Allow specifying exclude-edges in CLI.

This involves adding the current directory to the import path, which
might possibly cause problems down the line...

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 [project]
 name = "fk-graph"
 packages = ["src/fk_graph"]
-version = "0.0.14"
+version = "0.0.15"
 authors = [
   { name="Andrew Curtis", email="[email protected]" },
   { name="John C Thomas" },

src/fk_graph/cli.py

@@ -1,5 +1,8 @@
 from argparse import ArgumentParser, ArgumentTypeError
+from importlib import import_module
 from json import JSONDecodeError, loads
+from os import getcwd
+from sys import path
 
 from sqlalchemy import create_engine
 
@@ -17,7 +20,9 @@ def main():
         engine,
         args.table,
         args.primary_key,
-        only_tables=args.only_tables)
+        only_tables=args.only_tables,
+        exclude_edge=args.exclude_edge,
+    )
     run_app(graph)
 
 def _parse_args():
@@ -39,6 +44,14 @@ def _parse_args():
         type=_to_list,
         help="A list-like JSON string of tables to include.",
     )
+    parser.add_argument(
+        "--exclude-edge",
+        type=_to_function,
+        help=(
+            "Function to exclude edges. This should be in the form"
+            " 'path.to.module.function'"
+        ),
+    )
     args = parser.parse_args()
     if (
         (not args.demo and args.connection_string is None)
@@ -61,3 +74,9 @@ def _to_list(json_input):
     if not isinstance(parsed, list):
         raise argument_type_error
     return parsed
+
+def _to_function(function_name):
+    path.append(getcwd())
+    module, function = ".".join(function_name.split(".")[:-1]), function_name.split(".")[-1]
+    return getattr(import_module(module), function)
+

tests/fixtures/test_excluders.py

@@ -0,0 +1,3 @@
+from fk_graph.edge_excluders import input_row_is_in_tables
+
+input_row_is_in_table_a = input_row_is_in_tables(["table_a"])

tests/test_cli.py

@@ -1,3 +1,4 @@
+from pathlib import Path
 from shlex import split as shlex_split
 from subprocess import PIPE, Popen, run
 from unittest import TestCase
@@ -119,3 +120,24 @@ def test_errors_if_only_tables_is_not_listlike_json(self):
             "The --only-tables argument should be a list-like JSON string.",
             completed_process.stderr
         )
+
+    def test_can_pass_in_function_to_exclude_edges(self):
+        path = Path(".") / "tests" / "fixtures"
+        command = (
+            "fk-graph"
+            " --demo"
+            " --table=table_a"
+            " --primary-key=1"
+            " --exclude-edge='test_excluders.input_row_is_in_table_a'"
+        )
+        # PIPE just stops stdout from printing to screen.
+        process = Popen(
+            shlex_split(command),
+            stdout=PIPE,
+            cwd=path
+        )
+        self.addCleanup(process.terminate)
+        response = self.session.get("http://localhost:8050")
+        # Because of the javascripty-nature of the app, we can
+        # only really inspect the status code.
+        self.assertEqual(response.status_code, 200)