Auto-indent on enter based on tree-sitter scopes.

1 files changed, 70 insertions, 12 deletions

diff --git a/helix-core/src/indent.rs b/helix-core/src/indent.rs
index 932eaa24..c834d8e2 100644
--- a/helix-core/src/indent.rs
+++ b/helix-core/src/indent.rs
@@ -4,6 +4,9 @@ use crate::{
     Rope, RopeSlice, State,
 };
 
+/// To determine indentation of a newly inserted line, figure out the indentation at the last col
+/// of the previous line.
+
 pub const TAB_WIDTH: usize = 4;
 
 fn indent_level_for_line(line: RopeSlice) -> usize {
@@ -53,22 +56,51 @@ fn walk(node: Option<Node>) -> usize {
 
     let mut increment = 0;
 
-    let not_first_or_last_sibling = node.next_sibling().is_some() && node.prev_sibling().is_some();
-    let is_scope = true;
-
-    if not_first_or_last_sibling && is_scope {
-        increment += 1;
+    // Hardcoded for rust for now
+    let indent_scopes = &[
+        "block",
+        "function_item",
+        "closure_expression",
+        "while_expression",
+        "for_expression",
+        "loop_expression",
+        "if_expression",
+        "if_let_expression",
+        "binary_expression",
+        "match_expression",
+        "match_arm",
+        //
+        "struct_item",
+        "enum_item",
+        "impl_item",
+        //
+        "mod_item",
+    ];
+
+    // let indent_except_first_scopes = &[];
+
+    let not_first_sibling = node.next_sibling().is_some();
+    let not_last_sibling = node.prev_sibling().is_some();
+    let not_first_or_last_sibling = not_first_sibling && not_last_sibling;
+
+    let parent_kind = parent.kind();
+    let is_scope = indent_scopes.iter().any(|scope| scope == &parent_kind);
+
+    // && not_first_or_last_sibling
+    if is_scope {
+        increment += 1
     }
 
+    // if last_scope && increment > 0 && ...{ ignore }
+
     walk(Some(parent)) + increment
 }
 
-// for_line_at_col
 fn suggested_indent_for_line(state: &State, line_num: usize) -> usize {
     let line = state.doc.line(line_num);
     let current = indent_level_for_line(line);
 
-    let mut byte_start = state.doc.line_to_byte(line_num);
+    let mut start = state.doc.line_to_char(line_num);
 
     // find first non-whitespace char
     for ch in line.chars() {
@@ -76,18 +108,23 @@ fn suggested_indent_for_line(state: &State, line_num: usize) -> usize {
         if ch != ' ' && ch != '\t' {
             break;
         }
-        byte_start += 1;
+        start += 1;
     }
 
+    suggested_indent_for_pos(state, start)
+}
+
+pub fn suggested_indent_for_pos(state: &State, pos: usize) -> usize {
     if let Some(syntax) = &state.syntax {
-        let node = get_highest_syntax_node_at_bytepos(state.syntax.as_ref().unwrap(), byte_start);
+        let byte_start = state.doc.char_to_byte(pos);
+        let node = get_highest_syntax_node_at_bytepos(syntax, byte_start);
 
-        // let indentation = walk()
+        let indentation = walk(node);
         // special case for comments
 
         // if preserve_leading_whitespace
 
-        unimplemented!()
+        indentation
     } else {
         // TODO: case for non-tree sitter grammars
         0
@@ -99,7 +136,7 @@ mod test {
     use super::*;
 
     #[test]
-    fn indent_level() {
+    fn test_indent_level() {
         let line = Rope::from("        fn new"); // 8 spaces
         assert_eq!(indent_level_for_line(line.slice(..)), 2);
         let line = Rope::from("\t\t\tfn new"); // 3 tabs
@@ -108,4 +145,25 @@ mod test {
         let line = Rope::from("\t    \tfn new"); // 1 tab, 4 spaces, tab
         assert_eq!(indent_level_for_line(line.slice(..)), 3);
     }
+
+    #[test]
+    fn test_suggested_indent_for_line() {
+        let doc = Rope::from(
+            "mod test {
+    fn hello_world() {
+        1 + 1
+    }
+}
+",
+        );
+
+        let mut state = State::new(doc);
+        state.set_language("source.rust", &[]);
+
+        assert_eq!(suggested_indent_for_line(&state, 0), 0); // mod
+        assert_eq!(suggested_indent_for_line(&state, 1), 1); // fn
+        assert_eq!(suggested_indent_for_line(&state, 2), 2); // 1 + 1
+        assert_eq!(suggested_indent_for_line(&state, 4), 1); // }
+        assert_eq!(suggested_indent_for_line(&state, 5), 0); // }
+    }
 }