fix(remove): Carry comments across removes

Author: epage

src/cargo/util/toml_mut/manifest.rs

@@ -540,5 +540,42 @@ fn non_existent_dependency_err(
 }
 
 fn remove_array_index(array: &mut toml_edit::Array, index: usize) {
-    array.remove(index);
+    let value = array.remove(index);
+
+    // Captures all lines before leading whitespace
+    let prefix_lines = value
+        .decor()
+        .prefix()
+        .and_then(|p| p.as_str().expect("spans removed").rsplit_once('\n'))
+        .map(|(lines, _current)| lines);
+    // Captures all lines after trailing whitespace, before the next comma
+    let suffix_lines = value
+        .decor()
+        .suffix()
+        .and_then(|p| p.as_str().expect("spans removed").split_once('\n'))
+        .map(|(_current, lines)| lines);
+    let mut merged_lines = String::new();
+    if let Some(prefix_lines) = prefix_lines {
+        merged_lines.push_str(prefix_lines);
+        merged_lines.push('\n');
+    }
+    if let Some(suffix_lines) = suffix_lines {
+        merged_lines.push_str(suffix_lines);
+        merged_lines.push('\n');
+    }
+
+    let next_index = index; // Since `index` was removed, that effectively auto-advances us
+    if let Some(next) = array.get_mut(next_index) {
+        let next_decor = next.decor_mut();
+        let next_prefix = next_decor
+            .prefix()
+            .map(|s| s.as_str().expect("spans removed"))
+            .unwrap_or_default();
+        merged_lines.push_str(next_prefix);
+        next_decor.set_prefix(merged_lines);
+    } else {
+        let trailing = array.trailing().as_str().expect("spans removed");
+        merged_lines.push_str(trailing);
+        array.set_trailing(merged_lines);
+    }
 }

tests/testsuite/cargo_remove/optional_dep_feature_formatting/out/Cargo.toml

@@ -21,7 +21,10 @@ serde = "1.0.90"
 [features]
 std = [
   # Leading clippy
-  "dep:clippy",  # trailing docopt
+  "dep:clippy",  # trailing clippy
+
+  # Leading docopt
+  # trailing docopt
 
   # Leading rustc-serialize
   "dep:rustc-serialize",  # trailing rustc-serialize
@@ -30,5 +33,8 @@ std = [
   "serde/std",  # trailing serde/std
 
   # Leading semver/std
-  "semver/std",  # trailing toml
+  "semver/std",  # trailing semver/std
+
+  # Leading toml
+  # trailing toml
 ]