Added function filter to template system, closes #429

osxphotos/phototemplate.py

@@ -913,42 +913,44 @@ class PhotoTemplate:
             if values and type(values) == list:
                 value = [v.lower() for v in values]
             else:
-                value = [values.lower()]
+                value = [values.lower()] if values else []
         elif filter_ == "upper":
             if values and type(values) == list:
                 value = [v.upper() for v in values]
             else:
-                value = [values.upper()]
+                value = [values.upper()] if values else []
         elif filter_ == "strip":
             if values and type(values) == list:
                 value = [v.strip() for v in values]
             else:
-                value = [values.strip()]
+                value = [values.strip()] if values else []
         elif filter_ == "capitalize":
             if values and type(values) == list:
                 value = [v.capitalize() for v in values]
             else:
-                value = [values.capitalize()]
+                value = [values.capitalize()] if values else []
         elif filter_ == "titlecase":
             if values and type(values) == list:
                 value = [v.title() for v in values]
             else:
-                value = [values.title()]
+                value = [values.title()] if values else []
         elif filter_ == "braces":
             if values and type(values) == list:
                 value = ["{" + v + "}" for v in values]
             else:
-                value = ["{" + values + "}"]
+                value = ["{" + values + "}"] if values else []
         elif filter_ == "parens":
             if values and type(values) == list:
                 value = ["(" + v + ")" for v in values]
             else:
-                value = ["(" + values + ")"]
+                value = ["(" + values + ")"] if values else []
         elif filter_ == "brackets":
             if values and type(values) == list:
                 value = ["[" + v + "]" for v in values]
             else:
-                value = ["[" + values + "]"]
+                value = ["[" + values + "]"] if values else []
+        elif filter_.startswith("function:"):
+            value = self.get_template_value_filter_function(filter_, values)
         else:
             value = []
         return value
@@ -1097,8 +1099,6 @@ class PhotoTemplate:
 
         filename, funcname = subfield.split("::")
 
-        print(filename, funcname)
-
         if not pathlib.Path(filename).is_file():
             raise ValueError(f"'{filename}' does not appear to be a file")
 
@@ -1120,6 +1120,35 @@ class PhotoTemplate:
 
         return values
 
+    def get_template_value_filter_function(self, filter_, values):
+        """Filter template value from external function """
+
+        filter_ = filter_.replace("function:","")
+
+        if "::" not in filter_:
+            raise ValueError(
+                f"SyntaxError: could not parse function name from '{filter_}'"
+            )
+
+        filename, funcname = filter_.split("::")
+
+        if not pathlib.Path(filename).is_file():
+            raise ValueError(f"'{filename}' does not appear to be a file")
+
+        template_func = load_function(filename, funcname)
+
+        if not isinstance(values, (list, tuple)):
+            values = [values]
+        values = template_func(values)
+
+        if not isinstance(values, list):
+            raise TypeError(
+                f"Invalid return type for function {funcname}: expected list"
+            )
+
+        return values
+
+
     def get_photo_video_type(self, default):
         """ return media type, e.g. photo or video """
         default_dict = parse_default_kv(default, PHOTO_VIDEO_TYPE_DEFAULTS)

osxphotos/phototemplate.tx

@@ -74,7 +74,7 @@ Filter:
 ;
 
 FILTER_WORD:
-    /[\.\w]+/
+    /[\.\w:\/]+/
 ;
 
 Conditional:

tests/template_filter.py

@@ -0,0 +1,17 @@
+""" Example of using a custom python function as an osxphotos template filter 
+
+    Use in formath:
+    "{template_field|template_filter.py::myfilter}"
+
+    Your filter function will receive a list of strings even if the template renders to a single value.  
+    You should expect a list and return a list and be able to handle multi-value templates like {keyword}
+    as well as single-value templates like {original_name}
+"""
+
+from typing import List
+
+def myfilter(values: List[str]) -> List[str]:
+    """ Custom filter to append "foo-" to template value """
+    values = ["foo-" + val for val in values]
+    return values
+

tests/test_template.py

@@ -982,3 +982,31 @@ def test_function_bad(photosdb):
             "{function:tests/template_function.py::foobar}"
         )
 
+
+def test_function_filter(photosdb):
+    """ Test {field|function} filter"""
+    photo = photosdb.get_photo(UUID_MULTI_KEYWORDS)
+
+    rendered, _ = photo.render_template(
+        "{photo.original_filename|function:tests/template_filter.py::myfilter}"
+    )
+    assert rendered == [f"foo-{photo.original_filename}"]
+
+    rendered, _ = photo.render_template(
+        "{photo.original_filename|lower|function:tests/template_filter.py::myfilter}"
+    )
+    assert rendered == [f"foo-{photo.original_filename.lower()}"]
+
+    rendered, _ = photo.render_template(
+        "{photo.original_filename|function:tests/template_filter.py::myfilter|lower}"
+    )
+    assert rendered == [f"foo-{photo.original_filename.lower()}"]
+
+
+def test_function_filter_bad(photosdb):
+    """ Test invalid {field|function} filter"""
+    photo = photosdb.get_photo(UUID_MULTI_KEYWORDS)
+    with pytest.raises(ValueError):
+        rendered, _ = photo.render_template(
+            "{photo.original_filename|function:tests/template_filter.py::foobar}"
+        )