feat(hide, expose): allow the user to hide/expose globals for the compiled expressions and codes

Author: solkimicreb

README.md

@@ -76,6 +76,32 @@ context.item = {name: 'item name'}
 result = expression(context) // result is 'item name'
 ```
 
+### compiler.expose(String)
+
+Use this method to expose globals to the compiler. Non of the globals are exposed by default.
+
+```js
+const code = compiler.compileCode('console.log(message)')
+compiler.expose('console')
+code({message: 'Hello World'}) // logs 'Hello World' to the console
+```
+
+Context variables are always favored over global ones, when both are present (with the same name).
+
+### compiler.hide(String)
+
+Use this method to hide exposed globals from the compiler.
+
+```js
+const code = compiler.compileCode('console.log(message)')
+compiler.expose('console')
+code({message: 'Hello World'}) // logs 'Hello World' to the console
+compiler.hide('console')
+code({message: 'Hello World'}) // throws an error, console is undefined
+```
+
+Context variables are always favored over global ones, when both are present (with the same name).
+
 ## Example
 
 ```js

compiler.js

@@ -2,7 +2,9 @@
 
 module.exports = {
   compileCode,
-  compileExpression
+  compileExpression,
+  expose,
+  hide
 }
 
 let globalObj
@@ -15,6 +17,7 @@ globalObj.$nxCompileCreateBackup = createBackup
 const proxies = new WeakMap()
 const expressionCache = new Map()
 const codeCache = new Map()
+const exposedGlobals = new Set()
 const handlers = {has}
 
 function compileExpression (src) {
@@ -39,7 +42,7 @@ function compileCode (src) {
   }
   let code = codeCache.get(src)
   if (!code) {
-    code = new Function('context, tempVars', // eslint-disable-line
+    code = new Function('context', 'tempVars', // eslint-disable-line
     `const backup = $nxCompileCreateBackup(context, tempVars)
     Object.assign(context, tempVars)
     const sandbox = $nxCompileToSandbox(context)
@@ -53,6 +56,20 @@ function compileCode (src) {
   return code
 }
 
+function expose (globalName) {
+  if (typeof globalName !== 'string') {
+    throw new TypeError('first argument must be a string')
+  }
+  exposedGlobals.add(globalName)
+}
+
+function hide (globalName) {
+  if (typeof globalName !== 'string') {
+    throw new TypeError('first argument must be a string')
+  }
+  exposedGlobals.delete(globalName)
+}
+
 function toSandbox (obj) {
   if (typeof obj !== 'object') {
     throw new TypeError('first argument must be an object')
@@ -75,6 +92,6 @@ function createBackup (context, tempVars) {
   }
 }
 
-function has () {
-  return true
+function has (target, key) {
+  return exposedGlobals.has(key) ? Reflect.has(target, key) : true
 }

compiler.test.js

@@ -79,4 +79,39 @@ describe('nx-compile', () => {
       expect(context.tempVar).to.be.undefined
     })
   })
+
+  describe('expose', () => {
+    it('should throw a TypeError on non string source argument', () => {
+      expect(() => compiler.expose({})).to.throw(TypeError)
+      expect(() => compiler.expose(undefined)).to.throw(TypeError)
+      expect(() => compiler.expose(12)).to.throw(TypeError)
+    })
+
+    it('should expose the passed global', () => {
+      const expression = compiler.compileExpression('console')
+      expect(expression({})).to.be.undefined
+      compiler.expose('console')
+      expect(expression({})).to.equal(console)
+    })
+
+    it('should favour sandbox props over exposed globals', () => {
+      const expression = compiler.compileExpression('console')
+      expect(expression({ console: 'prop' })).to.equal('prop')
+    })
+  })
+
+  describe('hide', () => {
+    it('should throw a TypeError on non string source argument', () => {
+      expect(() => compiler.hide({})).to.throw(TypeError)
+      expect(() => compiler.hide(undefined)).to.throw(TypeError)
+      expect(() => compiler.hide(12)).to.throw(TypeError)
+    })
+
+    it('should hide exposed globals', () => {
+      const expression = compiler.compileExpression('console')
+      expect(expression({})).to.equal(console)
+      compiler.hide('console')
+      expect(expression({})).to.be.undefined
+    })
+  })
 })