Improve pipeline-operator typings (#14629)

* refactor: simplify buildOptimizedSequenceExpression

* proposal-pipeline-operator

* address review comments

packages/babel-plugin-proposal-pipeline-operator/src/buildOptimizedSequenceExpression.ts

@@ -1,58 +1,73 @@
 import { types as t } from "@babel/core";
+import type { NodePath } from "@babel/traverse";
 
 // tries to optimize sequence expressions in the format
 //   (a = b, (c => c + e)(a))
 // to
 //   (a = b, a + e)
-const buildOptimizedSequenceExpression = ({ call, path, placeholder }) => {
+
+type Options = {
+  call: t.CallExpression | t.AwaitExpression;
+  path: NodePath<t.BinaryExpression & { operator: "|>" }>;
+  placeholder: t.Identifier;
+};
+
+function isConciseArrowExpression(
+  node: t.Node,
+): node is t.ArrowFunctionExpression & { body: t.Expression } {
+  return (
+    t.isArrowFunctionExpression(node) &&
+    t.isExpression(node.body) &&
+    !node.async
+  );
+}
+
+const buildOptimizedSequenceExpression = ({
+  call,
+  path,
+  placeholder,
+}: Options) => {
+  // @ts-expect-error AwaitExpression does not have callee property
   const { callee: calledExpression } = call;
-  const pipelineLeft = path.node.left;
+  // pipelineLeft must not be a PrivateName
+  const pipelineLeft = path.node.left as t.Expression;
   const assign = t.assignmentExpression(
     "=",
     t.cloneNode(placeholder),
     pipelineLeft,
   );
 
-  let optimizeArrow =
-    t.isArrowFunctionExpression(calledExpression) &&
-    t.isExpression(calledExpression.body) &&
-    !calledExpression.async &&
-    !calledExpression.generator;
-  let param;
+  const expressionIsArrow = isConciseArrowExpression(calledExpression);
 
-  if (optimizeArrow) {
+  if (expressionIsArrow) {
+    let param;
+    let optimizeArrow = true;
     const { params } = calledExpression;
     if (params.length === 1 && t.isIdentifier(params[0])) {
       param = params[0];
     } else if (params.length > 0) {
       optimizeArrow = false;
     }
+    if (optimizeArrow && !param) {
+      // fixme: arrow function with 1 pattern argument will also go into this branch
+      // Arrow function with 0 arguments
+      return t.sequenceExpression([pipelineLeft, calledExpression.body]);
+    } else if (param) {
+      path.scope.push({ id: t.cloneNode(placeholder) });
+      path.get("right").scope.rename(param.name, placeholder.name);
+
+      return t.sequenceExpression([assign, calledExpression.body]);
+    }
   } else if (t.isIdentifier(calledExpression, { name: "eval" })) {
     const evalSequence = t.sequenceExpression([
       t.numericLiteral(0),
       calledExpression,
     ]);
 
-    call.callee = evalSequence;
-
-    path.scope.push({ id: t.cloneNode(placeholder) });
-
-    return t.sequenceExpression([assign, call]);
-  }
-
-  if (optimizeArrow && !param) {
-    // Arrow function with 0 arguments
-    return t.sequenceExpression([pipelineLeft, calledExpression.body]);
+    (call as t.CallExpression).callee = evalSequence;
   }
-
   path.scope.push({ id: t.cloneNode(placeholder) });
 
-  if (param) {
-    path.get("right").scope.rename(param.name, placeholder.name);
-
-    return t.sequenceExpression([assign, calledExpression.body]);
-  }
-
   return t.sequenceExpression([assign, call]);
 };
 

packages/babel-plugin-proposal-pipeline-operator/src/fsharpVisitor.ts

@@ -1,7 +1,8 @@
-import { types as t } from "@babel/core";
+import { types as t, type PluginObject } from "@babel/core";
+import type { NodePath } from "@babel/traverse";
 import buildOptimizedSequenceExpression from "./buildOptimizedSequenceExpression";
 
-const fsharpVisitor = {
+const fsharpVisitor: PluginObject["visitor"] = {
   BinaryExpression(path) {
     const { scope, node } = path;
     const { operator, left, right } = node;
@@ -16,7 +17,7 @@ const fsharpVisitor = {
     const sequence = buildOptimizedSequenceExpression({
       placeholder,
       call,
-      path,
+      path: path as NodePath<t.BinaryExpression & { operator: "|>" }>,
     });
     path.replaceWith(sequence);
   },

packages/babel-plugin-proposal-pipeline-operator/src/hackVisitor.ts

@@ -33,7 +33,7 @@ const topicReferenceVisitor: Visitor<State> = {
 // with sequence expressions containing assignment expressions
 // with automatically generated variables,
 // from inside to outside, from left to right.
-export default {
+const visitor: Visitor<PluginPass> = {
   BinaryExpression: {
     exit(path) {
       const { scope, node } = path;
@@ -52,7 +52,7 @@ export default {
         return;
       }
 
-      const visitorState = {
+      const visitorState: State = {
         topicReferences: [],
         // pipeBodyPath might be a function, and it won't be visited by
         // topicReferenceVisitor because traverse() skips the top-level
@@ -93,4 +93,6 @@ export default {
       );
     },
   },
-} as Visitor<PluginPass>;
+};
+
+export default visitor;

packages/babel-plugin-proposal-pipeline-operator/src/minimalVisitor.ts

@@ -1,7 +1,8 @@
-import { types as t } from "@babel/core";
+import { types as t, type PluginPass } from "@babel/core";
+import type { NodePath, Visitor } from "@babel/traverse";
 import buildOptimizedSequenceExpression from "./buildOptimizedSequenceExpression";
 
-const minimalVisitor = {
+const minimalVisitor: Visitor<PluginPass> = {
   BinaryExpression(path) {
     const { scope, node } = path;
     const { operator, left, right } = node;
@@ -14,7 +15,7 @@ const minimalVisitor = {
       buildOptimizedSequenceExpression({
         placeholder,
         call,
-        path,
+        path: path as NodePath<t.BinaryExpression & { operator: "|>" }>,
       }),
     );
   },