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 @@ from .exceptions import (
     StagePathNotDirectoryError,
     StageCommitError,
     StageUpdateError,
-    MissingDep,
     MissingDataSource,
 )
 from . import params
@@ -374,8 +373,7 @@ class Stage(params.StageParams):
 
         # 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 @@ class Stage(params.StageParams):
         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 @@ class Stage(params.StageParams):
         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 @@ class Stage(params.StageParams):
 
     @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 @@ class Stage(params.StageParams):
                     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 @@ class StageUpdateError(DvcException):
         )
 
 
-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 @@ from dvc.stage.exceptions import (
     StagePathOutsideError,
     StagePathNotFoundError,
     StagePathNotDirectoryError,
-    MissingDep,
 )
 from dvc.system import System
 from dvc.utils import file_md5
@@ -79,7 +78,9 @@ class TestRunEmpty(TestDvc):
 
 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"],