Fix wrong handling of nested templates with block

askama_derive/src/generator.rs

@@ -746,7 +746,7 @@ impl<'a> Generator<'a> {
             }
         };
 
-        mem::drop(mem::replace(&mut self.buf_writable.buf, current_buf));
+        self.buf_writable.buf = current_buf;
 
         let mut filter_buf = Buffer::new(buf.indent);
         let Filter {
@@ -904,16 +904,6 @@ impl<'a> Generator<'a> {
         name: Option<&'a str>,
         outer: Ws,
     ) -> Result<usize, CompileError> {
-        let block_fragment_write = self.input.block == name && self.buf_writable.discard;
-
-        // Allow writing to the buffer if we're in the block fragment
-        let mut prev_buf_discard = buf.discard;
-        if block_fragment_write {
-            self.buf_writable.discard = false;
-        } else if self.buf_writable.discard {
-            prev_buf_discard = mem::replace(&mut buf.discard, true);
-        }
-
         // Flush preceding whitespace according to the outer WS spec
         self.flush_ws(outer);
 
@@ -932,6 +922,15 @@ impl<'a> Generator<'a> {
             (None, None) => return Err("cannot call 'super()' outside block".into()),
         };
 
+        self.write_buf_writable(buf)?;
+
+        let block_fragment_write = self.input.block == name && self.buf_writable.discard;
+        // Allow writing to the buffer if we're in the block fragment
+        if block_fragment_write {
+            self.buf_writable.discard = false;
+        }
+        let prev_buf_discard = mem::replace(&mut buf.discard, self.buf_writable.discard);
+
         // Get the block definition from the heritage chain
         let heritage = self
             .heritage
@@ -976,6 +975,7 @@ impl<'a> Generator<'a> {
             // Need to flush the buffer before popping the variable stack
             child.write_buf_writable(buf)?;
         }
+
         child.flush_ws(def.ws2);
         self.buf_writable = child.buf_writable;
 

testing/templates/blocks.txt

@@ -0,0 +1,11 @@
+{% block index %}
+Section: {{ s1 }}
+{% endblock %}
+
+{% block section -%}
+  [
+  {%- for value in  values -%}
+    {{ value }}
+  {%- endfor -%}
+  ]
+{%- endblock %}

testing/tests/block_fragments.rs

@@ -11,7 +11,7 @@ struct FragmentSimple<'a> {
 fn test_fragment_simple() {
     let simple = FragmentSimple { name: "world" };
 
-    assert_eq!(simple.render().unwrap(), "\n\n<p>Hello world!</p>\n");
+    assert_eq!(simple.render().unwrap(), "\n<p>Hello world!</p>\n");
 }
 
 #[derive(Template)]
@@ -28,7 +28,7 @@ fn test_fragment_super() {
 
     assert_eq!(
         sup.render().unwrap(),
-        "\n\n<p>Hello world!</p>\n\n<p>Parent body content</p>\n\n"
+        "\n<p>Hello world!</p>\n\n<p>Parent body content</p>\n\n"
     );
 }
 
@@ -43,7 +43,7 @@ fn test_fragment_nested_block() {
 
     assert_eq!(
         nested_block.render().unwrap(),
-        "\n\n<p>I should be here.</p>\n"
+        "\n<p>I should be here.</p>\n"
     );
 }
 
@@ -61,7 +61,7 @@ fn test_fragment_nested_super() {
 
     assert_eq!(
         nested_sup.render().unwrap(),
-        "\n\n<p>Hello world!</p>\n\n[\n<p>Parent body content</p>\n]\n\n"
+        "\n<p>Hello world!</p>\n\n[\n<p>Parent body content</p>\n]\n\n"
     );
 }
 
@@ -79,5 +79,27 @@ fn test_fragment_unused_expression() {
         required: "Required",
     };
 
-    assert_eq!(unused_expr.render().unwrap(), "\n\n<p>Required</p>\n");
+    assert_eq!(unused_expr.render().unwrap(), "\n<p>Required</p>\n");
+}
+
+#[derive(Template)]
+#[template(path = "blocks.txt", block = "index")]
+struct RenderInPlace<'a> {
+    s1: Section<'a>,
+}
+
+#[derive(Template)]
+#[template(path = "blocks.txt", block = "section")]
+struct Section<'a> {
+    values: &'a [&'a str],
+}
+
+#[test]
+fn test_specific_block() {
+    let s1 = Section {
+        values: &["a", "b", "c"],
+    };
+    assert_eq!(s1.render().unwrap(), "[abc]");
+    let t = RenderInPlace { s1 };
+    assert_eq!(t.render().unwrap(), "\nSection: [abc]\n");
 }