From c376be7eabd6c3790024a0991512b3986535e707 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Thu, 10 Jun 2021 09:40:45 -0400
Subject: [PATCH] fix: disallow JSX tag after non-null assertion

---
 .../src/plugins/typescript/index.js           |  4 ++
 .../null-assertion-and-relational/input.ts    |  1 +
 .../options.json                              |  4 ++
 .../null-assertion-and-relational/output.json | 60 +++++++++++++++++++
 4 files changed, 69 insertions(+)
 create mode 100644 packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/input.ts
 create mode 100644 packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/options.json
 create mode 100644 packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/output.json

diff --git a/packages/babel-parser/src/plugins/typescript/index.js b/packages/babel-parser/src/plugins/typescript/index.js
index 78a7f20283fc..9f13c3704a83 100644
--- a/packages/babel-parser/src/plugins/typescript/index.js
+++ b/packages/babel-parser/src/plugins/typescript/index.js
@@ -2043,6 +2043,10 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       state: N.ParseSubscriptState,
     ): N.Expression {
       if (!this.hasPrecedingLineBreak() && this.match(tt.bang)) {
+        // When ! is consumed as a postfix operator (non-null assertion),
+        // disallow JSX tag forming after. e.g. When parsing `p! < n.p!`
+        // `<n.p` can not be a start of JSX tag
+        this.state.exprAllowed = false;
         this.next();
 
         const nonNullExpression: N.TsNonNullExpression = this.startNodeAt(
diff --git a/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/input.ts b/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/input.ts
new file mode 100644
index 000000000000..d60cf58b1430
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/input.ts
@@ -0,0 +1 @@
+x.v! < y.v!;
diff --git a/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/options.json b/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/options.json
new file mode 100644
index 000000000000..a0f82d16f05f
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/options.json
@@ -0,0 +1,4 @@
+{
+  "sourceType": "module",
+  "plugins": ["typescript", "jsx"]
+}
diff --git a/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/output.json b/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/output.json
new file mode 100644
index 000000000000..fd45a942f01e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/typescript/cast/null-assertion-and-relational/output.json
@@ -0,0 +1,60 @@
+{
+  "type": "File",
+  "start":0,"end":12,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":12}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":12,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":12}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start":0,"end":12,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":12}},
+        "expression": {
+          "type": "BinaryExpression",
+          "start":0,"end":11,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":11}},
+          "left": {
+            "type": "TSNonNullExpression",
+            "start":0,"end":4,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":4}},
+            "expression": {
+              "type": "MemberExpression",
+              "start":0,"end":3,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":3}},
+              "object": {
+                "type": "Identifier",
+                "start":0,"end":1,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":1},"identifierName":"x"},
+                "name": "x"
+              },
+              "computed": false,
+              "property": {
+                "type": "Identifier",
+                "start":2,"end":3,"loc":{"start":{"line":1,"column":2},"end":{"line":1,"column":3},"identifierName":"v"},
+                "name": "v"
+              }
+            }
+          },
+          "operator": "<",
+          "right": {
+            "type": "TSNonNullExpression",
+            "start":7,"end":11,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":11}},
+            "expression": {
+              "type": "MemberExpression",
+              "start":7,"end":10,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":10}},
+              "object": {
+                "type": "Identifier",
+                "start":7,"end":8,"loc":{"start":{"line":1,"column":7},"end":{"line":1,"column":8},"identifierName":"y"},
+                "name": "y"
+              },
+              "computed": false,
+              "property": {
+                "type": "Identifier",
+                "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10},"identifierName":"v"},
+                "name": "v"
+              }
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file