4 files changed, 98 insertions, 21 deletions

diff --git a/Cargo.lock b/Cargo.lock
index a5a43cffc..e9383a89a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -904,6 +904,7 @@ dependencies = [
  "ra_syntax 0.1.0",
  "ra_text_edit 0.1.0",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_lexer 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "test_utils 0.1.0",
 ]
 
diff --git a/crates/ra_assists/Cargo.toml b/crates/ra_assists/Cargo.toml
index 02966bbda..d3b6aeb36 100644
--- a/crates/ra_assists/Cargo.toml
+++ b/crates/ra_assists/Cargo.toml
@@ -11,6 +11,7 @@ join_to_string = "0.1.3"
 itertools = "0.8.0"
 arrayvec = "0.4.10"
 rustc-hash = "1.0.1"
+rustc_lexer = "0.1.0"
 
 ra_syntax = { path = "../ra_syntax" }
 ra_text_edit = { path = "../ra_text_edit" }
diff --git a/crates/ra_assists/src/assists/raw_string.rs b/crates/ra_assists/src/assists/raw_string.rs
index 388ee7e97..2d2e31e51 100644
--- a/crates/ra_assists/src/assists/raw_string.rs
+++ b/crates/ra_assists/src/assists/raw_string.rs
@@ -2,6 +2,7 @@
 
 use hir::db::HirDatabase;
 use ra_syntax::{ast::AstNode, ast::Literal, TextRange, TextUnit};
+use rustc_lexer;
 
 use crate::{Assist, AssistCtx, AssistId};
 
@@ -10,13 +11,51 @@ pub(crate) fn make_raw_string(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
     if literal.token().kind() != ra_syntax::SyntaxKind::STRING {
         return None;
     }
+    let token = literal.token();
+    let text = token.text().as_str();
+    let usual_string_range = find_usual_string_range(text)?;
+    let start_of_inside = usual_string_range.start().to_usize() + 1;
+    let end_of_inside = usual_string_range.end().to_usize();
+    let inside_str = &text[start_of_inside..end_of_inside];
+    let mut unescaped = String::with_capacity(inside_str.len());
+    let mut error = Ok(());
+    rustc_lexer::unescape::unescape_str(
+        inside_str,
+        &mut |_, unescaped_char| match unescaped_char {
+            Ok(c) => unescaped.push(c),
+            Err(_) => error = Err(()),
+        },
+    );
+    if error.is_err() {
+        return None;
+    }
     ctx.add_action(AssistId("make_raw_string"), "make raw string", |edit| {
         edit.target(literal.syntax().text_range());
-        edit.insert(literal.syntax().text_range().start(), "r");
+        let max_hash_streak = count_hashes(&unescaped);
+        let mut hashes = String::with_capacity(max_hash_streak + 1);
+        for _ in 0..hashes.capacity() {
+            hashes.push('#');
+        }
+        edit.replace(
+            literal.syntax().text_range(),
+            format!("r{}\"{}\"{}", hashes, unescaped, hashes),
+        );
     });
     ctx.build()
 }
 
+fn count_hashes(s: &str) -> usize {
+    let mut max_hash_streak = 0usize;
+    for idx in s.match_indices("\"#").map(|(i, _)| i) {
+        let (_, sub) = s.split_at(idx + 1);
+        let nb_hash = sub.chars().take_while(|c| *c == '#').count();
+        if nb_hash > max_hash_streak {
+            max_hash_streak = nb_hash;
+        }
+    }
+    max_hash_streak
+}
+
 fn find_usual_string_range(s: &str) -> Option<TextRange> {
     Some(TextRange::from_to(
         TextUnit::from(s.find('"')? as u32),
@@ -94,10 +133,10 @@ mod test {
             make_raw_string,
             r#"
             fn f() {
-                let s = <|>"random string";
+                let s = <|>"random\nstring";
             }
             "#,
-            r#""random string""#,
+            r#""random\nstring""#,
         );
     }
 
@@ -107,44 +146,69 @@ mod test {
             make_raw_string,
             r#"
             fn f() {
-                let s = <|>"random string";
+                let s = <|>"random\nstring";
             }
             "#,
-            r#"
+            r##"
             fn f() {
-                let s = <|>r"random string";
+                let s = <|>r#"random
+string"#;
             }
-            "#,
+            "##,
         )
     }
 
     #[test]
-    fn make_raw_string_with_escaped_works() {
+    fn make_raw_string_hashes_inside_works() {
         check_assist(
             make_raw_string,
-            r#"
+            r###"
             fn f() {
-                let s = <|>"random\nstring";
+                let s = <|>"#random##\nstring";
             }
-            "#,
-            r#"
+            "###,
+            r####"
             fn f() {
-                let s = <|>r"random\nstring";
+                let s = <|>r#"#random##
+string"#;
             }
-            "#,
+            "####,
         )
     }
 
     #[test]
-    fn make_raw_string_not_works() {
-        check_assist_not_applicable(
+    fn make_raw_string_closing_hashes_inside_works() {
+        check_assist(
+            make_raw_string,
+            r###"
+            fn f() {
+                let s = <|>"#random\"##\nstring";
+            }
+            "###,
+            r####"
+            fn f() {
+                let s = <|>r###"#random"##
+string"###;
+            }
+            "####,
+        )
+    }
+
+    #[test]
+    fn make_raw_string_nothing_to_unescape_works() {
+        check_assist(
             make_raw_string,
             r#"
             fn f() {
-                let s = <|>r"random string";
+                let s = <|>"random string";
             }
             "#,
-        );
+            r##"
+            fn f() {
+                let s = <|>r#"random string"#;
+            }
+            "##,
+        )
     }
 
     #[test]
@@ -369,4 +433,14 @@ mod test {
             "#,
         );
     }
+
+    #[test]
+    fn count_hashes_test() {
+        assert_eq!(0, count_hashes("abc"));
+        assert_eq!(0, count_hashes("###"));
+        assert_eq!(1, count_hashes("\"#abc"));
+        assert_eq!(0, count_hashes("#abc"));
+        assert_eq!(2, count_hashes("#ab\"##c"));
+        assert_eq!(4, count_hashes("#ab\"##\"####c"));
+    }
 }
diff --git a/docs/user/features.md b/docs/user/features.md
index 757a02838..8b7a8d7fc 100644
--- a/docs/user/features.md
+++ b/docs/user/features.md
@@ -459,17 +459,18 @@ fn foo<T: u32, F: FnOnce(T) -> T>() {}
 fn foo<T, F>() where T: u32, F: FnOnce(T) -> T {}
 ```
 
-- Make raw string
+- Make raw string unescaped
 
 ```rust
 // before:
 fn f() {
-    let s = <|>"abcd";
+    let s = <|>"ab\ncd";
 }
 
 // after:
 fn f() {
-    let s = <|>r"abcd";
+    let s = <|>r#"ab
+cd"#;
 }
 ```