Partial application plugin

packages/babel-parser/test/fixtures/experimental/partial-application/call-expr/output.json

@@ -96,4 +96,4 @@
     ],
     "directives": []
   }
-}
+}

packages/babel-parser/test/fixtures/experimental/partial-application/call-on-SuperProperty/output.json

@@ -302,4 +302,4 @@
     ],
     "directives": []
   }
-}
+}

packages/babel-parser/test/fixtures/experimental/partial-application/for-any-arg/output.json

@@ -257,4 +257,4 @@
     ],
     "directives": []
   }
-}
+}

packages/babel-parser/test/fixtures/experimental/partial-application/from-left/output.json

@@ -227,4 +227,4 @@
     ],
     "directives": []
   }
-}
+}

packages/babel-parser/test/fixtures/experimental/partial-application/from-right/output.json

@@ -227,4 +227,4 @@
     ],
     "directives": []
   }
-}
+}

packages/babel-plugin-proposal-partial-application/.npmignore

@@ -0,0 +1,3 @@
+src
+test
+*.log

packages/babel-plugin-proposal-partial-application/README.md

@@ -0,0 +1,19 @@
+# @babel/plugin-proposal-partial-application
+
+>  Introduces a new ? token in an argument list which allows for partially applying an argument list to a call expression.
+
+See our website [@babel/plugin-proposal-partial-application](https://babeljs.io/docs/en/next/babel-plugin-proposal-partial-application.html) for more information.
+
+## Install
+
+Using npm:
+
+```sh
+npm install --save-dev @babel/plugin-proposal-partial-application
+```
+
+or using yarn:
+
+```sh
+yarn add @babel/plugin-proposal-partial-application --dev
+```

packages/babel-plugin-proposal-partial-application/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "@babel/plugin-proposal-partial-application",
+  "version": "7.2.0",
+  "description": "Introduces a new ? token in an argument list which allows for partially applying an argument list to a call expression",
+  "repository": "https://github.com/babel/babel/tree/master/packages/babel-plugin-proposal-partial-application",
+  "license": "MIT",
+  "publishConfig": {
+    "access": "public"
+  },
+  "main": "lib/index.js",
+  "keywords": [
+    "babel-plugin"
+  ],
+  "dependencies": {
+    "@babel/helper-plugin-utils": "^7.0.0",
+    "@babel/plugin-syntax-partial-application": "^7.2.0"
+  },
+  "peerDependencies": {
+    "@babel/core": "^7.0.0-0"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.2.0",
+    "@babel/helper-plugin-test-runner": "^7.0.0"
+  }
+}

packages/babel-plugin-proposal-partial-application/src/index.js

@@ -0,0 +1,151 @@
+import { declare } from "@babel/helper-plugin-utils";
+import syntaxPartialApplication from "@babel/plugin-syntax-partial-application";
+import { types as t } from "@babel/core";
+
+export default declare(api => {
+  api.assertVersion(7);
+
+  /**
+   * a function to figure out if a call expression has
+   * ArgumentPlaceholder as one of its arguments
+   * @param node a callExpression node
+   * @returns boolean
+   */
+  function hasArgumentPlaceholder(node) {
+    return node.arguments.some(arg => t.isArgumentPlaceholder(arg));
+  }
+
+  function unwrapArguments(node, scope) {
+    const init = [];
+    for (let i = 0; i < node.arguments.length; i++) {
+      if (
+        !t.isArgumentPlaceholder(node.arguments[i]) &&
+        !t.isImmutable(node.arguments[i])
+      ) {
+        const id = scope.generateUidIdentifierBasedOnNode(
+          node.arguments[i],
+          "param",
+        );
+        scope.push({ id });
+        if (t.isSpreadElement(node.arguments[i])) {
+          init.push(
+            t.assignmentExpression(
+              "=",
+              t.cloneNode(id),
+              t.arrayExpression([t.spreadElement(node.arguments[i].argument)]),
+            ),
+          );
+          node.arguments[i].argument = t.cloneNode(id);
+        } else {
+          init.push(
+            t.assignmentExpression("=", t.cloneNode(id), node.arguments[i]),
+          );
+          node.arguments[i] = t.cloneNode(id);
+        }
+      }
+    }
+    return init;
+  }
+
+  function replacePlaceholders(node, scope) {
+    const placeholders = [];
+    const args = [];
+
+    node.arguments.forEach(arg => {
+      if (t.isArgumentPlaceholder(arg)) {
+        const id = scope.generateUid("_argPlaceholder");
+        placeholders.push(t.identifier(id));
+        args.push(t.identifier(id));
+      } else {
+        args.push(arg);
+      }
+    });
+    return [placeholders, args];
+  }
+
+  return {
+    name: "proposal-partial-application",
+    inherits: syntaxPartialApplication,
+
+    visitor: {
+      CallExpression(path) {
+        if (!hasArgumentPlaceholder(path.node)) {
+          return;
+        }
+        const { node, scope } = path;
+        const functionLVal = path.scope.generateUidIdentifierBasedOnNode(
+          node.callee,
+        );
+
+        const argsInitializers = unwrapArguments(node, scope);
+        const [placeholdersParams, args] = replacePlaceholders(node, scope);
+
+        scope.push({ id: functionLVal });
+
+        if (node.callee.type === "MemberExpression") {
+          const receiverLVal = path.scope.generateUidIdentifierBasedOnNode(
+            node.callee.object,
+          );
+          scope.push({ id: receiverLVal });
+          const finalExpression = t.sequenceExpression([
+            t.assignmentExpression(
+              "=",
+              t.cloneNode(receiverLVal),
+              node.callee.object,
+            ),
+            t.assignmentExpression(
+              "=",
+              t.cloneNode(functionLVal),
+              t.memberExpression(
+                receiverLVal,
+                node.callee.property,
+                false,
+                false,
+              ),
+            ),
+            ...argsInitializers,
+            t.functionExpression(
+              node.callee.property,
+              placeholdersParams,
+              t.blockStatement(
+                [
+                  t.returnStatement(
+                    t.callExpression(
+                      t.memberExpression(
+                        functionLVal,
+                        t.identifier("call"),
+                        false,
+                        false,
+                      ),
+                      [receiverLVal, ...args],
+                    ),
+                  ),
+                ],
+                [],
+              ),
+              false,
+              false,
+            ),
+          ]);
+          path.replaceWith(finalExpression);
+        } else {
+          const finalExpression = t.sequenceExpression([
+            t.assignmentExpression("=", t.cloneNode(functionLVal), node.callee),
+            ...argsInitializers,
+            t.functionExpression(
+              node.callee,
+              placeholdersParams,
+              t.blockStatement(
+                [t.returnStatement(t.callExpression(functionLVal, args))],
+                [],
+              ),
+              false,
+              false,
+            ),
+          ]);
+          path.replaceWith(finalExpression);
+        }
+      },
+    },
+  };
+});

packages/babel-plugin-proposal-partial-application/test/fixtures/general/bound-method/exec.js

@@ -0,0 +1,16 @@
+class Partial {
+  constructor() {
+    this.compare = this.compare(?, ?);
+  }
+  compare(a, b) {
+    if(a > b){
+      return a;
+    }
+  }
+}
+
+const foo = new Partial;
+
+expect(foo.compare(3,1)).toEqual(3);
+expect(foo.compare.length).toEqual(2);
+expect(foo.compare.name).toEqual("compare");

packages/babel-plugin-proposal-partial-application/test/fixtures/general/bound-method/input.js

@@ -0,0 +1,10 @@
+class Collator {
+  constructor() {
+    this.compare = this.compare(?, ?);
+  }
+  compare(a, b) {
+    if (a > b) {
+      return a;
+    };
+  }
+}

packages/babel-plugin-proposal-partial-application/test/fixtures/general/bound-method/output.js

@@ -0,0 +1,18 @@
+class Collator {
+  constructor() {
+    var _this$compare, _this;
+
+    this.compare = (_this = this, _this$compare = _this.compare, function compare(_argPlaceholder, _argPlaceholder2) {
+      return _this$compare.call(_this, _argPlaceholder, _argPlaceholder2);
+    });
+  }
+
+  compare(a, b) {
+    if (a > b) {
+      return a;
+    }
+
+    ;
+  }
+
+}

packages/babel-plugin-proposal-partial-application/test/fixtures/general/from-left/exec.js

@@ -0,0 +1,8 @@
+"use strict";
+
+function add(x, y) { return x + y; }
+const addOne = add(1, ?);
+
+expect(addOne(2)).toEqual(3);
+expect(addOne.length).toEqual(1);
+expect(addOne.name).toEqual("add");

packages/babel-plugin-proposal-partial-application/test/fixtures/general/from-left/input.js

@@ -0,0 +1,3 @@
+"use strict";
+
+const foo = bar(?, 1);

packages/babel-plugin-proposal-partial-application/test/fixtures/general/from-left/output.js

@@ -0,0 +1,7 @@
+"use strict";
+
+var _bar;
+
+const foo = (_bar = bar, function bar(_argPlaceholder) {
+  return _bar(_argPlaceholder, 1);
+});

packages/babel-plugin-proposal-partial-application/test/fixtures/general/from-right/exec.js

@@ -0,0 +1,8 @@
+"use strict";
+
+function add(x, y) { return x + y; }
+const addTen = add(?, 10);
+
+expect(addTen(2)).toEqual(12);
+expect(addTen.length).toEqual(1);
+expect(addTen.name).toEqual("add");

packages/babel-plugin-proposal-partial-application/test/fixtures/general/from-right/input.js

@@ -0,0 +1,3 @@
+"use strict";
+
+const foo = bar(1, ?);

packages/babel-plugin-proposal-partial-application/test/fixtures/general/from-right/output.js

@@ -0,0 +1,7 @@
+"use strict";
+
+var _bar;
+
+const foo = (_bar = bar, function bar(_argPlaceholder) {
+  return _bar(1, _argPlaceholder);
+});

packages/babel-plugin-proposal-partial-application/test/fixtures/general/member-expression/exec.js

@@ -0,0 +1,7 @@
+"use strict";
+const obj = { add: (x, y) => x + y };
+const addOne = obj.add(1, ?);
+
+expect(addOne(5)).toEqual(6);
+expect(addOne.length).toEqual(1);
+expect(addOne.name).toEqual("add");

packages/babel-plugin-proposal-partial-application/test/fixtures/general/member-expression/input.js

@@ -0,0 +1,7 @@
+"use strict";
+
+const g = o.f(?, x, 1);
+
+const h = p.b(1, y, x, 2, ?);
+
+const j = a.b.c.d.e.foo(?, 1);

packages/babel-plugin-proposal-partial-application/test/fixtures/general/member-expression/output.js

@@ -0,0 +1,13 @@
+"use strict";
+
+var _x, _o$f, _o, _y, _x2, _p$b, _p, _a$b$c$d$e$foo, _a$b$c$d$e;
+
+const g = (_o = o, _o$f = _o.f, _x = x, function f(_argPlaceholder) {
+  return _o$f.call(_o, _argPlaceholder, _x, 1);
+});
+const h = (_p = p, _p$b = _p.b, _y = y, _x2 = x, function b(_argPlaceholder2) {
+  return _p$b.call(_p, 1, _y, _x2, 2, _argPlaceholder2);
+});
+const j = (_a$b$c$d$e = a.b.c.d.e, _a$b$c$d$e$foo = _a$b$c$d$e.foo, function foo(_argPlaceholder3) {
+  return _a$b$c$d$e$foo.call(_a$b$c$d$e, _argPlaceholder3, 1);
+});

packages/babel-plugin-proposal-partial-application/test/fixtures/general/multiple-calls/exec.js

@@ -0,0 +1,18 @@
+function add(a, b) {
+  return a + b;
+}
+
+function square(x){
+  return x * x;
+}
+
+const foo = add(?, 1);
+const bar = square(?);
+
+expect(bar(foo(2))).toEqual(9);
+expect(foo(2)).toEqual(3);
+expect(bar(4)).toEqual(16);
+expect(foo.length).toEqual(1);
+expect(foo.name).toEqual("add");
+expect(bar.length).toEqual(1);
+expect(bar.name).toEqual("square");

packages/babel-plugin-proposal-partial-application/test/fixtures/general/multiple-calls/input.js

@@ -0,0 +1,4 @@
+"use strict";
+
+const baz = ber(2, 4, ?, ?, 1);
+const foo = bar(1, ?, x, 3, ?);

packages/babel-plugin-proposal-partial-application/test/fixtures/general/multiple-calls/output.js

@@ -0,0 +1,10 @@
+"use strict";
+
+var _ber, _x, _bar;
+
+const baz = (_ber = ber, function ber(_argPlaceholder, _argPlaceholder2) {
+  return _ber(2, 4, _argPlaceholder, _argPlaceholder2, 1);
+});
+const foo = (_bar = bar, _x = x, function bar(_argPlaceholder3, _argPlaceholder4) {
+  return _bar(1, _argPlaceholder3, _x, 3, _argPlaceholder4);
+});

packages/babel-plugin-proposal-partial-application/test/fixtures/general/nested-calls/exec.js

@@ -0,0 +1,7 @@
+"use strict";
+
+function add(x, y) { return x + y; }
+const addOne = add(1, ?);
+const addTen = add(?, 10);
+
+expect(addOne(addTen(1))).toEqual(12);