indent: refactor logic to be more correct.

Thanks to atom-sane-indentation, nvim-treesitter and tree-sitter-indent.el
for inspiration.

2 files changed, 189 insertions, 48 deletions

diff --git a/helix-core/src/indent.rs b/helix-core/src/indent.rs
index 6b9a1ab1..7fbe7f82 100644
--- a/helix-core/src/indent.rs
+++ b/helix-core/src/indent.rs
@@ -27,7 +27,8 @@ fn indent_level_for_line(line: RopeSlice) -> usize {
 fn get_highest_syntax_node_at_bytepos(syntax: &Syntax, pos: usize) -> Option<Node> {
     let tree = syntax.root_layer.tree.as_ref().unwrap();
 
-    let mut node = match tree.root_node().named_descendant_for_byte_range(pos, pos) {
+    // named_descendant
+    let mut node = match tree.root_node().descendant_for_byte_range(pos, pos) {
         Some(node) => node,
         None => return None,
     };
@@ -43,91 +44,149 @@ fn get_highest_syntax_node_at_bytepos(syntax: &Syntax, pos: usize) -> Option<Nod
     Some(node)
 }
 
-fn walk(node: Option<Node>) -> usize {
-    let node = match node {
-        Some(node) => node,
-        None => return 0,
-    };
-
-    let parent = match node.parent() {
-        Some(node) => node,
-        None => return 0,
-    };
-
+fn walk(node: Option<Node>, newline: bool) -> usize {
     let mut increment = 0;
 
     // Hardcoded for rust for now
     let indent_scopes = &[
-        "block",
-        "function_item",
-        "closure_expression",
+        // indent except first or block?
         "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 = &[];
+    // this is for multiline things, such as:
+    // self.method()
+    //  .chain()
+    //  .chain()
+    //  where the first line isn't indented
+    let indent_except_first_scopes = &[
+        "block",
+        "arguments",
+        "declaration_list",
+        "field_declaration_list",
+        "enum_variant_list",
+        // "function_item",
+        // "call_expression",
+        // "closure_expression",
+        "binary_expression",
+        "field_expression",
+        //
+        "where_predicate", // where_clause instead?
+    ];
 
-    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 outdent = &["}", "]", ")"];
 
-    let parent_kind = parent.kind();
-    let is_scope = indent_scopes.iter().any(|scope| scope == &parent_kind);
+    let mut node = match node {
+        Some(node) => node,
+        None => return 0,
+    };
 
-    // && not_first_or_last_sibling
-    if is_scope {
-        increment += 1
+    // if we're calculating indentation for a brand new line then the current node will become the
+    // parent node. We need to take it's indentation level into account too.
+    let node_kind = node.kind();
+    if newline
+        && (indent_scopes.contains(&node_kind) || indent_except_first_scopes.contains(&node_kind))
+    {
+        increment += 1;
     }
 
-    // if last_scope && increment > 0 && ...{ ignore }
+    while let Some(parent) = node.parent() {
+        let not_first_sibling = node.prev_sibling().is_some();
+        let not_last_sibling = node.next_sibling().is_some();
+        let not_first_or_last_sibling = not_first_sibling && not_last_sibling;
+
+        let parent_kind = parent.kind();
+
+        // println!(
+        //     "name: {}\tparent: {}\trange:\t{} {}\tfirst={:?}\tlast={:?}",
+        //     node.kind(),
+        //     parent.kind(),
+        //     node.range().start_point,
+        //     node.range().end_point,
+        //     node.prev_sibling().is_none(),
+        //     node.next_sibling().is_none(),
+        // );
+
+        if outdent.contains(&node.kind()) {
+            // we outdent by skipping the rules for the current level and jumping up
+            node = parent;
+            continue;
+        }
+
+        let is_scope = indent_scopes.contains(&parent_kind);
+
+        // && not_first_or_last_sibling
+        if is_scope && not_first_or_last_sibling {
+            // println!("is_scope {}", parent_kind);
+            increment += 1
+        }
+
+        let is_scope = indent_except_first_scopes.contains(&parent_kind);
+
+        // && not_first_sibling
+        if is_scope && not_first_sibling {
+            // println!("is_scope_except_first {}", parent_kind);
+            increment += 1
+        }
+
+        // if last_scope && increment > 0 && ...{ ignore }
+
+        node = parent;
+    }
 
-    walk(Some(parent)) + increment
+    increment
 }
 
-fn find_first_non_whitespace_char(state: &State, line_num: usize) -> usize {
+fn find_first_non_whitespace_char(state: &State, line_num: usize) -> Option<usize> {
     let line = state.doc.line(line_num);
     let mut start = state.doc.line_to_char(line_num);
 
     // find first non-whitespace char
     for ch in line.chars() {
         // TODO: could use memchr with chunks?
-        if ch != ' ' && ch != '\t' {
-            break;
+        if ch != ' ' && ch != '\t' && ch != '\n' {
+            return Some(start);
         }
         start += 1;
     }
-    start
+
+    None
 }
 
 fn suggested_indent_for_line(syntax: Option<&Syntax>, state: &State, line_num: usize) -> usize {
     let line = state.doc.line(line_num);
     let current = indent_level_for_line(line);
 
-    let start = find_first_non_whitespace_char(state, line_num);
+    if let Some(start) = find_first_non_whitespace_char(state, line_num) {
+        return suggested_indent_for_pos(syntax, state, start, false);
+    };
 
-    suggested_indent_for_pos(syntax, state, start)
+    // if the line is blank, indent should be zero
+    0
 }
 
-pub fn suggested_indent_for_pos(syntax: Option<&Syntax>, state: &State, pos: usize) -> usize {
+// TODO: two usecases: if we are triggering this for a new, blank line:
+// - it should return 0 when mass indenting stuff
+// - it should look up the wrapper node and count it too when we press o/O
+pub fn suggested_indent_for_pos(
+    syntax: Option<&Syntax>,
+    state: &State,
+    pos: usize,
+    new_line: bool,
+) -> usize {
     if let Some(syntax) = syntax {
         let byte_start = state.doc.char_to_byte(pos);
         let node = get_highest_syntax_node_at_bytepos(syntax, byte_start);
 
-        let indentation = walk(node);
+        let indentation = walk(node, new_line);
         // special case for comments
 
+        // println!("------------");
         // if preserve_leading_whitespace
 
         indentation
@@ -155,11 +214,52 @@ mod test {
     #[test]
     fn test_suggested_indent_for_line() {
         let doc = Rope::from(
-            "mod test {
+            "
+mod test {
     fn hello_world() {
-        1 + 1
+        1 + 1;
+
+        let does_indentation_work = 1;
+
+        let test_function = function_with_param(this_param,
+            that_param
+        );
+
+        let test_function = function_with_param(
+            this_param,
+            that_param
+        );
+
+        let test_function = function_with_proper_indent(param1,
+            param2,
+        );
+
+        let selection = Selection::new(
+            changes
+                .clone()
+                .map(|(start, end, text): (usize, usize, Option<Tendril>)| {
+                    let len = text.map(|text| text.len()).unwrap() - 1; // minus newline
+                    let pos = start + len;
+                    Range::new(pos, pos)
+                })
+                .collect(),
+            0,
+        );
+
+        return;
     }
 }
+
+impl<A, D> MyTrait<A, D> for YourType
+where
+    A: TraitB + TraitC,
+    D: TraitE + TraitF,
+{
+
+}
+#[test]
+//
+
 ",
         );
 
@@ -171,10 +271,49 @@ mod test {
         let highlight_config = language_config.highlight_config(&[]).unwrap().unwrap();
         let syntax = Syntax::new(&state.doc, highlight_config.clone());
 
-        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 0), 0); // mod
-        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 1), 1); // fn
-        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 2), 2); // 1 + 1
-        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 4), 1); // }
-        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 5), 0); // }
+        // {
+        //   {
+        //     1 + 1
+        //   }
+        // }
+        // assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 1), 0); // {
+        // assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 2), 1); // {
+        // assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 3), 2); //
+        // assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 4), 1); // }
+        // assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 5), 0); // }
+
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 1), 0); // mod
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 2), 1); // fn
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 3), 2); // 1 + 1
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 4), 0); //
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 5), 2); // does_indentation_work
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 7), 2); // let test_function
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 8), 3); // that_param
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 9), 2); // );
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 10), 0); //
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 11), 2); // let test_function
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 12), 3); // this_param
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 13), 3); // that_param
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 14), 2); // );
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 15), 0); //
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 16), 2); // let test_function
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 17), 3); // param2
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 18), 2); // );
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 20), 2); // let selection
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 21), 3); // changes
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 22), 4); // clone()
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 23), 4); // map()
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 24), 5); // let len
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 25), 5); // let pos
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 26), 5); // Range
+
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 27), 4); // })
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 28), 4); // .collect(),
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 29), 3); // 0,
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 30), 2); // })
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 31), 0); //
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 32), 2); // return;
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 33), 1); // }
+        assert_eq!(suggested_indent_for_line(Some(&syntax), &state, 34), 0); // }
     }
 }
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 8216437d..a11c3145 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -535,6 +535,7 @@ pub fn open_below(cx: &mut Context) {
             cx.view.doc.syntax.as_ref(),
             &cx.view.doc.state,
             index,
+            true,
         );
         let indent = " ".repeat(TAB_WIDTH).repeat(indent_level);
         let mut text = String::with_capacity(1 + indent.len());
@@ -654,6 +655,7 @@ pub mod insert {
                 cx.view.doc.syntax.as_ref(),
                 &cx.view.doc.state,
                 range.head,
+                true,
             );
             let indent = " ".repeat(TAB_WIDTH).repeat(indent_level);
             let mut text = String::with_capacity(1 + indent.len());