Fix handling of whitespace when applying SSR within macro expansions.

I originally did replacement by passing in the full file text. Then as some point I thought I could do without it. Turns out calling .text() on a node coming from a macro expansion isn't a great idea, especially when you then try and use ranges from the original source to cut that text. The test I added here actually panics without the rest of this change (sorry I didn't notice sooner).

crates/ra_ssr/src/lib.rs

@@ -69,7 +69,8 @@ impl<'db> MatchFinder<'db> {
         if matches.matches.is_empty() {
             None
         } else {
-            Some(replacing::matches_to_edit(&matches))
+            use ra_db::SourceDatabaseExt;
+            Some(replacing::matches_to_edit(&matches, &self.sema.db.file_text(file_id)))
         }
     }
 

crates/ra_ssr/src/matching.rs

@@ -585,7 +585,7 @@ mod tests {
             "1+2"
         );
 
-        let edit = crate::replacing::matches_to_edit(&matches);
+        let edit = crate::replacing::matches_to_edit(&matches, input);
         let mut after = input.to_string();
         edit.apply(&mut after);
         assert_eq!(after, "fn main() { bar(1+2); }");

crates/ra_ssr/src/replacing.rs

@@ -10,21 +10,25 @@ use ra_text_edit::TextEdit;
 /// Returns a text edit that will replace each match in `matches` with its corresponding replacement
 /// template. Placeholders in the template will have been substituted with whatever they matched to
 /// in the original code.
-pub(crate) fn matches_to_edit(matches: &SsrMatches) -> TextEdit {
-    matches_to_edit_at_offset(matches, 0.into())
+pub(crate) fn matches_to_edit(matches: &SsrMatches, file_src: &str) -> TextEdit {
+    matches_to_edit_at_offset(matches, file_src, 0.into())
 }
 
-fn matches_to_edit_at_offset(matches: &SsrMatches, relative_start: TextSize) -> TextEdit {
+fn matches_to_edit_at_offset(
+    matches: &SsrMatches,
+    file_src: &str,
+    relative_start: TextSize,
+) -> TextEdit {
     let mut edit_builder = ra_text_edit::TextEditBuilder::default();
     for m in &matches.matches {
-        edit_builder.replace(m.range.checked_sub(relative_start).unwrap(), render_replace(m));
+        edit_builder
+            .replace(m.range.checked_sub(relative_start).unwrap(), render_replace(m, file_src));
     }
     edit_builder.finish()
 }
 
-fn render_replace(match_info: &Match) -> String {
+fn render_replace(match_info: &Match, file_src: &str) -> String {
     let mut out = String::new();
-    let match_start = match_info.matched_node.text_range().start();
     for r in &match_info.template.tokens {
         match r {
             PatternElement::Token(t) => out.push_str(t.text.as_str()),
@@ -33,16 +37,13 @@ fn render_replace(match_info: &Match) -> String {
                     match_info.placeholder_values.get(&Var(p.ident.to_string()))
                 {
                     let range = &placeholder_value.range.range;
-                    let mut matched_text = if let Some(node) = &placeholder_value.node {
-                        node.text().to_string()
-                    } else {
-                        let relative_range = range.checked_sub(match_start).unwrap();
-                        match_info.matched_node.text().to_string()
-                            [usize::from(relative_range.start())..usize::from(relative_range.end())]
-                            .to_string()
-                    };
-                    let edit =
-                        matches_to_edit_at_offset(&placeholder_value.inner_matches, range.start());
+                    let mut matched_text =
+                        file_src[usize::from(range.start())..usize::from(range.end())].to_owned();
+                    let edit = matches_to_edit_at_offset(
+                        &placeholder_value.inner_matches,
+                        file_src,
+                        range.start(),
+                    );
                     edit.apply(&mut matched_text);
                     out.push_str(&matched_text);
                 } else {

crates/ra_ssr/src/tests.rs

@@ -606,3 +606,20 @@ fn replace_within_macro_expansion() {
             fn f() {macro1!(bar(5.x()).o2())}"#,
     )
 }
+
+#[test]
+fn preserves_whitespace_within_macro_expansion() {
+    assert_ssr_transform(
+        "$a + $b ==>> $b - $a",
+        r#"
+            macro_rules! macro1 {
+                ($a:expr) => {$a}
+            }
+            fn f() {macro1!(1   *   2 + 3 + 4}"#,
+        r#"
+            macro_rules! macro1 {
+                ($a:expr) => {$a}
+            }
+            fn f() {macro1!(4 - 3 - 1   *   2}"#,
+    )
+}