Handle non-Job objects in Job equality check.

changelog.txt

@@ -18,7 +18,7 @@ Added
 Changed
 +++++++
 
- - Optimized job hash and equality checks (#442).
+ - Optimized job hash and equality checks (#442, #455).
  - Optimized ``H5Store`` initialization (#443).
  - State points are loaded lazily when ``Job`` is opened by id (#238, #239).
 

signac/contrib/job.py

@@ -151,9 +151,11 @@ def __hash__(self):
         return hash(self.id)
 
     def __eq__(self, other):
-        return (self.id == other.id) and (
-            os.path.realpath(self._wd) == os.path.realpath(other._wd)
-        )
+        if not isinstance(other, type(self)):
+            return NotImplemented
+        return self.id == other.id and os.path.realpath(
+            self.workspace()
+        ) == os.path.realpath(other.workspace())
 
     def __str__(self):
         """Return the job's id."""

tests/test_job.py

@@ -131,6 +131,39 @@ def test_str(self):
         job = self.project.open_job({"a": 0})
         assert str(job) == job.id
 
+    def test_eq(self):
+        job = self.project.open_job({"a": 0})
+
+        # Make sure that Jobs can only be equal to other Job instances.
+        class NonJob:
+            """Minimal class that cannot be compared with Job objects."""
+
+            def __init__(self, job):
+                self.id = job.id
+                self._workspace = job.workspace()
+
+        class JobSubclass(Job):
+            """Minimal subclass that can be compared with Job objects."""
+
+            def __init__(self, job):
+                self._id = job.id
+                self._workspace = job.workspace()
+
+            def workspace(self):
+                return self._workspace
+
+        non_job = NonJob(job)
+        assert job != non_job
+        assert non_job != job
+
+        sub_job = JobSubclass(job)
+        assert job == sub_job
+        assert sub_job == job
+
+        job2 = self.project.open_job({"a": 0})
+        assert job == job2
+        assert job2 == job
+
     def test_isfile(self):
         job = self.project.open_job({"a": 0})
         fn = "test.txt"