model: make model entities frozen

we do not really need them to be mutable, plus we gain their instances now
being hashable, so we can add them in set() for example.

swh/model/hypothesis_strategies.py

@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import attr
 import datetime
 
 from hypothesis.strategies import (
@@ -94,9 +95,10 @@ def releases(draw):
         author=none(),
         date=none(),
         target=sha1_git()))
-    rel.date = date
-    rel.author = author
-    return rel
+    return attr.evolve(
+        rel,
+        date=date,
+        author=author)
 
 
 def revision_metadata():

swh/model/model.py

@@ -51,7 +51,7 @@ class BaseModel:
         return cls(**d)
 
 
-@attr.s
+@attr.s(frozen=True)
 class Person(BaseModel):
     """Represents the author/committer of a revision or release."""
     name = attr.ib(type=bytes)
@@ -59,7 +59,7 @@ class Person(BaseModel):
     fullname = attr.ib(type=bytes)
 
 
-@attr.s
+@attr.s(frozen=True)
 class Timestamp(BaseModel):
     """Represents a naive timestamp from a VCS."""
     seconds = attr.ib(type=int)
@@ -78,7 +78,7 @@ class Timestamp(BaseModel):
             raise ValueError('Microseconds must be in [0, 1000000[.')
 
 
-@attr.s
+@attr.s(frozen=True)
 class TimestampWithTimezone(BaseModel):
     """Represents a TZ-aware timestamp from a VCS."""
     timestamp = attr.ib(type=Timestamp)
@@ -105,7 +105,7 @@ class TimestampWithTimezone(BaseModel):
             negative_utc=d['negative_utc'])
 
 
-@attr.s
+@attr.s(frozen=True)
 class Origin(BaseModel):
     """Represents a software source: a VCS and an URL."""
     url = attr.ib(type=str)
@@ -117,7 +117,7 @@ class Origin(BaseModel):
         return r
 
 
-@attr.s
+@attr.s(frozen=True)
 class OriginVisit(BaseModel):
     """Represents a visit of an origin at a given point in time, by a
     SWH loader."""
@@ -176,7 +176,7 @@ class ObjectType(Enum):
     SNAPSHOT = 'snapshot'
 
 
-@attr.s
+@attr.s(frozen=True)
 class SnapshotBranch(BaseModel):
     """Represents one of the branches of a snapshot."""
     target = attr.ib(type=bytes)
@@ -198,7 +198,7 @@ class SnapshotBranch(BaseModel):
             target_type=TargetType(d['target_type']))
 
 
-@attr.s
+@attr.s(frozen=True)
 class Snapshot(BaseModel):
     """Represents the full state of an origin at a given point in time."""
     id = attr.ib(type=Sha1Git)
@@ -214,7 +214,7 @@ class Snapshot(BaseModel):
             })
 
 
-@attr.s
+@attr.s(frozen=True)
 class Release(BaseModel):
     id = attr.ib(type=Sha1Git)
     name = attr.ib(type=bytes)
@@ -261,7 +261,7 @@ class RevisionType(Enum):
     MERCURIAL = 'hg'
 
 
-@attr.s
+@attr.s(frozen=True)
 class Revision(BaseModel):
     id = attr.ib(type=Sha1Git)
     message = attr.ib(type=bytes)
@@ -291,7 +291,7 @@ class Revision(BaseModel):
             **d)
 
 
-@attr.s
+@attr.s(frozen=True)
 class DirectoryEntry(BaseModel):
     name = attr.ib(type=bytes)
     type = attr.ib(type=str,
@@ -301,7 +301,7 @@ class DirectoryEntry(BaseModel):
     """Usually one of the values of `swh.model.from_disk.DentryPerms`."""
 
 
-@attr.s
+@attr.s(frozen=True)
 class Directory(BaseModel):
     id = attr.ib(type=Sha1Git)
     entries = attr.ib(type=List[DirectoryEntry])
@@ -314,7 +314,7 @@ class Directory(BaseModel):
                      for entry in d['entries']])
 
 
-@attr.s
+@attr.s(frozen=True)
 class Content(BaseModel):
     sha1 = attr.ib(type=bytes)
     sha1_git = attr.ib(type=Sha1Git)

swh/model/tests/test_model.py

@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import attr
 import copy
 
 from hypothesis import given
@@ -44,8 +45,9 @@ def test_todict_origin_visits(origin_visit):
     obj = origin_visit.to_dict()
 
     assert 'type' not in obj['origin']
-    origin_visit.origin.type = None
-    assert origin_visit == type(origin_visit).from_dict(obj)
+    origin2 = attr.evolve(origin_visit.origin, type=None)
+    origin_visit2 = attr.evolve(origin_visit, origin=origin2)
+    assert origin_visit2 == type(origin_visit).from_dict(obj)
 
 
 def test_content_get_hash():