6 files changed, 104 insertions, 35 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 3a3793581..a63eac57a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -763,6 +763,7 @@ dependencies = [
  "languageserver-types 0.53.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proptest 0.8.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_analysis 0.1.0",
  "ra_editor 0.1.0",
  "ra_syntax 0.1.0",
diff --git a/crates/ra_lsp_server/Cargo.toml b/crates/ra_lsp_server/Cargo.toml
index 3c8c240cd..d73ff158f 100644
--- a/crates/ra_lsp_server/Cargo.toml
+++ b/crates/ra_lsp_server/Cargo.toml
@@ -34,6 +34,8 @@ ra_analysis = { path = "../ra_analysis" }
 gen_lsp_server = { path = "../gen_lsp_server" }
 ra_vfs = { path = "../ra_vfs" }
 
+proptest = "0.8.7"
+
 [dev-dependencies]
 tempdir = "0.3.7"
-test_utils = { path = "../test_utils" }
+test_utils = { path = "../test_utils" }
\ No newline at end of file
diff --git a/crates/ra_lsp_server/src/conv.rs b/crates/ra_lsp_server/src/conv.rs
index 051f1f995..1db499175 100644
--- a/crates/ra_lsp_server/src/conv.rs
+++ b/crates/ra_lsp_server/src/conv.rs
@@ -386,3 +386,64 @@ where
         self.iter.next().map(|item| item.conv_with(self.ctx))
     }
 }
+
+#[cfg(test)]
+mod test {
+    use proptest::{prelude::*, proptest, proptest_helper};
+    use super::*;
+    use ra_text_edit::test_utils::{arb_text, arb_offset, arb_edits};
+
+    #[derive(Debug)]
+    struct ArbTextWithOffsetAndEdits {
+        text: String,
+        offset: TextUnit,
+        edits: Vec<AtomTextEdit>,
+    }
+
+    fn arb_text_with_offset_and_edits() -> BoxedStrategy<ArbTextWithOffsetAndEdits> {
+        arb_text()
+            .prop_flat_map(|text| {
+                (arb_offset(&text), arb_edits(&text), Just(text)).prop_map(
+                    |(offset, edits, text)| ArbTextWithOffsetAndEdits {
+                        text,
+                        offset,
+                        edits,
+                    },
+                )
+            })
+            .boxed()
+    }
+
+    fn translate_offset_with_edit_naive(
+        pre_edit_text: String,
+        offset: TextUnit,
+        edits: &[AtomTextEdit],
+    ) -> LineCol {
+        // apply edits ordered from last to first
+        // since they should not overlap we can just use start()
+        let mut edits: Vec<AtomTextEdit> = edits.to_vec();
+        edits.sort_by_key(|x| -(x.delete.start().to_usize() as isize));
+
+        let mut text = pre_edit_text;
+
+        for edit in &edits {
+            let range = edit.delete.start().to_usize()..edit.delete.end().to_usize();
+            text.replace_range(range, &edit.insert);
+        }
+
+        let line_index = LineIndex::new(&text);
+
+        line_index.line_col(offset)
+    }
+
+    proptest! {
+        #[test]
+        fn test_translate_offset_with_edit(x in arb_text_with_offset_and_edits()) {
+            if x.edits.len() <= 1 {
+                let expected = translate_offset_with_edit_naive(x.text.clone(), x.offset, &x.edits);
+                let actual = translate_offset_with_edit(&LineIndex::new(&x.text), x.offset, &x.edits);
+                assert_eq!(actual, expected);
+            }
+        }
+    }
+}
diff --git a/crates/ra_text_edit/Cargo.toml b/crates/ra_text_edit/Cargo.toml
index 67dfd0924..e0db49688 100644
--- a/crates/ra_text_edit/Cargo.toml
+++ b/crates/ra_text_edit/Cargo.toml
@@ -7,7 +7,7 @@ publish = false
 
 [dependencies]
 text_unit = "0.1.5"
+proptest = "0.8.7"
 
 [dev-dependencies]
 test_utils = { path = "../test_utils" }
-proptest = "0.8.7"
diff --git a/crates/ra_text_edit/src/lib.rs b/crates/ra_text_edit/src/lib.rs
index 0a407795e..89600413a 100644
--- a/crates/ra_text_edit/src/lib.rs
+++ b/crates/ra_text_edit/src/lib.rs
@@ -1,6 +1,5 @@
 mod text_edit;
 pub mod text_utils;
-#[cfg(test)]
 pub mod test_utils;
 
 pub use crate::text_edit::{TextEdit, TextEditBuilder};
diff --git a/crates/ra_text_edit/src/test_utils.rs b/crates/ra_text_edit/src/test_utils.rs
index 29301bff3..4a0ebc08e 100644
--- a/crates/ra_text_edit/src/test_utils.rs
+++ b/crates/ra_text_edit/src/test_utils.rs
@@ -1,4 +1,4 @@
-use proptest::{prelude::*, proptest, proptest_helper};
+use proptest::prelude::*;
 use text_unit::{TextUnit, TextRange};
 use crate::AtomTextEdit;
 
@@ -66,42 +66,48 @@ pub fn arb_edits(text: &str) -> BoxedStrategy<Vec<AtomTextEdit>> {
         .boxed()
 }
 
-fn arb_text_with_edits() -> BoxedStrategy<(String, Vec<AtomTextEdit>)> {
-    let text = arb_text();
-    text.prop_flat_map(|s| {
-        let edits = arb_edits(&s);
-        (Just(s), edits)
-    })
-    .boxed()
-}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use proptest::{proptest, proptest_helper};
 
-fn intersect(r1: TextRange, r2: TextRange) -> Option<TextRange> {
-    let start = r1.start().max(r2.start());
-    let end = r1.end().min(r2.end());
-    if start <= end {
-        Some(TextRange::from_to(start, end))
-    } else {
-        None
+    fn arb_text_with_edits() -> BoxedStrategy<(String, Vec<AtomTextEdit>)> {
+        let text = arb_text();
+        text.prop_flat_map(|s| {
+            let edits = arb_edits(&s);
+            (Just(s), edits)
+        })
+        .boxed()
     }
-}
 
-proptest! {
-    #[test]
-    fn atom_text_edits_are_valid((text, edits) in arb_text_with_edits()) {
-        proptest_atom_text_edits_are_valid(text, edits)
+    fn intersect(r1: TextRange, r2: TextRange) -> Option<TextRange> {
+        let start = r1.start().max(r2.start());
+        let end = r1.end().min(r2.end());
+        if start <= end {
+            Some(TextRange::from_to(start, end))
+        } else {
+            None
+        }
     }
-}
-
-fn proptest_atom_text_edits_are_valid(text: String, edits: Vec<AtomTextEdit>) {
-    // slicing doesn't panic
-    for e in &edits {
-        let _ = &text[e.delete];
+    proptest! {
+        #[test]
+        fn atom_text_edits_are_valid((text, edits) in arb_text_with_edits()) {
+            proptest_atom_text_edits_are_valid(text, edits)
+        }
     }
-    // ranges do not overlap
-    for (i1, e1) in edits.iter().skip(1).enumerate() {
-        for e2 in &edits[0..i1] {
-            if intersect(e1.delete, e2.delete).is_some() {
-                assert!(false, "Overlapping ranges {} {}", e1.delete, e2.delete);
+
+    fn proptest_atom_text_edits_are_valid(text: String, edits: Vec<AtomTextEdit>) {
+        // slicing doesn't panic
+        for e in &edits {
+            let _ = &text[e.delete];
+        }
+        // ranges do not overlap
+        for i in 1..edits.len() {
+            let e1 = &edits[i];
+            for e2 in &edits[0..i] {
+                if intersect(e1.delete, e2.delete).is_some() {
+                    assert!(false, "Overlapping ranges {} {}", e1.delete, e2.delete);
+                }
             }
         }
     }