postprocess: use rich to pretty-print the diff

Author: kkysen

c2rust-postprocess/postprocess/__init__.py

@@ -154,7 +154,8 @@ def main(argv: Sequence[str] | None = None):
                 break
 
         for failure in failures:
-            print(f"{failure}\n")
+            failure.print()
+            print()
 
         if failures:
             print(f"""\

c2rust-postprocess/postprocess/transforms.py

@@ -8,6 +8,8 @@
 from textwrap import dedent
 
 import yaml
+from rich.console import Console
+from rich.syntax import Syntax
 
 from postprocess.cache import AbstractCache
 from postprocess.definitions import (
@@ -87,7 +89,7 @@ def header(self) -> str:
         )
 
     def diff(self) -> str:
-        diff = "".join(
+        return "".join(
             unified_diff(
                 a=[f"{comment}\n" for comment in self.c_comments],
                 b=[f"{comment}\n" for comment in self.rust_comments],
@@ -96,13 +98,23 @@ def diff(self) -> str:
                 tofile=f"{self.prompt.rust_source_file}:{self.prompt.identifier}",
             )
         ).rstrip()
+
+    def __str__(self) -> str:
         return f"""\
+{self.header()}
+
 ```diff
-{diff}
+{self.diff()}
 ```"""
 
-    def __str__(self) -> str:
-        return f"{self.header()}\n\n{self.diff()}"
+    def print(self):
+        console = Console()
+        console.print(f"""\
+{self.header()}
+
+```diff""")
+        console.print(Syntax(self.diff(), "diff"))
+        console.print("```")
 
     @staticmethod
     def to_exclude_file(failures: Iterable["CommentTransferFailure"]) -> str:

c2rust-postprocess/pyproject.toml

@@ -9,6 +9,7 @@ dependencies = [
     "platformdirs>=4.5.1",
     "pygments>=2.19.2",
     "pyyaml>=6.0.3",
+    "rich>=14.2.0",
     "tomli>=2.3.0",
     "tomlkit>=0.13.3",
     "tree-sitter>=0.25.2",