Show file size before/after on binary files

Author: Wilfred

CHANGELOG.md

@@ -11,6 +11,11 @@ binary files were treated as text.
 Added the `--override-binary` option to force files to be treated as
 binary rather than text.
 
+### Display
+
+When diffing binary files, the file sizes are now shown to help see
+big changes.
+
 ## 0.64 (released 16th June 2025)
 
 ### Parsing

src/display/json.rs

@@ -156,7 +156,7 @@ impl<'f> From<&'f DiffResult> for File<'f> {
                 File::with_sections(&summary.file_format, &summary.display_path, chunks)
             }
             (FileContent::Binary, FileContent::Binary) => {
-                let status = if summary.has_byte_changes {
+                let status = if summary.has_byte_changes.is_some() {
                     Status::Changed
                 } else {
                     Status::Unchanged

src/main.rs

@@ -407,6 +407,11 @@ fn diff_file(
         guess_content(&rhs_bytes, rhs_path, binary_overrides),
     ) {
         (ProbableFileKind::Binary, _) | (_, ProbableFileKind::Binary) => {
+            let has_byte_changes = if lhs_bytes == rhs_bytes {
+                None
+            } else {
+                Some((lhs_bytes.len(), rhs_bytes.len()))
+            };
             return DiffResult {
                 extra_info: renamed,
                 display_path: display_path.to_owned(),
@@ -416,7 +421,7 @@ fn diff_file(
                 lhs_positions: vec![],
                 rhs_positions: vec![],
                 hunks: vec![],
-                has_byte_changes: lhs_bytes != rhs_bytes,
+                has_byte_changes,
                 has_syntactic_changes: false,
             };
         }
@@ -549,7 +554,11 @@ fn check_only_text(
     lhs_src: &str,
     rhs_src: &str,
 ) -> DiffResult {
-    let has_changes = lhs_src != rhs_src;
+    let has_byte_changes = if lhs_src == rhs_src {
+        None
+    } else {
+        Some((lhs_src.as_bytes().len(), rhs_src.as_bytes().len()))
+    };
 
     DiffResult {
         display_path: display_path.to_owned(),
@@ -560,8 +569,8 @@ fn check_only_text(
         lhs_positions: vec![],
         rhs_positions: vec![],
         hunks: vec![],
-        has_byte_changes: has_changes,
-        has_syntactic_changes: has_changes,
+        has_byte_changes,
+        has_syntactic_changes: lhs_src != rhs_src,
     }
 }
 
@@ -601,7 +610,7 @@ fn diff_file_content(
             lhs_positions: vec![],
             rhs_positions: vec![],
             hunks: vec![],
-            has_byte_changes: false,
+            has_byte_changes: None,
             has_syntactic_changes: false,
         };
     }
@@ -633,6 +642,13 @@ fn diff_file_content(
                         Ok((lhs, rhs)) => {
                             if diff_options.check_only {
                                 let has_syntactic_changes = lhs != rhs;
+
+                                let has_byte_changes = if lhs_src == rhs_src {
+                                    None
+                                } else {
+                                    Some((lhs_src.as_bytes().len(), rhs_src.as_bytes().len()))
+                                };
+
                                 return DiffResult {
                                     extra_info,
                                     display_path: display_path.to_owned(),
@@ -642,7 +658,7 @@ fn diff_file_content(
                                     lhs_positions: vec![],
                                     rhs_positions: vec![],
                                     hunks: vec![],
-                                    has_byte_changes: true,
+                                    has_byte_changes,
                                     has_syntactic_changes,
                                 };
                             }
@@ -775,6 +791,12 @@ fn diff_file_content(
     );
     let has_syntactic_changes = !hunks.is_empty();
 
+    let has_byte_changes = if lhs_src == rhs_src {
+        None
+    } else {
+        Some((lhs_src.as_bytes().len(), rhs_src.as_bytes().len()))
+    };
+
     DiffResult {
         extra_info,
         display_path: display_path.to_owned(),
@@ -784,7 +806,7 @@ fn diff_file_content(
         lhs_positions,
         rhs_positions,
         hunks,
-        has_byte_changes: true,
+        has_byte_changes,
         has_syntactic_changes,
     }
 }
@@ -923,7 +945,7 @@ fn print_diff_result(display_options: &DisplayOptions, summary: &DiffResult) {
             }
         }
         (FileContent::Binary, FileContent::Binary) => {
-            if display_options.print_unchanged || summary.has_byte_changes {
+            if display_options.print_unchanged || summary.has_byte_changes.is_some() {
                 println!(
                     "{}",
                     display::style::header(
@@ -935,10 +957,17 @@ fn print_diff_result(display_options: &DisplayOptions, summary: &DiffResult) {
                         display_options
                     )
                 );
-                if summary.has_byte_changes {
-                    println!("Binary contents changed.\n");
-                } else {
-                    println!("No changes.\n");
+
+                match summary.has_byte_changes {
+                    Some((lhs_len, rhs_len)) => {
+                        let format_options = FormatSizeOptions::from(BINARY).decimal_places(1);
+                        println!(
+                            "Binary contents changed (old: {}, new: {}).\n",
+                            &format_size(lhs_len, format_options),
+                            &format_size(rhs_len, format_options),
+                        )
+                    }
+                    None => println!("No changes.\n"),
                 }
             }
         }

src/summary.rs

@@ -50,7 +50,9 @@ pub(crate) struct DiffResult {
     pub(crate) lhs_positions: Vec<MatchedPos>,
     pub(crate) rhs_positions: Vec<MatchedPos>,
 
-    pub(crate) has_byte_changes: bool,
+    /// If the two files do not have exactly the same bytes, the
+    /// number of bytes in each file.
+    pub(crate) has_byte_changes: Option<(usize, usize)>,
     pub(crate) has_syntactic_changes: bool,
 }
 
@@ -59,7 +61,7 @@ impl DiffResult {
         if matches!(self.lhs_src, FileContent::Binary)
             || matches!(self.rhs_src, FileContent::Binary)
         {
-            return self.has_byte_changes;
+            return self.has_byte_changes.is_some();
         }
 
         self.has_syntactic_changes