Flatten nullable types in Kotlin

Workaround for #589 and #411

CHANGELOG.md

@@ -4,7 +4,8 @@
 
 Added support for SCSS.
 
-Updated the Kotlin parser.
+Updated the Kotlin parser and improved handling of Kotlin nullable
+types.
 
 ### Command Line Interface
 

sample_files/compare.expected

@@ -1,5 +1,5 @@
 sample_files/Session_before.kt sample_files/Session_after.kt
-7b0c38d1fcc9b4e20c5fcf0070cb1620  -
+80c53658ee849d38f397863803677a02  -
 
 sample_files/ada_before.adb sample_files/ada_after.adb
 626e22f4f256ae591ece3f280176b3f7  -
@@ -151,6 +151,9 @@ sample_files/newick_before.nwk sample_files/newick_after.nwk
 sample_files/nix_before.nix sample_files/nix_after.nix
 e00b95a4cf3fa3edf994155d8656063f  -
 
+sample_files/nullable_before.kt sample_files/nullable_after.kt
+66da628a2c20e18059b8669aaa14a163  -
+
 sample_files/ocaml_before.ml sample_files/ocaml_after.ml
 2113c6c7959b8099f678d13953f7f44a  -
 

sample_files/nullable_after.kt

@@ -0,0 +1,3 @@
+class Foo {
+    val str: String
+}

sample_files/nullable_before.kt

@@ -0,0 +1,3 @@
+class Foo {
+    val str: String?
+}

src/parse/tree_sitter_parser.rs

@@ -615,7 +615,11 @@ pub fn from_language(language: guess::Language) -> TreeSitterConfig {
             let language = unsafe { tree_sitter_kotlin() };
             TreeSitterConfig {
                 language,
-                atom_nodes: vec!["line_string_literal", "character_literal"]
+                // Flattening nullable type means we can't diff the
+                // structure of complex types within, but it beats
+                // ignoring nullable changes.
+                // https://github.com/Wilfred/difftastic/issues/411
+                atom_nodes: vec!["line_string_literal", "character_literal", "nullable_type"]
                     .into_iter()
                     .collect(),
                 delimiter_tokens: vec![("(", ")"), ("{", "}"), ("[", "]"), ("<", ">")]