set up initial transformer framework

Author: David Sheldrick

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Typescript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+
+dist

.vscode/settings.json

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+// Place your settings in this file to overwrite default and user settings.
+{
+  "search.exclude": {
+    "**/node_modules": true,
+    "**/bower_components": true,
+    "dist": true
+  },
+  "editor.formatOnPaste": true,
+  "prettier.semi": false,
+  "prettier.trailingComma": "all",
+  "editor.formatOnSave": true
+}

LICENSE

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+Copyright (c) 2018 David Sheldrick
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

package.json

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+{
+  "name": "react-native-obfuscating-transformer",
+  "version": "1.0.0-0",
+  "description": "Obfuscating transformer for react-native",
+  "main": "dist/index.js",
+  "repository": "https://github.com/ds300/react-native-obfuscating-transformer",
+  "author": "David Sheldrick",
+  "license": "MIT",
+  "dependencies": {
+    "@types/babel-core": "^6.25.3",
+    "@types/node": "^9.3.0",
+    "@types/semver": "^5.4.0",
+    "app-root-path": "^2.0.1",
+    "jju": "^1.3.0",
+    "semver": "^5.4.1",
+    "source-map": "^0.6.1"
+  },
+  "peerDependencies": {
+    "react-native": ">=0.45.0"
+  },
+  "scripts": {
+    "precommit": "tsc && lint-staged",
+    "test": "jest"
+  },
+  "lint-staged": {
+    "*.ts": ["prettier --no-semi --single-quote --trailing-comma es5"]
+  },
+  "devDependencies": {
+    "babel-preset-react-native": "^1.9.1",
+    "husky": "^0.13.3",
+    "jest": "^22.0.6",
+    "lint-staged": "^3.4.1",
+    "metro": "^0.24.3",
+    "metro-bundler": "^0.9.0",
+    "np": "^2.15.0",
+    "prettier": "^1.10.2",
+    "react-native": "^0.45.1",
+    "ts-jest": "^22.0.1",
+    "typescript": "^2.6.2"
+  },
+  "jest": {
+    "transform": {
+      ".(ts|tsx)": "<rootDir>/node_modules/ts-jest/preprocessor.js"
+    },
+    "testRegex": "src/.*(/__tests__/.*|\\.(test|spec))\\.(ts|tsx|js)$",
+    "moduleFileExtensions": ["ts", "tsx", "js"]
+  }
+}

src/getCallerFile.ts

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+// This code taken from https://stackoverflow.com/a/29581862/1382997
+// Question by einstein https://stackoverflow.com/users/449132/einstein
+// Answer by Rhionin https://stackoverflow.com/users/1751376/rhionin
+export function getCallerFile() {
+  const originalFunc = Error.prepareStackTrace
+
+  let callerfile
+
+  try {
+    const err = new Error() as any
+    var currentfile
+
+    Error.prepareStackTrace = function(_, stack) {
+      return stack
+    }
+
+    currentfile = err.stack.shift().getFileName()
+
+    // go up two places in the stack trace. i.e. out of this file, and out of index.ts
+    for (let i = 0; i < 2; i++) {
+      while (err.stack.length) {
+        callerfile = err.stack.shift().getFileName()
+
+        if (currentfile !== callerfile) break
+      }
+
+      currentfile = callerfile
+    }
+  } catch (e) {}
+
+  Error.prepareStackTrace = originalFunc
+
+  return callerfile
+}

src/getMetroTransformer.ts

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+import { Node } from "babel-core"
+import { RawSourceMap } from "source-map"
+import * as semver from "semver"
+
+export interface MetroTransformer {
+  transform(props: {
+    filename: string
+    src: string
+    options: object
+  }): { ast?: Node; code?: string; map?: string | RawSourceMap }
+  getCacheKey?(): string
+}
+
+export function getMetroTransformer(): MetroTransformer {
+  const reactNativeVersionString = require("react-native/package.json").version
+
+  const parseResult = semver.parse(reactNativeVersionString)
+
+  if (!parseResult) {
+    throw new Error(
+      `Can't parse react-native version string '${reactNativeVersionString}'`,
+    )
+  }
+
+  const reactNativeMinorVersion = parseResult.minor
+
+  if (reactNativeMinorVersion >= 52) {
+    return require("metro/src/transformer")
+  } else if (reactNativeMinorVersion >= 0.47) {
+    return require("metro-bundler/src/transformer")
+  } else if (reactNativeMinorVersion === 0.46) {
+    return require("metro-bundler/build/transformer")
+  } else {
+    throw new Error(
+      `react-native-obfuscating-transformer requires react-native >= 0.46, you are on version ${reactNativeVersionString}`,
+    )
+  }
+}

src/index.ts

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+import * as crypto from "crypto"
+import * as fs from "fs"
+
+import { getCallerFile } from "./getCallerFile"
+import { MetroTransformer, getMetroTransformer } from "./getMetroTransformer"
+
+function getOwnCacheKey(upstreamCacheKey: string, callerFilename: string) {
+  var key = crypto.createHash("md5")
+  key.update(upstreamCacheKey)
+  key.update(fs.readFileSync(__filename))
+  key.update(fs.readFileSync(callerFilename))
+  return key.digest("hex")
+}
+
+interface ObfuscationOptions {
+  match?: RegExp
+  upstreamTransformer?: MetroTransformer
+}
+
+function obfuscatingTransformer({
+  match = /.*.js/,
+  upstreamTransformer = getMetroTransformer(),
+  ..._options
+}: ObfuscationOptions): MetroTransformer {
+  const callerFilename = getCallerFile()
+
+  return {
+    transform(props) {
+      const result = upstreamTransformer.transform(props)
+      if (props.filename.match(match)) {
+        console.log("obfuscating", props.filename)
+      }
+      return result
+    },
+    getCacheKey() {
+      return getOwnCacheKey(
+        upstreamTransformer.getCacheKey
+          ? upstreamTransformer.getCacheKey()
+          : "",
+        callerFilename,
+      )
+    },
+  }
+}
+
+export = obfuscatingTransformer

tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "es5",
+    "module": "commonjs",
+    "lib": [
+      "es2015"
+    ],
+    "strict": true,
+    "outDir": "dist",
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "inlineSourceMap": true,
+    "allowJs": true,
+    "inlineSources": true
+  },
+  "include": [
+    "typings/**/*.d.ts",
+    "src/**/*.ts"
+  ],
+  "compileOnSave": true
+}