babel-helper-evaluate-path - npm Package Compare versions

Comparing version 0.1.0 to 0.2.0

lib/index.js

 "use strict";
 
+var _slicedToArray = function () { function sliceIterator(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"]) _i["return"](); } finally { if (_d) throw _e; } } return _arr; } return function (arr, i) { if (Array.isArray(arr)) { return arr; } else if (Symbol.iterator in Object(arr)) { return sliceIterator(arr, i); } else { throw new TypeError("Invalid attempt to destructure non-iterable instance"); } }; }();
+
 module.exports = function evaluate(path) {
+  var _ref = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {},
+      _ref$tdz = _ref.tdz,
+      tdz = _ref$tdz === undefined ? false : _ref$tdz;
+
+  if (!tdz) {
+    return baseEvaluate(path);
+  }
+
+  if (path.isReferencedIdentifier()) {
+    return evaluateIdentifier(path);
+  }
+
+  var state = {
+    confident: true
+  };
+
+  // prepare
+  path.traverse({
+    Scope(scopePath) {
+      scopePath.skip();
+    },
+    ReferencedIdentifier(idPath) {
+      var binding = idPath.scope.getBinding(idPath.node.name);
+      // don't deopt globals
+      // let babel take care of it
+      if (!binding) return;
+
+      var evalResult = evaluateIdentifier(idPath);
+      if (!evalResult.confident) {
+        state.confident = evalResult.confident;
+        state.deoptPath = evalResult.deoptPath;
+      }
+    }
+  });
+
+  if (!state.confident) {
+    return state;
+  }
+
+  return baseEvaluate(path);
+};
+
+function baseEvaluate(path) {
   try {
@@ -12,2 +57,210 @@ return path.evaluate();
   }
-};
+}
+
+// Original Source:
+// https://github.com/babel/babel/blob/master/packages/babel-traverse/src/path/evaluation.js
+// modified for Babel-minify use
+function evaluateIdentifier(path) {
+  if (!path.isReferencedIdentifier()) {
+    throw new Error(`Expected ReferencedIdentifier. Got ${path.type}`);
+  }
+
+  var node = path.node;
+
+
+  var binding = path.scope.getBinding(node.name);
+
+  if (!binding) {
+    return deopt(path);
+  }
+
+  if (binding.constantViolations.length > 0) {
+    return deopt(binding.path);
+  }
+
+  // referenced in a different scope - deopt
+  if (shouldDeoptBasedOnScope(binding, path)) {
+    return deopt(path);
+  }
+
+  // let/var/const referenced before init
+  // or "var" referenced in an outer scope
+  var flowEvalResult = evaluateBasedOnControlFlow(binding, path);
+
+  if (flowEvalResult.confident) {
+    return flowEvalResult;
+  }
+
+  if (flowEvalResult.shouldDeopt) {
+    return deopt(path);
+  }
+
+  return path.evaluate();
+}
+
+// check if referenced in a different fn scope
+// we can't determine if this function is called sync or async
+// if the binding is in program scope
+// all it's references inside a different function should be deopted
+function shouldDeoptBasedOnScope(binding, refPath) {
+  if (binding.scope.path.isProgram() && refPath.scope !== binding.scope) {
+    return true;
+  }
+  return false;
+}
+
+function evaluateBasedOnControlFlow(binding, refPath) {
+  if (binding.kind === "var") {
+    // early-exit
+    var declaration = binding.path.parentPath;
+    if (declaration.parentPath.isIfStatement() || declaration.parentPath.isLoop() || declaration.parentPath.isSwitchCase()) {
+      return { shouldDeopt: true };
+    }
+
+    var blockParent = binding.path.scope.getBlockParent().path;
+    var fnParent = binding.path.getFunctionParent();
+
+    if (blockParent === fnParent) {
+      if (!fnParent.isProgram()) blockParent = blockParent.get("body");
+    }
+
+    // detect Usage Outside Init Scope
+    if (!blockParent.get("body").some(function (stmt) {
+      return stmt.isAncestor(refPath);
+    })) {
+      return { shouldDeopt: true };
+    }
+
+    // Detect usage before init
+    var stmts = fnParent.isProgram() ? fnParent.get("body") : fnParent.get("body").get("body");
+
+    var compareResult = compareBindingAndReference({
+      binding,
+      refPath,
+      stmts
+    });
+
+    if (compareResult.reference && compareResult.binding) {
+      if (compareResult.reference.scope === "current" && compareResult.reference.idx < compareResult.binding.idx) {
+        return { confident: true, value: void 0 };
+      }
+
+      return { shouldDeopt: true };
+    }
+  } else if (binding.kind === "let" || binding.kind === "const") {
+    // binding.path is the declarator
+    var declarator = binding.path;
+    var _declaration = declarator.parentPath;
+
+    if (_declaration.parentPath.isIfStatement() || _declaration.parentPath.isLoop() || _declaration.parentPath.isSwitchCase()) {
+      return { shouldDeopt: true };
+    }
+
+    var scopePath = declarator.scope.path;
+    if (scopePath.isFunction() || scopePath.isCatchClause()) {
+      scopePath = scopePath.get("body");
+    }
+
+    // Detect Usage before Init
+    var _stmts = scopePath.get("body");
+
+    var _compareResult = compareBindingAndReference({
+      binding,
+      refPath,
+      stmts: _stmts
+    });
+
+    if (_compareResult.reference && _compareResult.binding) {
+      if (_compareResult.reference.scope === "current" && _compareResult.reference.idx < _compareResult.binding.idx) {
+        throw new Error(`ReferenceError: Used ${refPath.node.name}: ` + `${binding.kind} binding before declaration`);
+      }
+      if (_compareResult.reference.scope === "other") {
+        return { shouldDeopt: true };
+      }
+    }
+  }
+
+  return { confident: false, shouldDeopt: false };
+}
+
+function compareBindingAndReference(_ref2) {
+  var binding = _ref2.binding,
+      refPath = _ref2.refPath,
+      stmts = _ref2.stmts;
+
+  var state = {
+    binding: null,
+    reference: null
+  };
+
+  var _iteratorNormalCompletion = true;
+  var _didIteratorError = false;
+  var _iteratorError = undefined;
+
+  try {
+    for (var _iterator = stmts.entries()[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+      var _ref3 = _step.value;
+
+      var _ref4 = _slicedToArray(_ref3, 2);
+
+      var idx = _ref4[0];
+      var stmt = _ref4[1];
+
+      if (stmt.isAncestor(binding.path)) {
+        state.binding = { idx };
+      }
+      var _iteratorNormalCompletion2 = true;
+      var _didIteratorError2 = false;
+      var _iteratorError2 = undefined;
+
+      try {
+        for (var _iterator2 = binding.referencePaths[Symbol.iterator](), _step2; !(_iteratorNormalCompletion2 = (_step2 = _iterator2.next()).done); _iteratorNormalCompletion2 = true) {
+          var ref = _step2.value;
+
+          if (ref === refPath && stmt.isAncestor(ref)) {
+            state.reference = {
+              idx,
+              scope: binding.path.scope === ref.scope ? "current" : "other"
+            };
+            break;
+          }
+        }
+      } catch (err) {
+        _didIteratorError2 = true;
+        _iteratorError2 = err;
+      } finally {
+        try {
+          if (!_iteratorNormalCompletion2 && _iterator2.return) {
+            _iterator2.return();
+          }
+        } finally {
+          if (_didIteratorError2) {
+            throw _iteratorError2;
+          }
+        }
+      }
+    }
+  } catch (err) {
+    _didIteratorError = true;
+    _iteratorError = err;
+  } finally {
+    try {
+      if (!_iteratorNormalCompletion && _iterator.return) {
+        _iterator.return();
+      }
+    } finally {
+      if (_didIteratorError) {
+        throw _iteratorError;
+      }
+    }
+  }
+
+  return state;
+}
+
+function deopt(deoptPath) {
+  return {
+    confident: false,
+    deoptPath
+  };
+}

package.json

 {
   "name": "babel-helper-evaluate-path",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "path.evaluate wrapped in a try catch",
-  "homepage": "https://github.com/babel/babili#readme",
-  "repository": "https://github.com/babel/babili/tree/master/packages/babel-helper-evaluate-path",
-  "bugs": "https://github.com/babel/babili/issues",
+  "keywords": [
+    "babel-minify",
+    "babel-plugin"
+  ],
+  "homepage": "https://github.com/babel/minify#readme",
+  "bugs": "https://github.com/babel/minify/issues",
+  "license": "MIT",
   "author": "boopathi",
-  "license": "MIT",
   "main": "lib/index.js",
-  "keywords": [
-    "babel-plugin",
-    "babili"
-  ],
-  "dependencies": {},
-  "devDependencies": {}
+  "repository": "https://github.com/babel/minify/tree/master/packages/babel-helper-evaluate-path"
 }

README.md

@@ -1,5 +0,31 @@
-# # babel-helper-evaluate-path
+# babel-helper-evaluate-path
 
-`path.evaluate` wrapped in a try catch
+A wrapper for babel's `path.evaluate`
 
+Fixes / Features:
+
++ Detect usages before initialization / declaration
+
+```js
+function foo() {
+  console.log(b); // ReferenceError
+  let b = 1;
+}
+
+function bar() {
+  console.log(a); // a is void 0
+  var a = 5;
+  console.log(a); // 5
+}
+```
+
++ Detect usages in scopes outside of initialization for vars (hoisted)
+
+```js
+function foo() {
+  if (a) var x = 5;
+  console.log(x); // cannot determine
+}
+```
+
 ## Installation
@@ -6,0 +32,0 @@

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Improved metrics

Total package byte prevSize

8592

increased by915.6%

Lines of code

219

increased by2090%

Number of lines in readme file

36

increased by260%

No dependency changes