From b7a1ed072d9defc90a60c2feec91979ba626f0e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jochen=20K=C3=BChner?= <jochen.kuehner@gmx.de>
Date: Tue, 2 Nov 2021 18:42:10 +0100
Subject: [PATCH] Fix parsing error in exponent expressions with unary
 left-hand sides (#201)

* Fix parsing error in exponent expressions with unary left-hand sides.

Esprima (correctly) rejects expressions like -1**2. - https://github.com/jquery/esprima/pull/2070
However, expressions like (-1)**2 are valid but still rejected.
This commit fixes this issue by identifying when the left operand
is parenthesized.

Fixes https://github.com/jquery/esprima/issues/1981

* add test for unary left side
---
 src/Esprima/JavascriptParser.cs               |  12 +-
 .../invalid-syntax/unary_left_side.js         |   1 +
 .../invalid-syntax/unary_left_side.tree.json  | 112 ++++++++++++++++++
 3 files changed, 121 insertions(+), 4 deletions(-)
 create mode 100644 test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.js
 create mode 100644 test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.tree.json

diff --git a/src/Esprima/JavascriptParser.cs b/src/Esprima/JavascriptParser.cs
index 3f030d5b..0c110d1e 100644
--- a/src/Esprima/JavascriptParser.cs
+++ b/src/Esprima/JavascriptParser.cs
@@ -1861,10 +1861,14 @@ private Expression ParseUnaryExpression()
 
         private Expression ParseExponentiationExpression()
         {
-            var startToken = _lookahead;
-
-            var expr = InheritCoverGrammar(parseUnaryExpression);
-            if (expr.Type != Nodes.UnaryExpression && Match("**"))
+            var startToken = _lookahead;
+
+            var isLeftParenthesized = this.Match("(");
+            var expr = InheritCoverGrammar(parseUnaryExpression);
+
+            var exponentAllowed = expr.Type != Nodes.UnaryExpression || isLeftParenthesized;
+
+            if (exponentAllowed && Match("**"))
             {
                 NextToken();
                 _context.IsAssignmentTarget = false;
diff --git a/test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.js b/test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.js
new file mode 100644
index 00000000..ec7c4647
--- /dev/null
+++ b/test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.js
@@ -0,0 +1 @@
+(+2)**4;
\ No newline at end of file
diff --git a/test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.tree.json b/test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.tree.json
new file mode 100644
index 00000000..ee247cad
--- /dev/null
+++ b/test/Esprima.Tests/Fixtures/invalid-syntax/unary_left_side.tree.json
@@ -0,0 +1,112 @@
+{
+  "type": "Program",
+  "body": [
+    {
+      "type": "ExpressionStatement",
+      "expression": {
+        "type": "BinaryExpression",
+        "operator": "**",
+        "left": {
+          "type": "UnaryExpression",
+          "operator": "+",
+          "argument": {
+            "type": "Literal",
+            "value": 2,
+            "raw": "2",
+            "range": [
+              2,
+              3
+            ],
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 2
+              },
+              "end": {
+                "line": 1,
+                "column": 3
+              }
+            }
+          },
+          "prefix": true,
+          "range": [
+            1,
+            3
+          ],
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 1
+            },
+            "end": {
+              "line": 1,
+              "column": 3
+            }
+          }
+        },
+        "right": {
+          "type": "Literal",
+          "value": 4,
+          "raw": "4",
+          "range": [
+            6,
+            7
+          ],
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 6
+            },
+            "end": {
+              "line": 1,
+              "column": 7
+            }
+          }
+        },
+        "range": [
+          0,
+          7
+        ],
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 7
+          }
+        }
+      },
+      "range": [
+        0,
+        8
+      ],
+      "loc": {
+        "start": {
+          "line": 1,
+          "column": 0
+        },
+        "end": {
+          "line": 1,
+          "column": 8
+        }
+      }
+    }
+  ],
+  "sourceType": "script",
+  "range": [
+    0,
+    8
+  ],
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 8
+    }
+  }
+}
\ No newline at end of file