(fluent) Enforce the default variant during parsing

Author: stasm

fluent-syntax/test/fixtures_structure/select_expressions.ftl

@@ -0,0 +1,9 @@
+# ERROR No blanks are allowed between * and [.
+err01 = { $sel ->
+    *  [key] Value
+}
+
+# ERROR Missing default variant.
+err02 = { $sel ->
+    [key] Value
+}

fluent-syntax/test/fixtures_structure/select_expressions.json

@@ -0,0 +1,72 @@
+{
+  "type": "Resource",
+  "body": [
+    {
+      "type": "Comment",
+      "content": "ERROR No blanks are allowed between * and [.",
+      "span": {
+        "type": "Span",
+        "start": 0,
+        "end": 46
+      }
+    },
+    {
+      "type": "Junk",
+      "annotations": [
+        {
+          "type": "Annotation",
+          "code": "E0011",
+          "args": [],
+          "message": "Expected at least one variant after \"->\"",
+          "span": {
+            "type": "Span",
+            "start": 69,
+            "end": 69
+          }
+        }
+      ],
+      "content": "err01 = { $sel ->\n    *  [key] Value\n}\n\n",
+      "span": {
+        "type": "Span",
+        "start": 47,
+        "end": 87
+      }
+    },
+    {
+      "type": "Comment",
+      "content": "ERROR Missing default variant.",
+      "span": {
+        "type": "Span",
+        "start": 87,
+        "end": 119
+      }
+    },
+    {
+      "type": "Junk",
+      "annotations": [
+        {
+          "type": "Annotation",
+          "code": "E0010",
+          "args": [],
+          "message": "Expected one of the variants to be marked as default (*)",
+          "span": {
+            "type": "Span",
+            "start": 154,
+            "end": 154
+          }
+        }
+      ],
+      "content": "err02 = { $sel ->\n    [key] Value\n}\n",
+      "span": {
+        "type": "Span",
+        "start": 120,
+        "end": 156
+      }
+    }
+  ],
+  "span": {
+    "type": "Span",
+    "start": 0,
+    "end": 156
+  }
+}

fluent/src/resource.js

@@ -367,7 +367,15 @@ export default class FluentResource extends Map {
         variants[count++] = {key, value};
       }
 
-      return count > 0 ? {variants, star} : null;
+      if (count === 0) {
+        return null;
+      }
+
+      if (star === undefined) {
+        throw new FluentError("Expected default variant");
+      }
+
+      return {variants, star};
     }
 
     function parseVariantKey() {

fluent/test/fixtures_structure/select_expressions.json

@@ -0,0 +1 @@
+{}