Fix for #453 - error writing diff output to file. Added test

kart/base_diff_writer.py

@@ -1,5 +1,6 @@
 import itertools
 import logging
+from pathlib import Path
 import re
 import sys
 
@@ -83,7 +84,9 @@ def __init__(
 
         self.all_ds_paths = sorted(list(all_ds_paths))
 
-        self.output_path = self._check_output_path(repo, output_path)
+        self.output_path = self._check_output_path(
+            repo, self._normalize_output_path(output_path)
+        )
 
         self.json_style = json_style
         self.target_crs = target_crs
@@ -97,6 +100,16 @@ def include_target_commit_as_header(self):
         """
         self.commit = self.target_rs.commit
 
+    @classmethod
+    def _normalize_output_path(cls, output_path):
+        if not output_path or output_path == "-":
+            return output_path
+        if isinstance(output_path, str):
+            output_path = Path(output_path)
+        if isinstance(output_path, Path):
+            output_path = output_path.expanduser()
+        return output_path
+
     @classmethod
     def _check_output_path(cls, repo, output_path):
         """Make sure the given output_path is valid for this implementation (ie, are directories supported)."""

kart/output_util.py

@@ -233,6 +233,11 @@ def resolve_output_path(output_path):
       * a file-like object
       * the string '-' or None (both will return sys.stdout)
     """
+    if (not output_path) or output_path == "-":
+        return sys.stdout
+
+    if isinstance(output_path, str):
+        output_path = Path(output_path)
     if isinstance(output_path, Path):
         output_path = output_path.expanduser()
 
@@ -241,8 +246,7 @@ def resolve_output_path(output_path):
         # but in some circumstances it can be something else.
         # e.g. click on windows may wrap it with a colorama.ansitowin32.StreamWrapper.
         return output_path
-    elif (not output_path) or output_path == "-":
-        return sys.stdout
+
     else:
         return output_path.open("w")
 

tests/test_diff.py

@@ -1638,3 +1638,15 @@ def override_get_feature(self, *args, **kwargs):
             expected_calls += 1
             assert old.get_feature_calls == expected_calls
             assert new.get_feature_calls == expected_calls
+
+
+@pytest.mark.parametrize(
+    "output_format", [o for o in DIFF_OUTPUT_FORMATS if o not in {"html", "quiet"}]
+)
+def test_diff_output_to_file(output_format, data_archive, cli_runner):
+    with data_archive("points") as repo_path:
+        r = cli_runner.invoke(
+            ["show", f"--output-format={output_format}", "--output=out"]
+        )
+        assert r.exit_code == 0, r
+        assert (repo_path / "out").exists()