From 61ec5ce95791ff88203b4015b16a84f6583e3fa0 Mon Sep 17 00:00:00 2001
From: Dennis Czombera <milchschaumschluerfer@gmail.com>
Date: Fri, 13 Apr 2018 00:07:41 +0200
Subject: [PATCH] Provide better error message for invalid default export
 declaration (#7717)

---
 packages/babylon/src/parser/statement.js      |   9 ++
 .../export-default-class-declaration/input.js |   1 +
 .../output.json                               |  98 +++++++++++++++++
 .../export-default-class-expression/input.js  |   1 +
 .../output.json                               | 102 ++++++++++++++++++
 .../input.js                                  |   3 +
 .../options.json                              |   3 +
 .../input.js                                  |   3 +
 .../options.json                              |   3 +
 .../input.js                                  |   3 +
 .../options.json                              |   3 +
 11 files changed, 229 insertions(+)
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/input.js
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/output.json
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/input.js
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/output.json
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/input.js
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/options.json
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/input.js
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/options.json
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/input.js
 create mode 100644 packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/options.json

diff --git a/packages/babylon/src/parser/statement.js b/packages/babylon/src/parser/statement.js
index 68f9cd0d75..8919221897 100644
--- a/packages/babylon/src/parser/statement.js
+++ b/packages/babylon/src/parser/statement.js
@@ -1417,6 +1417,15 @@ export default class StatementParser extends ExpressionParser {
     } else if (this.match(tt.at)) {
       this.parseDecorators(false);
       return this.parseClass(expr, true, true);
+    } else if (
+      this.match(tt._let) ||
+      this.match(tt._const) ||
+      this.match(tt._var)
+    ) {
+      this.raise(
+        this.state.start,
+        "Only expressions, functions or classes are allowed as the `default` export.",
+      );
     } else {
       const res = this.parseMaybeAssign();
       this.semicolon();
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/input.js b/packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/input.js
new file mode 100644
index 0000000000..7804111002
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/input.js
@@ -0,0 +1 @@
+export default class Foo {}
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/output.json b/packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/output.json
new file mode 100644
index 0000000000..ed3482551f
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-class-declaration/output.json
@@ -0,0 +1,98 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 27,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 27
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 27,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 27
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "ExportDefaultDeclaration",
+        "start": 0,
+        "end": 27,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 27
+          }
+        },
+        "declaration": {
+          "type": "ClassDeclaration",
+          "start": 15,
+          "end": 27,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 15
+            },
+            "end": {
+              "line": 1,
+              "column": 27
+            }
+          },
+          "id": {
+            "type": "Identifier",
+            "start": 21,
+            "end": 24,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 21
+              },
+              "end": {
+                "line": 1,
+                "column": 24
+              },
+              "identifierName": "Foo"
+            },
+            "name": "Foo"
+          },
+          "superClass": null,
+          "body": {
+            "type": "ClassBody",
+            "start": 25,
+            "end": 27,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 25
+              },
+              "end": {
+                "line": 1,
+                "column": 27
+              }
+            },
+            "body": []
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/input.js b/packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/input.js
new file mode 100644
index 0000000000..caaf4f896e
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/input.js
@@ -0,0 +1 @@
+export default (class Foo {});
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/output.json b/packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/output.json
new file mode 100644
index 0000000000..a5cf3095a9
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-class-expression/output.json
@@ -0,0 +1,102 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 30,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 30
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 30,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 30
+      }
+    },
+    "sourceType": "module",
+    "body": [
+      {
+        "type": "ExportDefaultDeclaration",
+        "start": 0,
+        "end": 30,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 30
+          }
+        },
+        "declaration": {
+          "type": "ClassExpression",
+          "start": 16,
+          "end": 28,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 16
+            },
+            "end": {
+              "line": 1,
+              "column": 28
+            }
+          },
+          "id": {
+            "type": "Identifier",
+            "start": 22,
+            "end": 25,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 22
+              },
+              "end": {
+                "line": 1,
+                "column": 25
+              },
+              "identifierName": "Foo"
+            },
+            "name": "Foo"
+          },
+          "superClass": null,
+          "body": {
+            "type": "ClassBody",
+            "start": 26,
+            "end": 28,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 26
+              },
+              "end": {
+                "line": 1,
+                "column": 28
+              }
+            },
+            "body": []
+          },
+          "extra": {
+            "parenthesized": true,
+            "parenStart": 15
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/input.js b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/input.js
new file mode 100644
index 0000000000..945b019ea1
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/input.js
@@ -0,0 +1,3 @@
+export default const Foo = () => {
+    return `<div class="bar">Hola</div>`;
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/options.json b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/options.json
new file mode 100644
index 0000000000..371aabd618
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration/options.json
@@ -0,0 +1,3 @@
+{
+    "throws": "Only expressions, functions or classes are allowed as the `default` export. (1:15)"
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/input.js b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/input.js
new file mode 100644
index 0000000000..b186094605
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/input.js
@@ -0,0 +1,3 @@
+export default let Foo = () => {
+    return `<div class="bar">Hola</div>`;
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/options.json b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/options.json
new file mode 100644
index 0000000000..371aabd618
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration2/options.json
@@ -0,0 +1,3 @@
+{
+    "throws": "Only expressions, functions or classes are allowed as the `default` export. (1:15)"
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/input.js b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/input.js
new file mode 100644
index 0000000000..03791d0e9e
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/input.js
@@ -0,0 +1,3 @@
+export default var Foo = () => {
+    return `<div class="bar">Hola</div>`;
+}
\ No newline at end of file
diff --git a/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/options.json b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/options.json
new file mode 100644
index 0000000000..371aabd618
--- /dev/null
+++ b/packages/babylon/test/fixtures/es2015/modules/export-default-variable-declaration3/options.json
@@ -0,0 +1,3 @@
+{
+    "throws": "Only expressions, functions or classes are allowed as the `default` export. (1:15)"
+}
\ No newline at end of file