Minor, move code

crates/rust-analyzer/src/lsp_utils.rs

@@ -1,9 +1,11 @@
 //! Utilities for LSP-related boilerplate code.
-use std::error::Error;
+use std::{error::Error, ops::Range};
 
+use crate::from_proto;
 use crossbeam_channel::Sender;
 use lsp_server::{Message, Notification};
 use ra_db::Canceled;
+use ra_ide::LineIndex;
 use serde::{de::DeserializeOwned, Serialize};
 
 pub fn show_message(
@@ -42,3 +44,116 @@ where
 {
     Notification::new(N::METHOD.to_string(), params)
 }
+
+pub(crate) fn apply_document_changes(
+    old_text: &mut String,
+    content_changes: Vec<lsp_types::TextDocumentContentChangeEvent>,
+) {
+    let mut line_index = LineIndex::new(old_text);
+    // The changes we got must be applied sequentially, but can cross lines so we
+    // have to keep our line index updated.
+    // Some clients (e.g. Code) sort the ranges in reverse. As an optimization, we
+    // remember the last valid line in the index and only rebuild it if needed.
+    // The VFS will normalize the end of lines to `\n`.
+    enum IndexValid {
+        All,
+        UpToLineExclusive(u64),
+    }
+
+    impl IndexValid {
+        fn covers(&self, line: u64) -> bool {
+            match *self {
+                IndexValid::UpToLineExclusive(to) => to > line,
+                _ => true,
+            }
+        }
+    }
+
+    let mut index_valid = IndexValid::All;
+    for change in content_changes {
+        match change.range {
+            Some(range) => {
+                if !index_valid.covers(range.end.line) {
+                    line_index = LineIndex::new(&old_text);
+                }
+                index_valid = IndexValid::UpToLineExclusive(range.start.line);
+                let range = from_proto::text_range(&line_index, range);
+                old_text.replace_range(Range::<usize>::from(range), &change.text);
+            }
+            None => {
+                *old_text = change.text;
+                index_valid = IndexValid::UpToLineExclusive(0);
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use lsp_types::{Position, Range, TextDocumentContentChangeEvent};
+
+    use super::*;
+
+    #[test]
+    fn test_apply_document_changes() {
+        macro_rules! c {
+            [$($sl:expr, $sc:expr; $el:expr, $ec:expr => $text:expr),+] => {
+                vec![$(TextDocumentContentChangeEvent {
+                    range: Some(Range {
+                        start: Position { line: $sl, character: $sc },
+                        end: Position { line: $el, character: $ec },
+                    }),
+                    range_length: None,
+                    text: String::from($text),
+                }),+]
+            };
+        }
+
+        let mut text = String::new();
+        apply_document_changes(&mut text, vec![]);
+        assert_eq!(text, "");
+        apply_document_changes(
+            &mut text,
+            vec![TextDocumentContentChangeEvent {
+                range: None,
+                range_length: None,
+                text: String::from("the"),
+            }],
+        );
+        assert_eq!(text, "the");
+        apply_document_changes(&mut text, c![0, 3; 0, 3 => " quick"]);
+        assert_eq!(text, "the quick");
+        apply_document_changes(&mut text, c![0, 0; 0, 4 => "", 0, 5; 0, 5 => " foxes"]);
+        assert_eq!(text, "quick foxes");
+        apply_document_changes(&mut text, c![0, 11; 0, 11 => "\ndream"]);
+        assert_eq!(text, "quick foxes\ndream");
+        apply_document_changes(&mut text, c![1, 0; 1, 0 => "have "]);
+        assert_eq!(text, "quick foxes\nhave dream");
+        apply_document_changes(
+            &mut text,
+            c![0, 0; 0, 0 => "the ", 1, 4; 1, 4 => " quiet", 1, 16; 1, 16 => "s\n"],
+        );
+        assert_eq!(text, "the quick foxes\nhave quiet dreams\n");
+        apply_document_changes(&mut text, c![0, 15; 0, 15 => "\n", 2, 17; 2, 17 => "\n"]);
+        assert_eq!(text, "the quick foxes\n\nhave quiet dreams\n\n");
+        apply_document_changes(
+            &mut text,
+            c![1, 0; 1, 0 => "DREAM", 2, 0; 2, 0 => "they ", 3, 0; 3, 0 => "DON'T THEY?"],
+        );
+        assert_eq!(text, "the quick foxes\nDREAM\nthey have quiet dreams\nDON'T THEY?\n");
+        apply_document_changes(&mut text, c![0, 10; 1, 5 => "", 2, 0; 2, 12 => ""]);
+        assert_eq!(text, "the quick \nthey have quiet dreams\n");
+
+        text = String::from("❤️");
+        apply_document_changes(&mut text, c![0, 0; 0, 0 => "a"]);
+        assert_eq!(text, "a❤️");
+
+        text = String::from("a\nb");
+        apply_document_changes(&mut text, c![0, 1; 1, 0 => "\nțc", 0, 1; 1, 1 => "d"]);
+        assert_eq!(text, "adcb");
+
+        text = String::from("a\nb");
+        apply_document_changes(&mut text, c![0, 1; 1, 0 => "ț\nc", 0, 2; 0, 2 => "c"]);
+        assert_eq!(text, "ațc\ncb");
+    }
+}