WIP - add extractor, generate snippet_data

node_modules/babel-plugin-transform-remove-undefined/lib/index.js

@@ -0,0 +1,240 @@
+"use strict";
+
+var evaluate = require("babel-helper-evaluate-path");
+
+function isPureAndUndefined(rval) {
+  var _ref = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {},
+      tdz = _ref.tdz,
+      _ref$scope = _ref.scope,
+      scope = _ref$scope === undefined ? { hasBinding: function hasBinding() {
+      return false;
+    } } : _ref$scope;
+
+  if (rval.isIdentifier() && rval.node.name === "undefined") {
+    // deopt right away if undefined is a local binding
+    if (scope.hasBinding(rval.node.name, true /* no globals */)) {
+      return false;
+    }
+    return true;
+  }
+
+  if (!rval.isPure()) {
+    return false;
+  }
+  var evaluation = evaluate(rval, { tdz });
+  return evaluation.confident === true && evaluation.value === undefined;
+}
+
+function getLoopParent(path, scopeParent) {
+  var parent = path.findParent(function (p) {
+    return p.isLoop() || p === scopeParent;
+  });
+  // don't traverse higher than the function the var is defined in.
+  return parent === scopeParent ? null : parent;
+}
+
+function getFunctionParent(path, scopeParent) {
+  var parent = path.findParent(function (p) {
+    return p.isFunction();
+  });
+  // don't traverse higher than the function the var is defined in.
+  return parent === scopeParent ? null : parent;
+}
+
+function getFunctionReferences(path, scopeParent) {
+  var references = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : new Set();
+
+  for (var func = getFunctionParent(path, scopeParent); func; func = getFunctionParent(func, scopeParent)) {
+    var id = func.node.id;
+    var binding = id && func.scope.getBinding(id.name);
+
+    if (!binding) {
+      continue;
+    }
+
+    binding.referencePaths.forEach(function (path) {
+      if (!references.has(path)) {
+        references.add(path);
+        getFunctionReferences(path, scopeParent, references);
+      }
+    });
+  }
+  return references;
+}
+
+function hasViolation(declarator, scope, start) {
+  var binding = scope.getBinding(declarator.node.id.name);
+  if (!binding) {
+    return true;
+  }
+
+  var scopeParent = declarator.getFunctionParent();
+
+  var violation = binding.constantViolations.some(function (v) {
+    // https://github.com/babel/minify/issues/630
+    if (!v.node) {
+      return false;
+    }
+    // return 'true' if we cannot guarantee the violation references
+    // the initialized identifier after
+    var violationStart = v.node.start;
+    if (violationStart === undefined || violationStart < start) {
+      return true;
+    }
+
+    var references = getFunctionReferences(v, scopeParent);
+    var _iteratorNormalCompletion = true;
+    var _didIteratorError = false;
+    var _iteratorError = undefined;
+
+    try {
+      for (var _iterator = references[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+        var ref = _step.value;
+
+        if (ref.node.start === undefined || ref.node.start < start) {
+          return true;
+        }
+      }
+    } catch (err) {
+      _didIteratorError = true;
+      _iteratorError = err;
+    } finally {
+      try {
+        if (!_iteratorNormalCompletion && _iterator.return) {
+          _iterator.return();
+        }
+      } finally {
+        if (_didIteratorError) {
+          throw _iteratorError;
+        }
+      }
+    }
+
+    for (var loop = getLoopParent(declarator, scopeParent); loop; loop = getLoopParent(loop, scopeParent)) {
+      if (loop.node.end === undefined || loop.node.end > violationStart) {
+        return true;
+      }
+    }
+  });
+
+  return violation;
+}
+
+module.exports = function () {
+  return {
+    name: "transform-remove-undefined",
+    visitor: {
+      SequenceExpression(path, _ref2) {
+        var _ref2$opts = _ref2.opts;
+        _ref2$opts = _ref2$opts === undefined ? {} : _ref2$opts;
+        var tdz = _ref2$opts.tdz;
+
+        var expressions = path.get("expressions");
+
+        for (var i = 0; i < expressions.length; i++) {
+          var expr = expressions[i];
+          if (!isPureAndUndefined(expr, { tdz, scope: path.scope })) continue;
+
+          // last value
+          if (i === expressions.length - 1) {
+            if (path.parentPath.isExpressionStatement()) {
+              expr.remove();
+            }
+          } else {
+            expr.remove();
+          }
+        }
+      },
+
+      ReturnStatement(path, _ref3) {
+        var _ref3$opts = _ref3.opts;
+        _ref3$opts = _ref3$opts === undefined ? {} : _ref3$opts;
+        var tdz = _ref3$opts.tdz;
+
+        if (path.node.argument !== null) {
+          if (isPureAndUndefined(path.get("argument"), {
+            tdz,
+            scope: path.scope
+          })) {
+            path.node.argument = null;
+          }
+        }
+      },
+
+      VariableDeclaration(path, _ref4) {
+        var _ref4$opts = _ref4.opts;
+        _ref4$opts = _ref4$opts === undefined ? {} : _ref4$opts;
+        var tdz = _ref4$opts.tdz;
+
+        switch (path.node.kind) {
+          case "const":
+            break;
+          case "let":
+            var _iteratorNormalCompletion2 = true;
+            var _didIteratorError2 = false;
+            var _iteratorError2 = undefined;
+
+            try {
+              for (var _iterator2 = path.get("declarations")[Symbol.iterator](), _step2; !(_iteratorNormalCompletion2 = (_step2 = _iterator2.next()).done); _iteratorNormalCompletion2 = true) {
+                var declarator = _step2.value;
+
+                if (isPureAndUndefined(declarator.get("init"), { tdz })) {
+                  declarator.node.init = null;
+                }
+              }
+            } catch (err) {
+              _didIteratorError2 = true;
+              _iteratorError2 = err;
+            } finally {
+              try {
+                if (!_iteratorNormalCompletion2 && _iterator2.return) {
+                  _iterator2.return();
+                }
+              } finally {
+                if (_didIteratorError2) {
+                  throw _iteratorError2;
+                }
+              }
+            }
+
+            break;
+          case "var":
+            var start = path.node.start;
+            if (start === undefined) {
+              // This is common for plugin-generated nodes
+              break;
+            }
+            var scope = path.scope;
+            var _iteratorNormalCompletion3 = true;
+            var _didIteratorError3 = false;
+            var _iteratorError3 = undefined;
+
+            try {
+              for (var _iterator3 = path.get("declarations")[Symbol.iterator](), _step3; !(_iteratorNormalCompletion3 = (_step3 = _iterator3.next()).done); _iteratorNormalCompletion3 = true) {
+                var _declarator = _step3.value;
+
+                if (isPureAndUndefined(_declarator.get("init")) && !hasViolation(_declarator, scope, start)) {
+                  _declarator.node.init = null;
+                }
+              }
+            } catch (err) {
+              _didIteratorError3 = true;
+              _iteratorError3 = err;
+            } finally {
+              try {
+                if (!_iteratorNormalCompletion3 && _iterator3.return) {
+                  _iterator3.return();
+                }
+              } finally {
+                if (_didIteratorError3) {
+                  throw _iteratorError3;
+                }
+              }
+            }
+
+            break;
+        }
+      }
+    }
+  };
+};