fix: corrected partial_block_depth mechanism

Fixes #487

We can only increase `patial_block_depth` for scenarios where
consecutive `@partial-block` are rendered.

Author: sunng87

src/partial.rs

@@ -52,17 +52,24 @@ pub fn expand_partial<'reg: 'rc, 'rc>(
         return Err(RenderError::new("Cannot include self in >"));
     }
 
-    // if tname == PARTIAL_BLOCK
     let partial = find_partial(rc, r, d, tname)?;
 
     if let Some(t) = partial {
         // clone to avoid lifetime issue
         // FIXME refactor this to avoid
         let mut local_rc = rc.clone();
+
+        // if tname == PARTIAL_BLOCK
         let is_partial_block = tname == PARTIAL_BLOCK;
 
+        // add partial block depth there are consecutive partial
+        // blocks in the stack.
         if is_partial_block {
             local_rc.inc_partial_block_depth();
+        } else {
+            // depth cannot be lower than 0, which is guaranted in the
+            // `dec_partial_block_depth` method
+            local_rc.dec_partial_block_depth();
         }
 
         let mut block_created = false;
@@ -103,10 +110,6 @@ pub fn expand_partial<'reg: 'rc, 'rc>(
             local_rc.pop_block();
         }
 
-        if is_partial_block {
-            local_rc.dec_partial_block_depth();
-        }
-
         if d.template().is_some() {
             local_rc.pop_partial_block();
         }
@@ -297,7 +300,7 @@ mod test {
     }
 
     #[test]
-    fn test_nested_partials() {
+    fn test_nested_partial_block() {
         let mut handlebars = Registry::new();
         let template1 = "<outer>{{> @partial-block }}</outer>";
         let template2 = "{{#> t1 }}<inner>{{> @partial-block }}</inner>{{/ t1 }}";
@@ -453,7 +456,7 @@ name: there
     }
 
     #[test]
-    fn test_nested_partial() {
+    fn test_nested_partials() {
         let mut hb = Registry::new();
         hb.register_template_string("partial", "{{> @partial-block}}")
             .unwrap();
@@ -469,7 +472,8 @@ name: there
         .unwrap();
         assert_eq!(
             r#"    Yo
-    Yo 2"#,
+    Yo 2
+"#,
             hb.render("index", &()).unwrap()
         );
     }

src/render.rs

@@ -190,7 +190,10 @@ impl<'reg: 'rc, 'rc> RenderContext<'reg, 'rc> {
     }
 
     pub(crate) fn dec_partial_block_depth(&mut self) {
-        self.inner_mut().partial_block_depth -= 1;
+        let depth = &mut self.inner_mut().partial_block_depth;
+        if *depth > 0 {
+            *depth -= 1;
+        }
     }
 
     /// Remove a registered partial
@@ -275,6 +278,7 @@ impl<'reg, 'rc> fmt::Debug for RenderContextInner<'reg, 'rc> {
         f.debug_struct("RenderContextInner")
             .field("partials", &self.partials)
             .field("partial_block_stack", &self.partial_block_stack)
+            .field("partial_block_depth", &self.partial_block_depth)
             .field("root_template", &self.root_template)
             .field("current_template", &self.current_template)
             .field("disable_escape", &self.disable_escape)