run: try to save deps before running the command (#3709)

Unlike old `_check_missing_deps`, this also verifies that we are able to
save more complex dependencies such as parameters, where we not only
care about the config file, but also about the parameters in it.

Fixes #3707

dvc/stage/__init__.py

@@ -21,7 +21,6 @@
     StagePathNotDirectoryError,
     StageCommitError,
     StageUpdateError,
-    MissingDep,
     MissingDataSource,
 )
 from . import params
@@ -374,8 +373,7 @@ def is_cached(self):
 
         # NOTE: need to save checksums for deps in order to compare them
         # with what is written in the old stage.
-        for dep in self.deps:
-            dep.save()
+        self._save_deps()
 
         old_d = old.dumpd()
         new_d = self.dumpd()
@@ -482,10 +480,13 @@ def _compute_md5(self):
         logger.debug("Computed {} md5: '{}'".format(self, m))
         return m
 
-    def save(self):
+    def _save_deps(self):
         for dep in self.deps:
             dep.save()
 
+    def save(self):
+        self._save_deps()
+
         for out in self.outs:
             out.save()
 
@@ -526,12 +527,6 @@ def commit(self):
         for out in self.outs:
             out.commit()
 
-    def _check_missing_deps(self):
-        missing = [dep for dep in self.deps if not dep.exists]
-
-        if any(missing):
-            raise MissingDep(missing)
-
     @staticmethod
     def _warn_if_fish(executable):  # pragma: no cover
         if (
@@ -570,8 +565,6 @@ def _check_duplicated_arguments(self):
 
     @unlocked_repo
     def _run(self):
-        self._check_missing_deps()
-
         kwargs = {"cwd": self.wdir, "env": fix_env(None), "close_fds": True}
 
         if os.name == "nt":
@@ -667,6 +660,7 @@ def run(
                     logger.info("Stage is cached, skipping.")
                     self.checkout()
                 else:
+                    self._save_deps()
                     logger.info("Running command:\n\t{}".format(self.cmd))
                     self._run()
 

dvc/stage/exceptions.py

@@ -73,15 +73,6 @@ def __init__(self, path):
         )
 
 
-class MissingDep(DvcException):
-    def __init__(self, deps):
-        assert len(deps) > 0
-
-        dep = "dependencies" if len(deps) > 1 else "dependency"
-        msg = "missing '{}': {}".format(dep, ", ".join(map(str, deps)))
-        super().__init__(msg)
-
-
 class MissingDataSource(DvcException):
     def __init__(self, missing_files):
         assert len(missing_files) > 0

tests/func/test_run_single_stage.py

@@ -26,7 +26,6 @@
     StagePathOutsideError,
     StagePathNotFoundError,
     StagePathNotDirectoryError,
-    MissingDep,
 )
 from dvc.system import System
 from dvc.utils import file_md5
@@ -79,7 +78,9 @@ def test(self):
 
 class TestRunMissingDep(TestDvc):
     def test(self):
-        with self.assertRaises(MissingDep):
+        from dvc.dependency.base import DependencyDoesNotExistError
+
+        with self.assertRaises(DependencyDoesNotExistError):
             self.dvc.run(
                 cmd="",
                 deps=["non-existing-dep"],