Make comparisons in is_cached independent of order (#3731)

On is_cached, we used to compare two dicts: one of current stage in memory
created by `run` and one that's already written to the file.
As `outs` and `dicts` are lists (which is generate by `dumpd`), the
comparison was dependent on the order of outs and dicts.

So, the `run` before and now, can be in different order and would fail
the comparisons.

dvc/serialize.py

@@ -23,7 +23,7 @@
 
 def _get_outs(stage: "PipelineStage"):
     outs_bucket = {}
-    for o in stage.outs:
+    for o in sort_by_path(stage.outs):
         bucket_key = ["metrics"] if o.metric else ["outs"]
 
         if not o.metric and o.persist:
@@ -32,7 +32,7 @@ def _get_outs(stage: "PipelineStage"):
             bucket_key += ["no_cache"]
         key = "_".join(bucket_key)
         outs_bucket[key] = outs_bucket.get(key, []) + [o.def_path]
-    return [(key, outs_bucket[key]) for key in outs_bucket.keys()]
+    return [(key, outs_bucket[key]) for key in sorted(outs_bucket.keys())]
 
 
 def get_params_deps(stage: "PipelineStage"):
@@ -79,7 +79,7 @@ def to_pipeline_file(stage: "PipelineStage"):
     res = [
         (stage.PARAM_CMD, stage.cmd),
         (stage.PARAM_WDIR, stage.resolve_wdir()),
-        (stage.PARAM_DEPS, [d.def_path for d in deps]),
+        (stage.PARAM_DEPS, sorted([d.def_path for d in deps])),
         (stage.PARAM_PARAMS, serialized_params),
         *_get_outs(stage),
         (stage.PARAM_LOCKED, stage.locked),

dvc/stage/__init__.py

@@ -5,7 +5,7 @@
 import subprocess
 import threading
 
-from itertools import chain
+from itertools import chain, product
 
 from funcy import project
 
@@ -387,6 +387,15 @@ def is_cached(self):
             out.pop(LocalRemote.PARAM_CHECKSUM, None)
             out.pop(S3Remote.PARAM_CHECKSUM, None)
 
+        # outs and deps are lists of dicts. To check equality, we need to make
+        # them independent of the order, so, we convert them to dicts.
+        combination = product(
+            [old_d, new_d], [self.PARAM_DEPS, self.PARAM_OUTS]
+        )
+        for coll, key in combination:
+            if coll.get(key):
+                coll[key] = {item["path"]: item for item in coll[key]}
+
         if old_d != new_d:
             return False