Reduce transform-block-scoping loops output size (babel#15746)

Co-authored-by: Nicolò Ribaudo <[email protected]>
bigospolski · Jul 18, 2023 · b798a69 · b798a69
1 parent 11844c1
commit b798a69
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Showing 20 changed files with 451 additions and 182 deletions.
diff --git a/packages/babel-plugin-transform-block-scoping/src/loop.ts b/packages/babel-plugin-transform-block-scoping/src/loop.ts
@@ -254,45 +254,92 @@ export function wrapLoopBody(
     }
   }
   if (varNames.length) {
-    bodyStmts.push(
-      t.variableDeclaration(
-        "var",
-        varNames.map(name => t.variableDeclarator(t.identifier(name))),
-      ),
+    varPath.pushContainer(
+      "declarations",
+      varNames.map(name => t.variableDeclarator(t.identifier(name))),
     );
   }
 
-  if (state.breaksContinues.length === 0 && state.returns.length === 0) {
+  const labelNum = state.breaksContinues.length;
+  const returnNum = state.returns.length;
+  if (labelNum + returnNum === 0) {
     bodyStmts.push(t.expressionStatement(call));
+  } else if (labelNum === 1 && returnNum === 0) {
+    for (const path of state.breaksContinues) {
+      const { node } = path;
+      const { type, label } = node;
+      let name = type === "BreakStatement" ? "break" : "continue";
+      if (label) name += " " + label.name;
+      path.replaceWith(
+        t.addComment(
+          t.returnStatement(t.numericLiteral(1)),
+          "trailing",
+          " " + name,
+          true,
+        ),
+      );
+      if (updaterNode) path.insertBefore(t.cloneNode(updaterNode));
+
+      bodyStmts.push(
+        template.statement.ast`
+        if (${call}) ${node}
+      `,
+      );
+    }
   } else {
     const completionId = loopPath.scope.generateUid("ret");
-    bodyStmts.push(
-      t.variableDeclaration("var", [
-        t.variableDeclarator(t.identifier(completionId), call),
-      ]),
-    );
 
-    const injected = new Set<string>();
+    if (varPath.isVariableDeclaration()) {
+      varPath.pushContainer("declarations", [
+        t.variableDeclarator(t.identifier(completionId)),
+      ]);
+      bodyStmts.push(
+        t.expressionStatement(
+          t.assignmentExpression("=", t.identifier(completionId), call),
+        ),
+      );
+    } else {
+      bodyStmts.push(
+        t.variableDeclaration("var", [
+          t.variableDeclarator(t.identifier(completionId), call),
+        ]),
+      );
+    }
+
+    const injected: string[] = [];
     for (const path of state.breaksContinues) {
       const { node } = path;
       const { type, label } = node;
       let name = type === "BreakStatement" ? "break" : "continue";
-      if (label) name += "|" + label.name;
-      path.replaceWith(t.returnStatement(t.stringLiteral(name)));
+      if (label) name += " " + label.name;
+
+      let i = injected.indexOf(name);
+      const hasInjected = i !== -1;
+      if (!hasInjected) {
+        injected.push(name);
+        i = injected.length - 1;
+      }
+
+      path.replaceWith(
+        t.addComment(
+          t.returnStatement(t.numericLiteral(i)),
+          "trailing",
+          " " + name,
+          true,
+        ),
+      );
       if (updaterNode) path.insertBefore(t.cloneNode(updaterNode));
 
-      if (injected.has(name)) continue;
-      injected.add(name);
+      if (hasInjected) continue;
 
       bodyStmts.push(
         template.statement.ast`
-        if (
-          ${t.identifier(completionId)} === ${t.stringLiteral(name)}
-        ) ${node}
+        if (${t.identifier(completionId)} === ${t.numericLiteral(i)}) ${node}
       `,
       );
     }
-    if (state.returns.length) {
+
+    if (returnNum) {
       for (const path of state.returns) {
         const arg = path.node.argument || path.scope.buildUndefinedNode();
         path.replaceWith(
@@ -304,9 +351,10 @@ export function wrapLoopBody(
 
       bodyStmts.push(
         template.statement.ast`
-        if (typeof ${t.identifier(completionId)} === "object")
-          return ${t.identifier(completionId)}.v;
-      `,
+          if (${t.identifier(completionId)}) return ${t.identifier(
+            completionId,
+          )}.v;
+        `,
       );
     }
   }

diff --git a/...n-transform-block-scoping/test/fixtures/general/block-inside-switch-inside-loop/output.js b/...n-transform-block-scoping/test/fixtures/general/block-inside-switch-inside-loop/output.js
@@ -20,7 +20,7 @@ var j = 0;
 var _loop2 = function () {
   switch (i) {
     case 0:
-      return "continue";
+      return 1; // continue
   }
   j++;
   var z = 3;
@@ -29,37 +29,35 @@ var _loop2 = function () {
   });
 };
 for (i = 0; i < 10; i++) {
-  var _ret = _loop2();
-  if (_ret === "continue") continue;
+  if (_loop2()) continue;
 }
 expect(j).toBe(9);
 
 // it should work with loops nested within switch
 j = 0;
 var _loop3 = function () {
-  switch (i) {
-    case 0:
-      var _loop4 = function () {
-        var z = 3;
-        (function () {
-          return z;
-        });
-        j++;
-        return "break";
-      };
-      for (k = 0; k < 10; k++) {
-        var _ret2 = _loop4();
-        if (_ret2 === "break") break;
-      }
-      break;
-  }
-  var z = 3;
-  (function () {
-    return z;
-  });
-};
+    switch (i) {
+      case 0:
+        var _loop4 = function () {
+          var z = 3;
+          (function () {
+            return z;
+          });
+          j++;
+          return 1; // break
+        };
+        for (k = 0; k < 10; k++) {
+          if (_loop4()) break;
+        }
+        break;
+    }
+    var z = 3;
+    (function () {
+      return z;
+    });
+  },
+  k;
 for (i = 0; i < 10; i++) {
-  var k;
   _loop3();
 }
 expect(j).toBe(1);
diff --git a/...gin-transform-block-scoping/test/fixtures/general/closure-in-generator-or-async/output.js b/...gin-transform-block-scoping/test/fixtures/general/closure-in-generator-or-async/output.js
@@ -1,38 +1,38 @@
 function* a() {
   var _loop = function* () {
-    var x = yield "iteration";
-    fn = function () {
-      return x;
-    };
-  };
+      var x = yield "iteration";
+      fn = function () {
+        return x;
+      };
+    },
+    fn;
   do {
-    var fn;
     yield* _loop();
   } while (false);
   return fn;
 }
 async function b() {
   var _loop2 = async function () {
-    var x = await "iteration";
-    fn = function () {
-      return x;
-    };
-  };
+      var x = await "iteration";
+      fn = function () {
+        return x;
+      };
+    },
+    fn;
   do {
-    var fn;
     await _loop2();
   } while (false);
   return fn;
 }
 async function* c() {
   var _loop3 = async function* () {
-    var x = yield "iteration";
-    fn = function () {
-      return x;
-    };
-  };
+      var x = yield "iteration";
+      fn = function () {
+        return x;
+      };
+    },
+    fn;
   do {
-    var fn;
     yield* _loop3();
   } while (false);
   return fn;

diff --git a/...plugin-transform-block-scoping/test/fixtures/general/for-break-continue-closure/output.js b/...plugin-transform-block-scoping/test/fixtures/general/for-break-continue-closure/output.js
@@ -7,7 +7,7 @@ var _loop = function () {
           return b;
         });
         if (true) break;
-        return "continue";
+        return 1; // continue
       }
     case false:
       {
@@ -16,6 +16,5 @@ var _loop = function () {
   }
 };
 for (var a of [1]) {
-  var _ret = _loop();
-  if (_ret === "continue") continue;
+  if (_loop()) continue;
 }
diff --git a/...-plugin-transform-block-scoping/test/fixtures/general/for-break-continue-return/output.js b/...-plugin-transform-block-scoping/test/fixtures/general/for-break-continue-return/output.js
@@ -1,22 +1,23 @@
 (function () {
   var _loop = function (i) {
-    fns.push(function () {
-      return i;
-    });
-    if (i === 1) {
-      return "continue";
-    } else if (i === 2) {
-      return "break";
-    } else if (i === 3) {
-      return {
-        v: i
-      };
-    }
-  };
+      fns.push(function () {
+        return i;
+      });
+      if (i === 1) {
+        return 0; // continue
+      } else if (i === 2) {
+        return 1; // break
+      } else if (i === 3) {
+        return {
+          v: i
+        };
+      }
+    },
+    _ret;
   for (var i in nums) {
-    var _ret = _loop(i);
-    if (_ret === "continue") continue;
-    if (_ret === "break") break;
-    if (typeof _ret === "object") return _ret.v;
+    _ret = _loop(i);
+    if (_ret === 0) continue;
+    if (_ret === 1) break;
+    if (_ret) return _ret.v;
   }
 })();
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/for-break/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/for-break/output.js
@@ -2,9 +2,8 @@ var _loop = function (i) {
   fns.push(function () {
     return i;
   });
-  return "break";
+  return 1; // break
 };
 for (var i in nums) {
-  var _ret = _loop(i);
-  if (_ret === "break") break;
+  if (_loop(i)) break;
 }
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/for-continue/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/for-continue/output.js
@@ -2,9 +2,8 @@ var _loop = function (i) {
   fns.push(function () {
     return i;
   });
-  return "continue";
+  return 1; // continue
 };
 for (var i in nums) {
-  var _ret = _loop(i);
-  if (_ret === "continue") continue;
+  if (_loop(i)) continue;
 }
diff --git a/...babel-plugin-transform-block-scoping/test/fixtures/general/for-return-undefined/output.js b/...babel-plugin-transform-block-scoping/test/fixtures/general/for-return-undefined/output.js
@@ -1,14 +1,15 @@
 (function () {
   var _loop = function (i) {
-    fns.push(function () {
-      return i;
-    });
-    return {
-      v: void 0
-    };
-  };
+      fns.push(function () {
+        return i;
+      });
+      return {
+        v: void 0
+      };
+    },
+    _ret;
   for (var i in nums) {
-    var _ret = _loop(i);
-    if (typeof _ret === "object") return _ret.v;
+    _ret = _loop(i);
+    if (_ret) return _ret.v;
   }
 })();
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/for-return/output.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/for-return/output.js
@@ -1,14 +1,15 @@
 (function () {
   var _loop = function (i) {
-    fns.push(function () {
-      return i;
-    });
-    return {
-      v: i
-    };
-  };
+      fns.push(function () {
+        return i;
+      });
+      return {
+        v: i
+      };
+    },
+    _ret;
   for (var i in nums) {
-    var _ret = _loop(i);
-    if (typeof _ret === "object") return _ret.v;
+    _ret = _loop(i);
+    if (_ret) return _ret.v;
   }
 })();