Add option for including context before and after a label

codespan-reporting/src/term/config.rs

@@ -29,6 +29,14 @@ pub struct Config {
     ///
     /// [`Label`]: crate::diagnostic::Label
     pub end_context_lines: usize,
+    /// The minimum number of lines before a label that should be included for context.
+    ///
+    /// Defaults to: `0`.
+    pub before_label_lines: usize,
+    /// The minimum number of lines after a label that should be included for context.
+    ///
+    /// Defaults to: `0`.
+    pub after_label_lines: usize,
 }
 
 impl Default for Config {
@@ -40,6 +48,8 @@ impl Default for Config {
             chars: Chars::default(),
             start_context_lines: 3,
             end_context_lines: 1,
+            before_label_lines: 0,
+            after_label_lines: 0,
         }
     }
 }

codespan-reporting/src/term/views.rs

@@ -135,6 +135,34 @@ where
                 }
             };
 
+            let lines_before = usize::min(start_line_index, self.config.before_label_lines);
+            for offset in (1..lines_before + 1).rev() {
+                let range = files.line_range(label.file_id, start_line_index - offset);
+                if let Ok(range) = range {
+                    let line = labeled_file.get_or_insert_line(
+                        start_line_index - offset,
+                        range,
+                        start_line_number - offset,
+                    );
+                    line.must_render = true;
+                } else {
+                    break;
+                }
+            }
+            for offset in 1..lines_before + 1 {
+                let range = files.line_range(label.file_id, start_line_index + offset);
+                if let Ok(range) = range {
+                    let line = labeled_file.get_or_insert_line(
+                        end_line_index + offset,
+                        range,
+                        end_line_number + offset,
+                    );
+                    line.must_render = true;
+                } else {
+                    break;
+                }
+            }
+
             if start_line_index == end_line_index {
                 // Single line
                 //