run: introduce --always-changed

dvc/command/run.py

@@ -51,6 +51,7 @@ def run(self):
                 no_commit=self.args.no_commit,
                 outs_persist=self.args.outs_persist,
                 outs_persist_no_cache=self.args.outs_persist_no_cache,
+                always_changed=self.args.always_changed,
             )
         except DvcException:
             logger.exception("failed to run command")
@@ -189,6 +190,12 @@ def add_parser(subparsers, parent_parser):
         help="Declare output file or directory that will not be "
         "removed upon repro (do not put into DVC cache).",
     )
+    run_parser.add_argument(
+        "--always-changed",
+        action="store_true",
+        default=False,
+        help="Always consider this DVC-file as changed.",
+    )
     run_parser.add_argument(
         "command", nargs=argparse.REMAINDER, help="Command to execute."
     )

dvc/stage.py

@@ -139,6 +139,7 @@ class Stage(object):
     PARAM_OUTS = "outs"
     PARAM_LOCKED = "locked"
     PARAM_META = "meta"
+    PARAM_ALWAYS_CHANGED = "always_changed"
 
     SCHEMA = {
         Optional(PARAM_MD5): Or(str, None),
@@ -148,6 +149,7 @@ class Stage(object):
         Optional(PARAM_OUTS): Or(And(list, Schema([output.SCHEMA])), None),
         Optional(PARAM_LOCKED): bool,
         Optional(PARAM_META): object,
+        Optional(PARAM_ALWAYS_CHANGED): bool,
     }
 
     TAG_REGEX = r"^(?P<path>.*)@(?P<tag>[^\\/@:]*)$"
@@ -164,6 +166,7 @@ def __init__(
         locked=False,
         tag=None,
         state=None,
+        always_changed=False,
     ):
         if deps is None:
             deps = []
@@ -179,6 +182,7 @@ def __init__(
         self.md5 = md5
         self.locked = locked
         self.tag = tag
+        self.always_changed = always_changed
         self._state = state or {}
 
     def __repr__(self):
@@ -244,6 +248,9 @@ def _changed_deps(self):
             )
             return True
 
+        if self.always_changed:
+            return True
+
         for dep in self.deps:
             status = dep.status()
             if status:
@@ -457,6 +464,7 @@ def create(repo, **kwargs):
             wdir=wdir,
             cmd=kwargs.get("cmd", None),
             locked=kwargs.get("locked", False),
+            always_changed=kwargs.get("always_changed", False),
         )
 
         Stage._fill_stage_outputs(stage, **kwargs)
@@ -515,6 +523,7 @@ def create(repo, **kwargs):
                 not ignore_build_cache
                 and stage.is_cached
                 and not stage.is_callback
+                and not stage.always_changed
             ):
                 logger.info("Stage is cached, skipping.")
                 return None
@@ -619,6 +628,7 @@ def load(repo, fname):
             md5=d.get(Stage.PARAM_MD5),
             locked=d.get(Stage.PARAM_LOCKED, False),
             tag=tag,
+            always_changed=d.get(Stage.PARAM_ALWAYS_CHANGED, False),
             state=state,
         )
 
@@ -639,6 +649,7 @@ def dumpd(self):
                 Stage.PARAM_DEPS: [d.dumpd() for d in self.deps],
                 Stage.PARAM_OUTS: [o.dumpd() for o in self.outs],
                 Stage.PARAM_META: self._state.get("meta"),
+                Stage.PARAM_ALWAYS_CHANGED: self.always_changed,
             }.items()
             if value
         }
@@ -839,6 +850,7 @@ def run(self, dry=False, no_commit=False, force=False):
                 if (
                     not force
                     and not self.is_callback
+                    and not self.always_changed
                     and self._already_cached()
                 ):
                     self.checkout()
@@ -885,7 +897,7 @@ def status(self):
         if self.changed_md5():
             ret.append("changed checksum")
 
-        if self.is_callback:
+        if self.is_callback or self.always_changed:
             ret.append("always changed")
 
         if ret:

tests/unit/command/test_run.py

@@ -32,6 +32,7 @@ def test_run(mocker, dvc_repo):
             "outs-persist",
             "--outs-persist-no-cache",
             "outs-persist-no-cache",
+            "--always-changed",
             "command",
         ]
     )
@@ -58,6 +59,7 @@ def test_run(mocker, dvc_repo):
         ignore_build_cache=True,
         remove_outs=True,
         no_commit=True,
+        always_changed=True,
         cmd="command",
     )
 
@@ -83,6 +85,7 @@ def test_run_args_from_cli(mocker, dvc_repo):
         ignore_build_cache=False,
         remove_outs=False,
         no_commit=False,
+        always_changed=False,
         cmd="echo foo",
     )
 
@@ -108,5 +111,6 @@ def test_run_args_with_spaces(mocker, dvc_repo):
         ignore_build_cache=False,
         remove_outs=False,
         no_commit=False,
+        always_changed=False,
         cmd='echo "foo bar"',
     )

tests/unit/test_stage.py

@@ -107,3 +107,10 @@ def test_stage_run_ignore_sigint(mocker):
     assert communicate.called_once_with()
     signal_mock.assert_any_call(signal.SIGINT, signal.SIG_IGN)
     assert signal.getsignal(signal.SIGINT) == signal.default_int_handler
+
+
+def test_always_changed():
+    stage = Stage(None, "path", always_changed=True)
+    stage.save()
+    assert stage.changed()
+    assert stage.status()["path"] == ["always changed"]