From 8ed06d766f5b3bf42916b30f52c97ca2478128bf Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Tue, 4 Sep 2018 12:48:39 +0300
Subject: better extend selection

---
 crates/libeditor/src/extend_selection.rs | 83 +++++++++++++++++++++++---------
 1 file changed, 59 insertions(+), 24 deletions(-)

diff --git a/crates/libeditor/src/extend_selection.rs b/crates/libeditor/src/extend_selection.rs
index 3adb1e45e..9dc59e254 100644
--- a/crates/libeditor/src/extend_selection.rs
+++ b/crates/libeditor/src/extend_selection.rs
@@ -1,7 +1,7 @@
 use libsyntax2::{
     File, TextRange, SyntaxNodeRef, TextUnit,
     SyntaxKind::*,
-    algo::{find_leaf_at_offset, find_covering_node, ancestors, Direction, siblings},
+    algo::{find_leaf_at_offset, LeafAtOffset, find_covering_node, ancestors, Direction, siblings},
 };
 
 pub fn extend_selection(file: &File, range: TextRange) -> Option<TextRange> {
@@ -13,30 +13,15 @@ pub(crate) fn extend(root: SyntaxNodeRef, range: TextRange) -> Option<TextRange>
     if range.is_empty() {
         let offset = range.start();
         let mut leaves = find_leaf_at_offset(root, offset);
-        if let Some(leaf) = leaves.clone().find(|node| node.kind() != WHITESPACE) {
-            return Some(leaf.range());
+        if leaves.clone().all(|it| it.kind() == WHITESPACE) {
+            return Some(extend_ws(root, leaves.next()?, offset));
         }
-        let ws = leaves.next()?;
-        let ws_text = ws.leaf_text().unwrap();
-        let suffix = TextRange::from_to(offset, ws.range().end()) - ws.range().start();
-        let prefix = TextRange::from_to(ws.range().start(), offset) - ws.range().start();
-        let ws_suffix = &ws_text.as_str()[suffix];
-        let ws_prefix = &ws_text.as_str()[prefix];
-        if ws_text.contains("\n") && !ws_suffix.contains("\n") {
-            if let Some(node) = ws.next_sibling() {
-                let start = match ws_prefix.rfind('\n') {
-                    Some(idx) => ws.range().start() + TextUnit::from((idx + 1) as u32),
-                    None => node.range().start()
-                };
-                let end = if root.text().char_at(node.range().end()) == Some('\n') {
-                    node.range().end() + TextUnit::of_char('\n')
-                } else {
-                    node.range().end()
-                };
-                return Some(TextRange::from_to(start, end));
-            }
-        }
-        return Some(ws.range());
+        let leaf = match leaves {
+            LeafAtOffset::None => return None,
+            LeafAtOffset::Single(l) => l,
+            LeafAtOffset::Between(l, r) => pick_best(l, r),
+        };
+        return Some(leaf.range());
     };
     let node = find_covering_node(root, range);
     if node.kind() == COMMENT && range == node.range() {
@@ -51,6 +36,40 @@ pub(crate) fn extend(root: SyntaxNodeRef, range: TextRange) -> Option<TextRange>
     }
 }
 
+fn extend_ws(root: SyntaxNodeRef, ws: SyntaxNodeRef, offset: TextUnit) -> TextRange {
+    let ws_text = ws.leaf_text().unwrap();
+    let suffix = TextRange::from_to(offset, ws.range().end()) - ws.range().start();
+    let prefix = TextRange::from_to(ws.range().start(), offset) - ws.range().start();
+    let ws_suffix = &ws_text.as_str()[suffix];
+    let ws_prefix = &ws_text.as_str()[prefix];
+    if ws_text.contains("\n") && !ws_suffix.contains("\n") {
+        if let Some(node) = ws.next_sibling() {
+            let start = match ws_prefix.rfind('\n') {
+                Some(idx) => ws.range().start() + TextUnit::from((idx + 1) as u32),
+                None => node.range().start()
+            };
+            let end = if root.text().char_at(node.range().end()) == Some('\n') {
+                node.range().end() + TextUnit::of_char('\n')
+            } else {
+                node.range().end()
+            };
+            return TextRange::from_to(start, end);
+        }
+    }
+    ws.range()
+}
+
+fn pick_best<'a>(l: SyntaxNodeRef<'a>, r: SyntaxNodeRef<'a>) -> SyntaxNodeRef<'a> {
+    return if priority(r) > priority(l) { r } else { l };
+    fn priority(n: SyntaxNodeRef) -> usize {
+        match n.kind() {
+            WHITESPACE => 0,
+            IDENT | SELF_KW | SUPER_KW | CRATE_KW => 2,
+            _ => 1,
+        }
+    }
+}
+
 fn extend_comments(node: SyntaxNodeRef) -> Option<TextRange> {
     let left = adj_comments(node, Direction::Backward);
     let right = adj_comments(node, Direction::Forward);
@@ -129,4 +148,20 @@ fn bar(){}
             &["// 1 + 1", "// fn foo() {\n// 1 + 1\n// }"]
         );
     }
+
+    #[test]
+    fn test_extend_selection_prefer_idents() {
+        do_check(
+            r#"
+fn main() { foo<|>+bar;}
+    "#,
+            &["foo", "foo+bar"]
+        );
+        do_check(
+            r#"
+fn main() { foo+<|>bar;}
+    "#,
+            &["bar", "foo+bar"]
+        );
+    }
 }
-- 
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