Make tree-sitter the default parser

CHANGELOG.md

@@ -6,6 +6,9 @@ Fixed a crash on removing whole files.
 
 ### Parsing
 
+Tree-sitter parsing is now the default, unless the environment
+variable DFT_RX is set.
+
 Tree-sitter parser: Improved handling of string literals. Improved
 matching of delimiters.
 

README.md

@@ -11,16 +11,12 @@ It currently supports the following languages:
 * CSS
 * Emacs Lisp
 * Go
-* JavaScript
+* JavaScript (including JSX)
 * JSON
 * OCaml
 * Rust
 * Scheme
 
-The parsing logic is based on matched delimiters, so difftastic tends
-to give best results on heavily parenthesised code (e.g. Lisps or
-JSON).
-
 If a file has an unrecognised extension, difftastic uses a
 line-oriented diff.
 
@@ -28,20 +24,14 @@ line-oriented diff.
 
 (1) Parsing.
 
-Difftastic treats source code as a sequence of atoms or (possibly
-nested) lists.
-
-Language syntax is defined in `src/regex_parser.rs`: you provide regular
-expressions for atoms (including comments), open delimiters, and close
-delimiters.
-
-This is heavily inspired by
-[Comby](https://github.com/comby-tools/comby), which handles a large
-number of languages by using a similar approach.
+Difftastic uses
+[tree-sitter](https://tree-sitter.github.io/tree-sitter/) for
+parsing. The concrete syntax tree is then converted to a sequence of
+atoms or (possibly nested) lists.
 
-(A [tree-sitter](https://tree-sitter.github.io/tree-sitter/) parsing
-backend is also available by setting `DFT_TS=y`. It is not yet
-recommended.)
+The command line flags `--dump-ts` and `--dump-syntax` will display
+the syntax trees for a given file. Difftastic also has a simple regex-based
+parser which can be enabled with `DFT_RX=1`.
 
 (2) Diffing.
 

src/main.rs

@@ -198,10 +198,12 @@ fn main() {
 
     let extension = Path::new(&display_path).extension();
     let extension = extension.unwrap_or_else(|| OsStr::new(""));
-    let ts_lang = if env::var("DFT_TS").is_ok() {
-        tsp::from_extension(extension)
-    } else {
+    // Try tree-sitter parser first unless DFT_RX (difftastic regex)
+    // environment variable is set.
+    let ts_lang = if env::var("DFT_RX").is_ok() {
         None
+    } else {
+        tsp::from_extension(extension)
     };
 
     let (lang_name, lhs, rhs) = match ts_lang {