Improve file diff using Facts

Author: jgelens

pyinfra/facts/files.py

@@ -534,3 +534,18 @@ def process(self, output):
         if output and (output[0] == f"{MISSING}{self.path}"):
             return None
         return output
+
+
+class FileContents(FactBase):
+    """
+    Returns the contents of a file as a list of lines. Works with both sha1sum and sha1. Returns
+    ``None`` if the file doest not exist.
+    """
+
+    @override
+    def command(self, path):
+        return make_formatted_string_command("cat {0}", QuoteString(path))
+
+    @override
+    def process(self, output):
+        return output

pyinfra/operations/files.py

@@ -10,7 +10,7 @@
 import traceback
 from datetime import timedelta
 from fnmatch import fnmatch
-from io import BytesIO, StringIO
+from io import StringIO
 from pathlib import Path
 from typing import IO, Any, Union
 
@@ -47,6 +47,7 @@
     Block,
     Directory,
     File,
+    FileContents,
     FindFiles,
     FindInFile,
     Flags,
@@ -942,11 +943,13 @@ def put(
     # File exists, check sum and check user/group/mode if supplied
     else:
         if not _file_equal(local_sum_path, dest):
-            current_contents = BytesIO()
-
             # Generate diff when contents change
-            host.get_file(dest, current_contents)
-            current_lines = current_contents.getvalue().decode("utf-8").splitlines(keepends=True)
+            current_contents = host.get_fact(FileContents, path=dest)
+            if current_contents:
+                current_lines = [line + "\n" for line in current_contents]
+            else:
+                current_lines = []
+
             logger.info(f"\n    Will modify {click.style(dest, bold=True)}")
 
             with get_file_io(src, "r") as f:

tests/facts/files.FileContents/file.json

@@ -0,0 +1,6 @@
+{
+    "arg": "myfile",
+    "command": "cat myfile",
+    "output": ["line1", "line2"],
+    "fact": ["line1", "line2"]
+}

tests/facts/files.FileContents/no_file.json

@@ -0,0 +1,6 @@
+{
+    "arg": ["test"],
+    "command": "cat test",
+    "output": null,
+    "fact": null
+}

tests/operations/files.put/different_remote.json

@@ -24,6 +24,9 @@
         },
         "files.Sha1File": {
             "path=/home/somefile.txt": "nowt"
+        },
+        "files.FileContents": {
+            "path=/home/somefile.txt": []
         }
     },
     "commands": [

tests/operations/server.user/keys_delete.json

@@ -44,6 +44,9 @@
         "files.Sha256File": {
             "path=homedir/.ssh/authorized_keys": null
         },
+        "files.FileContents": {
+            "path=homedir/.ssh/authorized_keys": null 
+        },
         "server.Groups": {}
     },
     "commands": [