[fix] indentation & trailing whitespace in Heredoc

.github/workflows/ci.yml

@@ -51,6 +51,9 @@ jobs:
     - uses: actions/checkout@v6
       with:
         submodules: true
+    - uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: '3.4'
     - if: runner.os == 'macOS'
       uses: actions-rust-lang/setup-rust-toolchain@v1
       with:

fixtures/small/heredoc_indented_whitespace_expected.rb

@@ -1,15 +1,15 @@
 def foo
   <<~THING
-    awfweaf
+    awfweaf 
       awefawef
-
-
-
+      
+      
+      
     hi there
   THING
 
   <<-THING
-
+  
   hi there
   THING
 end

librubyfmt/src/format_prism.rs

@@ -931,9 +931,12 @@ fn format_inner_string<'src>(
                         .count()
                         - escaped_ws_count;
 
+                    let raw_leading_cols = count_indent_cols(&raw[..raw_leading]);
+                    let unescaped_leading_cols = count_indent_cols(&unescaped[..unescaped_leading]);
+
                     // The difference is the common indent (if raw has more leading whitespace)
-                    if raw_leading > unescaped_leading {
-                        return Some(raw_leading - unescaped_leading);
+                    if raw_leading_cols > unescaped_leading_cols {
+                        return Some(raw_leading_cols - unescaped_leading_cols);
                     }
                 }
                 None
@@ -960,11 +963,10 @@ fn format_inner_string<'src>(
                             .enumerate()
                             .map(|(line_idx, line)| {
                                 // Strip from lines at line boundaries
-                                let should_strip = (line_idx > 0 || prev_ended_with_newline)
-                                    && !line.is_empty()
-                                    && line.len() >= common_indent;
+                                let should_strip =
+                                    (line_idx > 0 || prev_ended_with_newline) && !line.is_empty();
                                 if should_strip {
-                                    &line[common_indent..]
+                                    strip_indent_cols(line, common_indent)
                                 } else {
                                     line
                                 }
@@ -5167,3 +5169,42 @@ fn format_write_node<'src>(
     ps.emit_space();
     ps.with_start_of_line(false, |ps| format_node(ps, value));
 }
+
+/// Count leading whitespace columns. Tabs advance to the next multiple of 8.
+fn count_indent_cols(line: &[u8]) -> usize {
+    let mut col = 0;
+    for &b in line {
+        match b {
+            b' ' => col += 1,
+            b'\t' => col = (col / 8 + 1) * 8,
+            _ => break,
+        }
+    }
+    col
+}
+
+/// Strip up to `cols` leading whitespace columns from `line`.
+/// Tabs advance to the next multiple of 8.
+/// If a tab would advance past `cols`, it is not stripped.
+fn strip_indent_cols(line: &[u8], cols: usize) -> &[u8] {
+    let mut col = 0;
+    let mut i = 0;
+    while i < line.len() && col < cols {
+        match line[i] {
+            b' ' => {
+                col += 1;
+                i += 1;
+            }
+            b'\t' => {
+                col = (col / 8 + 1) * 8;
+                if col > cols {
+                    // We are in the middle of a tab. Do not strip it.
+                    break;
+                }
+                i += 1;
+            }
+            _ => break,
+        }
+    }
+    &line[i..]
+}

librubyfmt/src/heredoc_string.rs

@@ -68,8 +68,16 @@ impl<'src> HeredocString<'src> {
         let indent = self.indent;
 
         if self.kind.is_squiggly() {
-            // For squiggly heredocs, we need to apply indentation to Normal segments
-            // but not to Raw segments (which come from nested non-squiggly heredocs).
+            // Do not indent raw segments (nested non-squiggly heredocs).
+            // Do not indent when all normal segments contain only whitespace.
+            let should_indent = self.segments.iter().any(|seg| {
+                if let HeredocSegment::Normal(c) = seg {
+                    c.iter().any(|&b| b != b' ' && b != b'\t' && b != b'\n')
+                } else {
+                    false
+                }
+            });
+
             let mut result = Vec::new();
             for segment in self.segments {
                 match segment {
@@ -79,9 +87,10 @@ impl<'src> HeredocString<'src> {
                             if i > 0 {
                                 result.push(b'\n');
                             }
-                            let mut indented = get_indent(indent as usize + 2).into_owned();
-                            indented.extend_from_slice(line);
-                            result.extend_from_slice(indented.trim_ascii_end());
+                            if !line.is_empty() && should_indent {
+                                result.extend_from_slice(get_indent(indent as usize + 2).as_ref());
+                            }
+                            result.extend_from_slice(line);
                         }
                     }
                     HeredocSegment::Raw(content) => {
@@ -90,14 +99,14 @@ impl<'src> HeredocString<'src> {
                             if i > 0 {
                                 result.push(b'\n');
                             }
-                            result.extend_from_slice(line.trim_ascii_end());
+                            result.extend_from_slice(line);
                         }
                     }
                 }
             }
             result
         } else {
-            // For non-squiggly heredocs, just join segments and trim line endings
+            // For non-squiggly heredocs, just join segments
             let mut result = Vec::new();
             for segment in self.segments {
                 let content = match segment {
@@ -107,7 +116,7 @@ impl<'src> HeredocString<'src> {
                     if i > 0 {
                         result.push(b'\n');
                     }
-                    result.extend_from_slice(line.trim_ascii_end());
+                    result.extend_from_slice(line);
                 }
             }
             result