Parse async do expressions

packages/babel-core/src/parser/util/missing-plugin-helper.ts

@@ -1,4 +1,10 @@
 const pluginNameMap = {
+  asyncDoExpressions: {
+    syntax: {
+      name: "@babel/plugin-syntax-async-do-expressions",
+      url: "https://git.io/JYer8",
+    },
+  },
   classProperties: {
     syntax: {
       name: "@babel/plugin-syntax-class-properties",

packages/babel-generator/src/generators/expressions.ts

@@ -20,6 +20,10 @@ export function UnaryExpression(this: Printer, node: t.UnaryExpression) {
 }
 
 export function DoExpression(this: Printer, node: t.DoExpression) {
+  if (node.async) {
+    this.word("async");
+    this.space();
+  }
   this.word("do");
   this.space();
   this.print(node.body, node);

packages/babel-generator/src/node/parentheses.ts

@@ -82,7 +82,8 @@ export function DoExpression(
   parent: any,
   printStack: Array<any>,
 ): boolean {
-  return isFirstInStatement(printStack);
+  // `async do` can start an expression statement
+  return !node.async && isFirstInStatement(printStack);
 }
 
 export function Binary(node: any, parent: any): boolean {

packages/babel-generator/test/fixtures/async-do-expressions/basic/input.js

@@ -0,0 +1,5 @@
+async do {
+  1;
+};
+
+(async do {});

packages/babel-generator/test/fixtures/async-do-expressions/basic/output.js

@@ -0,0 +1,4 @@
+async do {
+  1;
+};
+async do {};

packages/babel-generator/test/fixtures/async-do-expressions/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["asyncDoExpressions", "doExpressions"]
+}

packages/babel-generator/test/fixtures/async-do-expressions/retain-lines/input.js

@@ -0,0 +1,3 @@
+/* leading comments
+*/async do
+{ 1 } + 0;

packages/babel-generator/test/fixtures/async-do-expressions/retain-lines/options.json

@@ -0,0 +1,3 @@
+{
+  "retainLines": true
+}

packages/babel-generator/test/fixtures/async-do-expressions/retain-lines/output.js

@@ -0,0 +1,3 @@
+/* leading comments
+*/async do
+{1;} + 0;

packages/babel-parser/ast/spec.md

@@ -1084,6 +1084,7 @@ An expression wrapped by parentheses. By default `@babel/parser` does not create
 interface DoExpression <: Expression {
   type: "DoExpression";
   body: BlockStatement;
+  async: boolean;
 }
 ```
 

packages/babel-parser/src/parser/expression.js

@@ -1033,6 +1033,8 @@ export default class ExpressionParser extends LValParser {
             );
           } else if (this.match(tt.name)) {
             return this.parseAsyncArrowUnaryFunction(id);
+          } else if (this.match(tt._do)) {
+            return this.parseDo(true);
           }
         }
 
@@ -1049,7 +1051,7 @@ export default class ExpressionParser extends LValParser {
       }
 
       case tt._do: {
-        return this.parseDo();
+        return this.parseDo(false);
       }
 
       case tt.regexp: {
@@ -1231,13 +1233,27 @@ export default class ExpressionParser extends LValParser {
   }
 
   // https://github.com/tc39/proposal-do-expressions
-  parseDo(): N.DoExpression {
+  // https://github.com/tc39/proposal-async-do-expressions
+  parseDo(isAsync: boolean): N.DoExpression {
     this.expectPlugin("doExpressions");
+    if (isAsync) {
+      this.expectPlugin("asyncDoExpressions");
+    }
     const node = this.startNode();
+    node.async = isAsync;
     this.next(); // eat `do`
     const oldLabels = this.state.labels;
     this.state.labels = [];
-    node.body = this.parseBlock();
+    if (isAsync) {
+      // AsyncDoExpression :
+      // async [no LineTerminator here] do Block[~Yield, +Await, ~Return]
+      this.prodParam.enter(PARAM_AWAIT);
+      node.body = this.parseBlock();
+      this.prodParam.exit();
+    } else {
+      node.body = this.parseBlock();
+    }
+
     this.state.labels = oldLabels;
     return this.finishNode(node, "DoExpression");
   }

packages/babel-parser/src/plugin-utils.js

@@ -117,6 +117,18 @@ export function validatePlugins(plugins: PluginList) {
         RECORD_AND_TUPLE_SYNTAX_TYPES.map(p => `'${p}'`).join(", "),
     );
   }
+
+  if (
+    hasPlugin(plugins, "asyncDoExpressions") &&
+    !hasPlugin(plugins, "doExpressions")
+  ) {
+    const error = new Error(
+      "'asyncDoExpressions' requires 'doExpressions', please add 'doExpressions' to parser plugins.",
+    );
+    // $FlowIgnore
+    error.missingPlugins = "doExpressions"; // so @babel/core can provide better error message
+    throw error;
+  }
 }
 
 // These plugins are defined using a mixin which extends the parser class.

packages/babel-parser/src/types.js

@@ -402,6 +402,7 @@ export type ArrayExpression = NodeBase & {
 export type DoExpression = NodeBase & {
   type: "DoExpression",
   body: ?BlockStatement,
+  async: boolean,
 };
 
 export type TupleExpression = NodeBase & {

packages/babel-parser/test/fixtures/experimental/_no-plugin/async-do-expressions-with-do-expressions/input.js

@@ -0,0 +1 @@
+(async do {x})

packages/babel-parser/test/fixtures/experimental/_no-plugin/async-do-expressions-with-do-expressions/options.json

@@ -0,0 +1,6 @@
+{
+  "throws": "This experimental syntax requires enabling the parser plugin: 'asyncDoExpressions' (1:7)",
+  "plugins": [
+    "doExpressions"
+  ]
+}

packages/babel-parser/test/fixtures/experimental/_no-plugin/async-do-expressions/input.js

@@ -0,0 +1 @@
+(async do {x})

packages/babel-parser/test/fixtures/experimental/_no-plugin/async-do-expressions/options.json

@@ -0,0 +1,4 @@
+{
+  "throws": "This experimental syntax requires enabling the parser plugin: 'doExpressions' (1:7)",
+  "plugins": []
+}

packages/babel-parser/test/fixtures/experimental/async-do-expressions/asi-async-and-do-while/input.js

@@ -0,0 +1,5 @@
+async
+do {
+  42
+}
+while (false);

packages/babel-parser/test/fixtures/experimental/async-do-expressions/asi-async-and-do-while/output.json

@@ -0,0 +1,51 @@
+{
+  "type": "File",
+  "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":14}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":14}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5}},
+        "expression": {
+          "type": "Identifier",
+          "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5},"identifierName":"async"},
+          "name": "async"
+        }
+      },
+      {
+        "type": "DoWhileStatement",
+        "start":6,"end":32,"loc":{"start":{"line":2,"column":0},"end":{"line":5,"column":14}},
+        "body": {
+          "type": "BlockStatement",
+          "start":9,"end":17,"loc":{"start":{"line":2,"column":3},"end":{"line":4,"column":1}},
+          "body": [
+            {
+              "type": "ExpressionStatement",
+              "start":13,"end":15,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":4}},
+              "expression": {
+                "type": "NumericLiteral",
+                "start":13,"end":15,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":4}},
+                "extra": {
+                  "rawValue": 42,
+                  "raw": "42"
+                },
+                "value": 42
+              }
+            }
+          ],
+          "directives": []
+        },
+        "test": {
+          "type": "BooleanLiteral",
+          "start":25,"end":30,"loc":{"start":{"line":5,"column":7},"end":{"line":5,"column":12}},
+          "value": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/async-do-expressions/asi-async-do-and-while/input.js

@@ -0,0 +1,4 @@
+async do {
+  42
+}
+while (false);

packages/babel-parser/test/fixtures/experimental/async-do-expressions/asi-async-do-and-while/output.json

@@ -0,0 +1,55 @@
+{
+  "type": "File",
+  "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":14}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":4,"column":14}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":17,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "expression": {
+          "type": "DoExpression",
+          "start":6,"end":17,"loc":{"start":{"line":1,"column":6},"end":{"line":3,"column":1}},
+          "async": true,
+          "body": {
+            "type": "BlockStatement",
+            "start":9,"end":17,"loc":{"start":{"line":1,"column":9},"end":{"line":3,"column":1}},
+            "body": [
+              {
+                "type": "ExpressionStatement",
+                "start":13,"end":15,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "expression": {
+                  "type": "NumericLiteral",
+                  "start":13,"end":15,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                  "extra": {
+                    "rawValue": 42,
+                    "raw": "42"
+                  },
+                  "value": 42
+                }
+              }
+            ],
+            "directives": []
+          }
+        }
+      },
+      {
+        "type": "WhileStatement",
+        "start":18,"end":32,"loc":{"start":{"line":4,"column":0},"end":{"line":4,"column":14}},
+        "test": {
+          "type": "BooleanLiteral",
+          "start":25,"end":30,"loc":{"start":{"line":4,"column":7},"end":{"line":4,"column":12}},
+          "value": false
+        },
+        "body": {
+          "type": "EmptyStatement",
+          "start":31,"end":32,"loc":{"start":{"line":4,"column":13},"end":{"line":4,"column":14}}
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/async-do-expressions/asi/input.js

@@ -0,0 +1,4 @@
+async
+do {
+  42
+}

packages/babel-parser/test/fixtures/experimental/async-do-expressions/asi/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Unexpected token, expected \"while\" (4:1)"
+}

packages/babel-parser/test/fixtures/experimental/async-do-expressions/conditional-statement/input.js

@@ -0,0 +1,5 @@
+let x = async do {
+  if (foo()) { f() }
+  else if (bar()) { g() }
+  else { h() }
+};