Fix #5046: Adjacent JSX (#5049)

* Fix #5046: Adjacent JSX

* check CSX only when wrapped in parentheses

* Fix indentation

* Add test for unlikely, but valid, JSX syntax

lib/coffeescript/nodes.js

@@ -671,23 +671,29 @@
       // A Block node does not return its entire body, rather it
       // ensures that the final expression is returned.
       makeReturn(res) {
-        var csxCheckIndex, expr, j, len, ref1;
+        var expr, expressions, last, lastExp, len, penult, ref1;
         len = this.expressions.length;
+        ref1 = this.expressions, [lastExp] = slice1.call(ref1, -1);
+        lastExp = (lastExp != null ? lastExp.unwrap() : void 0) || false;
+        // 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 (lastExp && lastExp instanceof Parens && lastExp.body.expressions.length > 1) {
+          ({
+            body: {expressions}
+          } = lastExp);
+          [penult, last] = slice1.call(expressions, -2);
+          penult = penult.unwrap();
+          last = last.unwrap();
+          if (penult instanceof Call && penult.csx && last instanceof Call && last.csx) {
+            expressions[expressions.length - 1].error('Adjacent JSX elements must be wrapped in an enclosing tag');
+          }
+        }
         while (len--) {
           expr = this.expressions[len];
           this.expressions[len] = expr.makeReturn(res);
           if (expr instanceof Return && !expr.expression) {
             this.expressions.splice(len, 1);
           }
-          // 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 = j = ref1 = len; (ref1 <= 0 ? j <= 0 : j >= 0); csxCheckIndex = ref1 <= 0 ? ++j : --j) {
-              if (this.expressions[csxCheckIndex].unwrapAll().csx) {
-                expr.error('Adjacent JSX elements must be wrapped in an enclosing tag');
-              }
-            }
-          }
           break;
         }
         return this;

src/nodes.coffee

@@ -478,16 +478,21 @@ exports.Block = class Block extends Base
   # ensures that the final expression is returned.
   makeReturn: (res) ->
     len = @expressions.length
+    [..., lastExp] = @expressions
+    lastExp = lastExp?.unwrap() or no
+    # 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 lastExp and lastExp instanceof Parens and lastExp.body.expressions.length > 1
+      {body:{expressions}} = lastExp
+      [..., penult, last] = expressions
+      penult = penult.unwrap()
+      last = last.unwrap()
+      if penult instanceof Call and penult.csx and last instanceof Call and last.csx
+        expressions[expressions.length - 1].error 'Adjacent JSX elements must be wrapped in an enclosing tag'
     while len--
       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
 

test/csx.coffee

@@ -771,11 +771,11 @@ test 'JSX fragments: fragment with text nodes', ->
 
 test 'JSX fragments: fragment with component nodes', ->
   eqJS '''
-   Component = (props) =>
-     <Fragment>
-       <OtherComponent />
-       <OtherComponent />
-     </Fragment>
+    Component = (props) =>
+      <Fragment>
+        <OtherComponent />
+        <OtherComponent />
+      </Fragment>
   ''', '''
     var Component;
 
@@ -821,3 +821,20 @@ test '#5055: JSX expression indentation bug', ->
       {typeof a !== "undefined" && a !== null ? a : <span />}
     </div>;
   '''
+
+# JSX is like XML, in that there needs to be a root element; but
+# technically, adjacent top-level elements where only the last one
+# is returned (as opposed to a fragment or root element) is permissible
+# syntax. It’s almost certainly an error, but it’s valid, so need to leave it
+# to linters to catch. https://github.com/jashkenas/coffeescript/pull/5049
+test '“Adjacent” tags on separate lines should still compile', ->
+  eqJS '''
+    ->
+      <a />
+      <b />
+  ''', '''
+    (function() {
+      <a />;
+      return <b />;
+    });
+  '''

test/error_messages.coffee

@@ -1663,15 +1663,6 @@ 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>
@@ -1682,7 +1673,17 @@ test '#5034: CSX error: Adjacent JSX elements must be wrapped in an enclosing ta
       <Row>b</Row>
        ^^^^^^^^^^^
   '''
-
+  assertErrorFormat '''
+    render = -> (
+      a = "foo"
+      <Row>a</Row>
+      <Row>b</Row>
+    )
+  ''', '''
+    [stdin]:4:4: 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: ->