson = parseJsonFile(shrinkwrapFile);
+  const packageJson = parseJsonFile(packageFile);
+
+  const shrinkwrapVersions = getDependencyVersions(shrinkwrapJson.dependencies);
+
+  if (packageJson.dependencies) {
+    const dependencyVersions = getDependencyVersions(packageJson.dependencies);
+    packageJson.dependencies = objectMergeLeft(dependencyVersions, shrinkwrapVersions);
+  }
+
+  if (packageJson.devDependencies) {
+    const devDependencyVersions = getDependencyVersions(packageJson.devDependencies);
+    packageJson.devDependencies = objectMergeLeft(devDependencyVersions, shrinkwrapVersions);
+  }
+
+  fs.writeFileSync(path.resolve(__dirname, 'package.json'), JSON.stringify(packageJson, null, 2));
+}
+
+function createLockFile() {
+  exec('yarn install');
+}
+
+function shrinkwrapToLockfile(shrinkwrap = 'npm-shrinkwrap.json', packageJson = 'package.json') {
+  updatePackageJson(shrinkwrap, packageJson);
+  createLockFile();
+}
+
+module.exports = shrinkwrapToLockfile;

package.json

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+{
+  "name": "shrinkwrap-to-lockfile",
+  "version": "1.0.0",
+  "description": "Migrate your npm shrinkwrap to a yarn lockfile.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "bin": {
+    "shrinkwrap-to-lockfile": "bin/cli.js"
+  },
+  "author": "Matthijs Dabroek <dabroek@gmail.com>",
+  "license": "MIT",
+  "dependencies": {
+    "lodash": "^4.17.4"
+  }
+}

yarn.lock

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+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+lodash@4.17.4:
+  version "4.17.4"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.4.tgz#78203a4d1c328ae1d86dca6460e369b57f4055ae"