Fix HEEx directive injections

queries/heex/injections.scm

@@ -1,14 +1,25 @@
-; HEEx directives can span multiple interpolated lines of Elixir
-(directive [
-  (expression_value) 
-  (partial_expression_value)
-] @injection.content
+; directives are standalone tags like '<%= @x %>'
+;
+; partial_expression_values are elixir code that is part of an expression that
+; spans multiple directive nodes, so they must be combined. For example:
+;     <%= if true do %>
+;       <p>hello, tree-sitter!</p>
+;     <% end %>
+(directive
+  (partial_expression_value) @injection.content
   (#set! injection.language "elixir")
-  (#set! injection.combined))  
+  (#set! injection.include-children)
+  (#set! injection.combined))
 
-; HEEx Elixir expressions are always within a tag or component
-(expression 
-  (expression_value) @injection.content 
+; Regular expression_values do not need to be combined
+((directive
+  (expression_value) @injection.content)
+  (#set! injection.language "elixir"))
+
+; expressions live within HTML tags, and do not need to be combined
+;     <link href={ Routes.static_path(..) } />
+(expression
+  (expression_value) @injection.content
   (#set! injection.language "elixir"))
 
 ; HEEx comments