Avoid extra newline between diagnostics in grouped mode (#4776)

crates/ruff/src/message/grouped.rs

@@ -74,8 +74,13 @@ impl Emitter for GroupedEmitter {
                     }
                 )?;
             }
+
+            // Print a blank line between files, unless we're showing the source, in which case
+            // we'll have already printed a blank line between messages.
+            if !self.show_source {
                 writeln!(writer)?;
             }
+        }
 
         Ok(())
     }
@@ -136,11 +141,9 @@ impl Display for DisplayGroupedMessage<'_> {
         if self.show_source {
             use std::fmt::Write;
             let mut padded = PadAdapter::new(f);
-            write!(padded, "{}", MessageCodeFrame { message })?;
+            writeln!(padded, "{}", MessageCodeFrame { message })?;
         }
 
-        writeln!(f)?;
-
         Ok(())
     }
 }
@@ -185,6 +188,14 @@ mod tests {
 
     #[test]
     fn default() {
+        let mut emitter = GroupedEmitter::default();
+        let content = capture_emitter_output(&mut emitter, &create_messages());
+
+        assert_snapshot!(content);
+    }
+
+    #[test]
+    fn show_source() {
         let mut emitter = GroupedEmitter::default().with_show_source(true);
         let content = capture_emitter_output(&mut emitter, &create_messages());
 

crates/ruff/src/message/snapshots/ruff__message__grouped__tests__default.snap

@@ -4,30 +4,9 @@ expression: content
 ---
 fib.py:
   1:8 F401 `os` imported but unused
-    |
-  1 | import os
-    |        ^^ F401
-    |
-    = help: Remove unused import: `os`
-
   6:5 F841 Local variable `x` is assigned to but never used
-     |
-   6 | def fibonacci(n):
-   7 |     """Compute the nth number in the Fibonacci sequence."""
-   8 |     x = 1
-     |     ^ F841
-   9 |     if n == 0:
-  10 |         return 0
-     |
-     = help: Remove assignment to unused variable `x`
-
 
 undef.py:
   1:4 F821 Undefined name `a`
-    |
-  1 | if a == 1: pass
-    |    ^ F821
-    |
-
 
 

crates/ruff/src/message/snapshots/ruff__message__grouped__tests__fix_status.snap

@@ -21,7 +21,6 @@ fib.py:
      |
      = help: Remove assignment to unused variable `x`
   
-
 undef.py:
   1:4 F821 Undefined name `a`
     |
@@ -30,4 +29,3 @@ undef.py:
     |
   
 
-

crates/ruff/src/message/snapshots/ruff__message__grouped__tests__show_source.snap

@@ -0,0 +1,31 @@
+---
+source: crates/ruff/src/message/grouped.rs
+expression: content
+---
+fib.py:
+  1:8 F401 `os` imported but unused
+    |
+  1 | import os
+    |        ^^ F401
+    |
+    = help: Remove unused import: `os`
+  
+  6:5 F841 Local variable `x` is assigned to but never used
+     |
+   6 | def fibonacci(n):
+   7 |     """Compute the nth number in the Fibonacci sequence."""
+   8 |     x = 1
+     |     ^ F841
+   9 |     if n == 0:
+  10 |         return 0
+     |
+     = help: Remove assignment to unused variable `x`
+  
+undef.py:
+  1:4 F821 Undefined name `a`
+    |
+  1 | if a == 1: pass
+    |    ^ F821
+    |
+  
+