Fix jashkenas#5034: Adjacent JSX elements must be wrapped in an enclosing tag (jashkenas#5046)

Author: GeoffreyBooth

lib/coffeescript/nodes.js

@@ -482,6 +482,12 @@ exports.Block = class Block extends Base
       expr = @expressions[len]
       @expressions[len] = expr.makeReturn res
       @expressions.splice(len, 1) if expr instanceof Return and not expr.expression
+      # We also need to check that we’re not returning a CSX tag if there’s an
+      # adjacent one at the same level; JSX doesn’t allow that.
+      if expr.unwrapAll().csx
+        for csxCheckIndex in [len..0]
+          if @expressions[csxCheckIndex].unwrapAll().csx
+            expr.error 'Adjacent JSX elements must be wrapped in an enclosing tag'
       break
     this
 

src/nodes.coffee

@@ -1662,6 +1662,27 @@ test 'CSX error: invalid attributes', ->
          ^^^^^^^^^^^^^^^^
   '''
 
+test '#5034: CSX error: Adjacent JSX elements must be wrapped in an enclosing tag', ->
+  assertErrorFormat '''
+    render = ->
+      <Row>a</Row>
+      <Row>b</Row>
+  ''', '''
+    [stdin]:3:4: error: Adjacent JSX elements must be wrapped in an enclosing tag
+      <Row>b</Row>
+       ^^^^^^^^^^^
+  '''
+  assertErrorFormat '''
+    render = -> (
+      <Row>a</Row>
+      <Row>b</Row>
+    )
+  ''', '''
+    [stdin]:3:4: error: Adjacent JSX elements must be wrapped in an enclosing tag
+      <Row>b</Row>
+       ^^^^^^^^^^^
+  '''
+
 test 'Bound method called as callback before binding throws runtime error', ->
   class Base
     constructor: ->
@@ -1840,4 +1861,4 @@ test "#3933: prevent implicit calls when cotrol flow is missing `THEN`", ->
     [stdin]:2:10: error: unexpected ->
       when a ->
              ^^
-  '''
+  '''