File associations

changes/2284.feature.rst

@@ -0,0 +1 @@
+Added improved document types (file associations) for Windows and macOS platforms

src/briefcase/config.py

@@ -146,6 +146,22 @@ def validate_document_type_config(document_type_id, document_type):
             f"The URL associated with document type {document_type_id!r} is invalid: {e}"
         )
 
+    if sys.platform == "darwin":
+        from briefcase.platforms.macOS.utils import mime_type_to_UTI
+
+        macOS = document_type.setdefault("macOS", {})
+        if (UTI := mime_type_to_UTI(document_type.get("mime_type", None))) is not None:
+            macOS.setdefault("LSItemContentType", UTI)
+            macOS.setdefault("LSHandlerRank", "Alternate")
+            macOS.setdefault("UTTypeConformsTo", ["public.xyz"])
+        else:
+            # LSItemContentType will default to bundle.app_name.document_type_id
+            # in the Info.plist template if it is not provided.
+            macOS.setdefault("LSHandlerRank", "Owner")
+            macOS.setdefault("UTTypeConformsTo", ["public.data", "public.content"])
+
+        macOS.setdefault("CFBundleTypeRole", "Viewer")
+
 
 VALID_BUNDLE_RE = re.compile(r"[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)+$")
 

src/briefcase/platforms/macOS/utils.py

@@ -3,6 +3,8 @@
 import concurrent
 import email
 import hashlib
+import pathlib
+import plistlib
 import subprocess
 from pathlib import Path
 
@@ -272,3 +274,48 @@ def merge_app_packages(
                             raise future.exception()
         else:
             self.console.info("No libraries require merging.")
+
+
+def mime_type_to_UTI(mime_type: str) -> str | None:
+    """Convert a MIME type to a Uniform Type Identifier (UTI).
+
+    This function reads the system's CoreTypes Info.plist file to determine the
+    UTI for a given MIME type.
+
+    Args:
+        mime_type: The MIME type to convert.
+
+    Returns:
+        The UTI for the MIME type, or None if the UTI cannot be determined.
+    """
+    plist_data = pathlib.Path(
+        "/System/Library/CoreServices/CoreTypes.bundle/Contents/Info.plist"
+    ).read_bytes()
+    plist = plistlib.loads(plist_data)
+    for type_declaration in (
+        plist["UTExportedTypeDeclarations"] + plist["UTImportedTypeDeclarations"]
+    ):
+        # We check both the system built-in types (exported) and the known
+        # third-party types (imported) to find the UTI for the given MIME type.
+        # Most type declarations will have a UTTypeTagSpecification dictionary
+        # with a "public.mime-type" key. That can be either a list of MIME types
+        # or a single MIME type. We check if the MIME type is in the list or
+        # matches the single MIME type. If we find a match, we return the UTI
+        # identifier. If we don't find a match, we return None.
+
+        mime_types = type_declaration.get("UTTypeTagSpecification", {}).get(
+            "public.mime-type", []
+        )
+        if isinstance(mime_types, list):
+            # Most MIME types are declared as a list even if they are a
+            # single type. Some types define multiple closely-related MIME
+            # types.
+            if mime_type in mime_types:
+                return type_declaration["UTTypeIdentifier"]
+        else:
+            # some MIME types are declared as a single type
+            if mime_types == mime_type:
+                return type_declaration["UTTypeIdentifier"]
+
+    # If no match is found in the entire list, return None
+    return None

tests/config/test_AppConfig.py

@@ -84,6 +84,14 @@ def test_extra_attrs():
             "extension": "doc",
             "description": "A document",
             "url": "https://testurl.com",
+            "macOS": {
+                "CFBundleTypeRole": "Viewer",
+                "LSHandlerRank": "Owner",
+                "UTTypeConformsTo": [
+                    "public.data",
+                    "public.content",
+                ],
+            },
         }
     }