Compile `elif` tag to `elif` instead of `else: if`2.9-maintenance

This avoids deep nesting in case of many `{% elif .. %}` blocks (which
would fail during execution) and also deep recursion (which may fail
during compilation)

fixes #759

1 files changed, 7 insertions, 0 deletions

diff --git a/jinja2/compiler.py b/jinja2/compiler.py
index b2ab6fe..30826f3 100644
--- a/jinja2/compiler.py
+++ b/jinja2/compiler.py
@@ -1129,6 +1129,13 @@ class CodeGenerator(NodeVisitor):
         self.indent()
         self.blockvisit(node.body, if_frame)
         self.outdent()
+        for elif_ in node.elif_:
+            self.writeline('elif ', elif_)
+            self.visit(elif_.test, if_frame)
+            self.write(':')
+            self.indent()
+            self.blockvisit(elif_.body, if_frame)
+            self.outdent()
         if node.else_:
             self.writeline('else:')
             self.indent()