Sketch of overriding operations based on a CLI flag

Lib/gftools/builder/__init__.py

@@ -17,7 +17,7 @@
 from ninja.ninja_syntax import Writer, escape_path
 
 from gftools.builder.file import File
-from gftools.builder.operations import OperationBase, known_operations
+from gftools.builder.operations import OperationBase, OperationRegistry
 from gftools.builder.operations.copy import Copy
 from gftools.builder.recipeproviders import get_provider
 from gftools.builder.schema import BASE_SCHEMA
@@ -36,7 +36,7 @@ class GFBuilder:
     config: dict
     recipe: Recipe
 
-    def __init__(self, config: Union[dict, str]):
+    def __init__(self, config: Union[dict, str], use_fontc = False):
         if isinstance(config, str):
             parentpath = Path(config).resolve().parent
             with open(config, "r") as file:
@@ -55,6 +55,7 @@ def __init__(self, config: Union[dict, str]):
             self._orig_config = yaml.dump(config)
             self.config = config
 
+        self.known_operations = OperationRegistry(use_fontc=use_fontc)
         self.writer = Writer(open("build.ninja", "w"))
         self.named_files = {}
         self.used_operations = set([])
@@ -156,9 +157,10 @@ def glyphs_to_ufo(self, source):
 
     def operation_step_to_object(self, step):
         operation = step.get("operation") or step.get("postprocess")
-        if operation not in known_operations:
+        cls = self.known_operations.get(operation)
+        if cls is None:
             raise ValueError(f"Unknown operation {operation}")
-        cls = known_operations[operation]
+
         if operation not in self.used_operations:
             self.used_operations.add(operation)
             cls.write_rules(self.writer)
@@ -381,6 +383,12 @@ def main(args=None):
         help="Just generate and output recipe from recipe builder",
         action="store_true",
     )
+    parser.add_argument(
+        "--experimental-fontc",
+        help="Use fontc instead of fontmake",
+        action="store_true",
+    )
+
     parser.add_argument("config", help="Path to config file or source file", nargs="+")
     args = parser.parse_args(args)
     yaml_files = []
@@ -404,7 +412,7 @@ def main(args=None):
             raise ValueError("Only one config file can be given for now")
         config = args.config[0]
 
-    pd = GFBuilder(config)
+    pd = GFBuilder(config, use_fontc = args.experimental_fontc)
     if args.generate:
         config = pd.config
         config["recipe"] = pd.recipe

Lib/gftools/builder/operations/__init__.py

@@ -8,7 +8,9 @@
 import sys
 from os.path import dirname
 from tempfile import NamedTemporaryFile
+from typing import Dict
 
+# from gftools.builder.operations.fontc import FontcBuildTTF, FontcBuildVariable
 from gftools.builder.file import File
 from gftools.utils import shell_quote
 
@@ -149,18 +151,42 @@ def variables(self):
 
         return vars
 
-
-known_operations = {}
-
-for mod in pkgutil.iter_modules([dirname(__file__)]):
-    imp = importlib.import_module("gftools.builder.operations." + mod.name)
-    classes = [
-        (name, cls)
-        for name, cls in inspect.getmembers(sys.modules[imp.__name__], inspect.isclass)
-        if "OperationBase" not in name and issubclass(cls, OperationBase)
-    ]
-    if len(classes) > 1:
-        raise ValueError(
-            f"Too many classes in module gftools.builder.operations.{mod.name}"
-        )
-    known_operations[mod.name] = classes[0][1]
+# just pretend these live elsewhere, here now for illustration
+class FontcBuildVariable(OperationBase):
+    description = "Build a variable font from a source file (with fontc)"
+    rule = "fontc -o $out $in"
+
+class FontcBuildTTF(OperationBase):
+    description = "Build a TTF from a source file (with fontc)"
+    rule = "fontc -o $out $in"
+
+class OperationRegistry:
+    def __init__(self, use_fontc: bool):
+        self.known_operations = get_known_operations()
+        if use_fontc:
+            self.known_operations["buildVariable"] = FontcBuildVariable
+            self.known_operations["buildTTF"] = FontcBuildTTF
+        print(self.known_operations, file=sys.stderr)
+
+    def get(self, operation_name: str):
+        return self.known_operations.get(operation_name)
+
+
+def get_known_operations() -> Dict[str, OperationBase]:
+    known_operations = {}
+
+    for mod in pkgutil.iter_modules([dirname(__file__)]):
+        if "fontc" in mod.name:
+            continue
+        imp = importlib.import_module("gftools.builder.operations." + mod.name)
+        classes = [
+            (name, cls)
+            for name, cls in inspect.getmembers(sys.modules[imp.__name__], inspect.isclass)
+            if "OperationBase" not in name and issubclass(cls, OperationBase)
+        ]
+        if len(classes) > 1:
+            raise ValueError(
+                f"Too many classes in module gftools.builder.operations.{mod.name}"
+            )
+        known_operations[mod.name] = classes[0][1]
+    return known_operations