summon: ugly hack

dvc/api.py

@@ -1,4 +1,5 @@
 import os
+import importlib.util
 from contextlib import contextmanager
 
 try:
@@ -6,6 +7,8 @@ try:
 except ImportError:
     from contextlib import GeneratorContextManager as GCM
 
+import ruamel.yaml
+
 from dvc.utils.compat import urlparse
 from dvc.repo import Repo
 from dvc.external_repo import external_repo
@@ -69,3 +72,37 @@ def _make_repo(repo_url, rev=None):
     else:
         with external_repo(url=repo_url, rev=rev) as repo:
             yield repo
+
+
+def summon(name, repo=None, rev=None):
+    # 1. Read artifacts.yaml
+    # 2. Pull dependencies
+    # 3. Get the call and parameters
+    # 4. Invoke the call with the given parameters
+    # 5. Return the result
+
+    with _make_repo(repo, rev=rev) as _repo:
+        artifacts_path = os.path.join(_repo.root_dir, "artifacts.yaml")
+
+        with _repo.open(artifacts_path, mode="r") as fd:
+            artifacts = ruamel.yaml.load(fd.read()).get("artifacts")
+
+        artifact = next(x for x in artifacts if x.get("name") == name)
+
+        spec = importlib.util.spec_from_file_location(
+            artifact.get("call"),
+            os.path.join(_repo.root_dir, artifact.get("file")),
+        )
+
+        module = importlib.util.module_from_spec(spec)
+
+        # ugly af, don't use exec / global, pls
+        call = 'global result; result = {method}({params})'.format(
+            method=artifact.get("call"),
+            params=", ".join(k + "=" + v for k, v in artifact.get("params").items())
+        )
+
+        spec.loader.exec_module(module)
+        exec(call)
+        global result
+        return result

tests/func/test_api.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 import os
 import shutil
 
+import ruamel.yaml
 import pytest
 
 from dvc import api
@@ -126,3 +127,25 @@ def test_open_not_cached(dvc):
     os.remove(metric_file)
     with pytest.raises(FileMissingError):
         api.read(metric_file)
+
+
+def test_summon(tmp_dir, erepo_dir, dvc):
+    artifacts_yaml = ruamel.yaml.dump({
+        "artifacts": [{
+            "name": "sum",
+            "description": "The sum of 1 + 2",
+            "call": "module.sum",
+            "file": "module.py",
+            "params": {"x": "1", "y": "2"},
+            "deps": ["foo"],
+        }]
+    })
+
+    erepo_dir.gen("module.py", "def sum(x, y): return x + y")
+    erepo_dir.gen("artifacts.yaml", artifacts_yaml)
+    erepo_dir.scm.add(["module.py", "artifacts.yaml"])
+    erepo_dir.scm.commit("Add module.py and artifacts.yaml")
+
+    repo_url = "file://{}".format(erepo_dir)
+
+    assert api.summon("sum", repo=repo_url) == 3