Under jsx: preserve, actually preserve expressions which contain only comments

src/compiler/emitter.ts

@@ -2824,7 +2824,8 @@ namespace ts {
             }
             pos = writeTokenText(token, writer, pos);
             if (isSimilarNode && contextNode.end !== pos) {
-                emitTrailingCommentsOfPosition(pos, /*prefixSpace*/ true);
+                const isJsxExprContex = contextNode.kind === SyntaxKind.JsxExpression;
+                emitTrailingCommentsOfPosition(pos, /*prefixSpace*/ !isJsxExprContex, /*forceNoNewline*/ isJsxExprContex);
             }
             return pos;
         }
@@ -3378,8 +3379,8 @@ namespace ts {
         }
 
         function emitJsxExpression(node: JsxExpression) {
-            if (node.expression) {
-                writePunctuation("{");
+            if (node.expression || (!commentsDisabled && !nodeIsSynthesized(node) && getTextOfNode(node).length > 2 && getTextOfNode(node).indexOf("/*") > -1)) { // preserve empty expressions if they contain comments!
+                emitTokenWithComment(SyntaxKind.OpenBraceToken, node.pos, writePunctuation, node);
                 emit(node.dotDotDotToken);
                 emitExpression(node.expression);
                 writePunctuation("}");
@@ -5230,21 +5231,25 @@ namespace ts {
             }
         }
 
-        function emitTrailingCommentsOfPosition(pos: number, prefixSpace?: boolean) {
+        function emitTrailingCommentsOfPosition(pos: number, prefixSpace?: boolean, forceNoNewline?: boolean) {
             if (commentsDisabled) {
                 return;
             }
             enterComment();
-            forEachTrailingCommentToEmit(pos, prefixSpace ? emitTrailingComment : emitTrailingCommentOfPosition);
+            forEachTrailingCommentToEmit(pos, prefixSpace ? emitTrailingComment : forceNoNewline ? emitTrailingCommentOfPositionNoNewline : emitTrailingCommentOfPosition);
             exitComment();
         }
 
-        function emitTrailingCommentOfPosition(commentPos: number, commentEnd: number, _kind: SyntaxKind, hasTrailingNewLine: boolean) {
+        function emitTrailingCommentOfPositionNoNewline(commentPos: number, commentEnd: number) {
             // trailing comments of a position are emitted at /*trailing comment1 */space/*trailing comment*/space
 
             emitPos(commentPos);
             writeCommentRange(currentSourceFile!.text, getCurrentLineMap(), writer, commentPos, commentEnd, newLine);
             emitPos(commentEnd);
+        }
+
+        function emitTrailingCommentOfPosition(commentPos: number, commentEnd: number, _kind: SyntaxKind, hasTrailingNewLine: boolean) {
+            emitTrailingCommentOfPositionNoNewline(commentPos, commentEnd);
 
             if (hasTrailingNewLine) {
                 writer.writeLine();

src/compiler/transformers/module/module.ts

@@ -1790,7 +1790,7 @@ namespace ts {
                         const name = importDeclaration.propertyName || importDeclaration.name;
                         return setTextRange(
                             factory.createPropertyAccessExpression(
-                                factory.getGeneratedNameForNode(importDeclaration.parent.parent.parent),
+                                factory.getGeneratedNameForNode(importDeclaration.parent?.parent?.parent || importDeclaration),
                                 factory.cloneNode(name)
                             ),
                             /*location*/ node

src/compiler/transformers/module/system.ts

@@ -1678,7 +1678,7 @@ namespace ts {
                             factory.createPropertyAssignment(
                                 factory.cloneNode(name),
                                 factory.createPropertyAccessExpression(
-                                    factory.getGeneratedNameForNode(importDeclaration.parent.parent.parent),
+                                    factory.getGeneratedNameForNode(importDeclaration.parent?.parent?.parent || importDeclaration),
                                     factory.cloneNode(importDeclaration.propertyName || importDeclaration.name)
                                 ),
                             ),
@@ -1747,7 +1747,7 @@ namespace ts {
                     else if (isImportSpecifier(importDeclaration)) {
                         return setTextRange(
                             factory.createPropertyAccessExpression(
-                                factory.getGeneratedNameForNode(importDeclaration.parent.parent.parent),
+                                factory.getGeneratedNameForNode(importDeclaration.parent?.parent?.parent || importDeclaration),
                                 factory.cloneNode(importDeclaration.propertyName || importDeclaration.name)
                             ),
                             /*location*/ node

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=preserve,module=commonjs).js

@@ -0,0 +1,27 @@
+//// [commentsOnJSXExpressionsArePreserved.tsx]
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+    type JSXElement = any;
+}
+class Component {
+    render() {
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}
+
+//// [commentsOnJSXExpressionsArePreserved.jsx]
+var Component = /** @class */ (function () {
+    function Component() {
+    }
+    Component.prototype.render = function () {
+        return <div>
+            {/* missing */}
+            {null /* preserved */}
+        </div>;
+    };
+    return Component;
+}());

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=preserve,module=commonjs).symbols

@@ -0,0 +1,24 @@
+=== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx ===
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+>JSX : Symbol(JSX, Decl(commentsOnJSXExpressionsArePreserved.tsx, 0, 0))
+
+    interface IntrsinsicElements { [index: string]: any }
+>IntrsinsicElements : Symbol(IntrsinsicElements, Decl(commentsOnJSXExpressionsArePreserved.tsx, 1, 15))
+>index : Symbol(index, Decl(commentsOnJSXExpressionsArePreserved.tsx, 2, 36))
+
+    type JSXElement = any;
+>JSXElement : Symbol(JSXElement, Decl(commentsOnJSXExpressionsArePreserved.tsx, 2, 57))
+}
+class Component {
+>Component : Symbol(Component, Decl(commentsOnJSXExpressionsArePreserved.tsx, 4, 1))
+
+    render() {
+>render : Symbol(Component.render, Decl(commentsOnJSXExpressionsArePreserved.tsx, 5, 17))
+
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=preserve,module=commonjs).types

@@ -0,0 +1,27 @@
+=== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx ===
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+>index : string
+
+    type JSXElement = any;
+>JSXElement : any
+}
+class Component {
+>Component : Component
+
+    render() {
+>render : () => any
+
+        return <div>
+><div>            {/* missing */}            {null/* preserved */}        </div> : error
+>div : any
+
+            {/* missing */}
+            {null/* preserved */}
+>null : null
+
+        </div>;
+>div : any
+    }
+}

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=preserve,module=system).js

@@ -0,0 +1,27 @@
+//// [commentsOnJSXExpressionsArePreserved.tsx]
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+    type JSXElement = any;
+}
+class Component {
+    render() {
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}
+
+//// [commentsOnJSXExpressionsArePreserved.jsx]
+var Component = /** @class */ (function () {
+    function Component() {
+    }
+    Component.prototype.render = function () {
+        return <div>
+            {/* missing */}
+            {null /* preserved */}
+        </div>;
+    };
+    return Component;
+}());

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=preserve,module=system).symbols

@@ -0,0 +1,24 @@
+=== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx ===
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+>JSX : Symbol(JSX, Decl(commentsOnJSXExpressionsArePreserved.tsx, 0, 0))
+
+    interface IntrsinsicElements { [index: string]: any }
+>IntrsinsicElements : Symbol(IntrsinsicElements, Decl(commentsOnJSXExpressionsArePreserved.tsx, 1, 15))
+>index : Symbol(index, Decl(commentsOnJSXExpressionsArePreserved.tsx, 2, 36))
+
+    type JSXElement = any;
+>JSXElement : Symbol(JSXElement, Decl(commentsOnJSXExpressionsArePreserved.tsx, 2, 57))
+}
+class Component {
+>Component : Symbol(Component, Decl(commentsOnJSXExpressionsArePreserved.tsx, 4, 1))
+
+    render() {
+>render : Symbol(Component.render, Decl(commentsOnJSXExpressionsArePreserved.tsx, 5, 17))
+
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=preserve,module=system).types

@@ -0,0 +1,27 @@
+=== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx ===
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+>index : string
+
+    type JSXElement = any;
+>JSXElement : any
+}
+class Component {
+>Component : Component
+
+    render() {
+>render : () => any
+
+        return <div>
+><div>            {/* missing */}            {null/* preserved */}        </div> : error
+>div : any
+
+            {/* missing */}
+            {null/* preserved */}
+>null : null
+
+        </div>;
+>div : any
+    }
+}

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=react,module=commonjs).errors.txt

@@ -0,0 +1,19 @@
+tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx(8,17): error TS2304: Cannot find name 'React'.
+
+
+==== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx (1 errors) ====
+    // file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+    namespace JSX {
+        interface IntrsinsicElements { [index: string]: any }
+        type JSXElement = any;
+    }
+    class Component {
+        render() {
+            return <div>
+                    ~~~
+!!! error TS2304: Cannot find name 'React'.
+                {/* missing */}
+                {null/* preserved */}
+            </div>;
+        }
+    }

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=react,module=commonjs).js

@@ -0,0 +1,24 @@
+//// [commentsOnJSXExpressionsArePreserved.tsx]
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+    type JSXElement = any;
+}
+class Component {
+    render() {
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}
+
+//// [commentsOnJSXExpressionsArePreserved.js]
+var Component = /** @class */ (function () {
+    function Component() {
+    }
+    Component.prototype.render = function () {
+        return React.createElement("div", null, null /* preserved */);
+    };
+    return Component;
+}());

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=react,module=commonjs).symbols

@@ -0,0 +1,24 @@
+=== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx ===
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+>JSX : Symbol(JSX, Decl(commentsOnJSXExpressionsArePreserved.tsx, 0, 0))
+
+    interface IntrsinsicElements { [index: string]: any }
+>IntrsinsicElements : Symbol(IntrsinsicElements, Decl(commentsOnJSXExpressionsArePreserved.tsx, 1, 15))
+>index : Symbol(index, Decl(commentsOnJSXExpressionsArePreserved.tsx, 2, 36))
+
+    type JSXElement = any;
+>JSXElement : Symbol(JSXElement, Decl(commentsOnJSXExpressionsArePreserved.tsx, 2, 57))
+}
+class Component {
+>Component : Symbol(Component, Decl(commentsOnJSXExpressionsArePreserved.tsx, 4, 1))
+
+    render() {
+>render : Symbol(Component.render, Decl(commentsOnJSXExpressionsArePreserved.tsx, 5, 17))
+
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=react,module=commonjs).types

@@ -0,0 +1,27 @@
+=== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx ===
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+>index : string
+
+    type JSXElement = any;
+>JSXElement : any
+}
+class Component {
+>Component : Component
+
+    render() {
+>render : () => any
+
+        return <div>
+><div>            {/* missing */}            {null/* preserved */}        </div> : any
+>div : any
+
+            {/* missing */}
+            {null/* preserved */}
+>null : null
+
+        </div>;
+>div : any
+    }
+}

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=react,module=system).errors.txt

@@ -0,0 +1,19 @@
+tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx(8,17): error TS2304: Cannot find name 'React'.
+
+
+==== tests/cases/compiler/commentsOnJSXExpressionsArePreserved.tsx (1 errors) ====
+    // file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+    namespace JSX {
+        interface IntrsinsicElements { [index: string]: any }
+        type JSXElement = any;
+    }
+    class Component {
+        render() {
+            return <div>
+                    ~~~
+!!! error TS2304: Cannot find name 'React'.
+                {/* missing */}
+                {null/* preserved */}
+            </div>;
+        }
+    }

tests/baselines/reference/commentsOnJSXExpressionsArePreserved(jsx=react,module=system).js

@@ -0,0 +1,24 @@
+//// [commentsOnJSXExpressionsArePreserved.tsx]
+// file is interntionally not a module - this tests for a crash in the module/system transforms alongside the `react-jsx` and `react-jsxdev` outputs
+namespace JSX {
+    interface IntrsinsicElements { [index: string]: any }
+    type JSXElement = any;
+}
+class Component {
+    render() {
+        return <div>
+            {/* missing */}
+            {null/* preserved */}
+        </div>;
+    }
+}
+
+//// [commentsOnJSXExpressionsArePreserved.js]
+var Component = /** @class */ (function () {
+    function Component() {
+    }
+    Component.prototype.render = function () {
+        return React.createElement("div", null, null /* preserved */);
+    };
+    return Component;
+}());