Prompt user whether to replace file contents

pasch/__init__.py

@@ -1,10 +1,10 @@
-from . import cmd, file, modules
+from . import file, modules, util
 from .orchestrator import Module, Orchestrator
 
 __all__: list[str] = [
     "Module",
     "Orchestrator",
-    "cmd",
     "file",
     "modules",
+    "util",
 ]

pasch/cmd.py

@@ -1,16 +0,0 @@
-import shlex
-import subprocess
-
-from rich import print
-from rich.markup import escape
-
-
-def run_execute(*cmd: str) -> None:
-    print(f"[bright_black]$ {escape(shlex.join(cmd))}")
-    subprocess.run(cmd, check=True)
-
-
-def run_capture(*cmd: str) -> str:
-    print(f"[bright_black]$ {escape(shlex.join(cmd))}")
-    result = subprocess.run(cmd, check=True, capture_output=True, encoding="utf-8")
-    return result.stdout

pasch/modules/echo.py

@@ -1,5 +1,5 @@
-from pasch.cmd import run_execute
 from pasch.orchestrator import Module, Orchestrator
+from pasch.util import run_execute
 
 
 class Echo(Module):

pasch/modules/files.py

@@ -4,10 +4,12 @@ import random
 import string
 from pathlib import Path
 
+from rich.console import Console
 from rich.markup import escape
 
 from pasch.file.file import File
 from pasch.orchestrator import Module, Orchestrator
+from pasch.util import fmt_diff, prompt
 
 
 def random_tmp_path(path: Path) -> Path:
@@ -42,6 +44,21 @@ def path_to_str(path: Path) -> str:
     return str(path.resolve())
 
 
+def diff_and_prompt(c: Console, path: Path, new_content_bytes: bytes) -> bool:
+    try:
+        new_content = new_content_bytes.decode("utf-8")
+    except:
+        return False
+
+    try:
+        old_content = path.read_text(encoding="utf-8")
+    except:
+        return False
+
+    c.print(fmt_diff(old_content, new_content))
+    return prompt("Replace file contents?", default=False)
+
+
 class FileDb:
     def __init__(self, path: Path) -> None:
         self._path = path
@@ -128,7 +145,8 @@ class Files(Module):
 
         if reason := self._file_db.verify_hash(path, cur_hash):
             self.c.print(f"[red]Error:[/] {escape(reason)}")
-            return
+            if not diff_and_prompt(self.c, path, content):
+                return
 
         # We want to avoid scenarios where we fail to remember a file we've
         # written. It is better to remember a file with an incorrect hash than

pasch/modules/pacman.py

@@ -3,8 +3,8 @@ from subprocess import CalledProcessError
 
 from rich.markup import escape
 
-from pasch.cmd import run_capture, run_execute
 from pasch.orchestrator import Module, Orchestrator
+from pasch.util import run_capture, run_execute
 
 
 @dataclass

pasch/util.py

@@ -0,0 +1,44 @@
+import difflib
+import shlex
+import subprocess
+
+from rich import print
+from rich.markup import escape
+from rich.syntax import Syntax
+
+
+def run_execute(*cmd: str) -> None:
+    print(f"[bright_black]$ {escape(shlex.join(cmd))}")
+    subprocess.run(cmd, check=True)
+
+
+def run_capture(*cmd: str) -> str:
+    print(f"[bright_black]$ {escape(shlex.join(cmd))}")
+    result = subprocess.run(cmd, check=True, capture_output=True, encoding="utf-8")
+    return result.stdout
+
+
+def fmt_diff(old: str, new: str, old_name="old", new_name="new") -> Syntax:
+    diff_text = "".join(
+        difflib.unified_diff(
+            old.splitlines(keepends=True),
+            new.splitlines(keepends=True),
+            fromfile=old_name,
+            tofile=new_name,
+            lineterm="\n",
+        )
+    )
+    return Syntax(diff_text, "diff", line_numbers=False)
+
+
+def prompt(question: str, default: bool | None = None) -> bool:
+    default_str = {True: "[Y/n]", False: "[y/N]", None: "[y/n]"}[default]
+    while True:
+        reply = input(f"{question} {default_str} ").strip().lower()
+        if not reply and default is not None:
+            return default
+        if reply in {"y", "yes"}:
+            return True
+        if reply in {"n", "no"}:
+            return False
+        print("Please enter y/yes or n/no.")