Fix add_transformations broken state after invalid input (#5265)

* Fixes #2558
*  Added input validation in add_transformations to raise TypeError if any transformation is not callable, preventing broken trajectory state
*   Added test test_add_transformations_rejects_non_callable in testsuite/MDAnalysisTests/coordinates/base.py
* Add Harshit Gajjela to AUTHORS and update CHANGELOG

Author: harshitgajjela-droid

package/AUTHORS

@@ -272,6 +272,7 @@ Chronological list of authors
   - Khushi Phougat
   - Kushagar Garg
   - Jeremy M. G. Leung
+  - Harshit Gajjela
 
 External code
 -------------

package/CHANGELOG

@@ -15,11 +15,14 @@ The rules for this file:
 
 -------------------------------------------------------------------------------
 ??/??/?? IAlibay, orbeckst, marinegor, tylerjereddy, ljwoods2, marinegor,
-         spyke7, talagayev, tanii1125, BradyAJohnston, hejamu, jeremyleung521
+         spyke7, talagayev, tanii1125, BradyAJohnston, hejamu, jeremyleung521,
+         harshitgajjela-droid
 
  * 2.11.0
 
 Fixes
+ * Fixed bug in add_transformations allowing non-callable transformations
+   (Issue #2558, PR #2558)
  * Drop/Replace lock file test in test_xdr (Issue #5236, PR #5237)
  * HydrogenBondAnalysis: Fixed `count_by_time()` when using `run(FrameIterator)` that
    results in `self.start` and `self.end` being None (Issue #5200, PR #5202)

package/MDAnalysis/coordinates/base.py

@@ -1424,8 +1424,19 @@ def add_transformations(self, *transformations):
         --------
         :mod:`MDAnalysis.transformations`
 
+        Raises
+        ------
+        TypeError
+            If any transformation is not callable
+
         """
 
+        for transform in transformations:
+            if not callable(transform):
+                raise TypeError(
+                    "All transformations must be callable; "
+                    f"got object of type {type(transform)}"
+                )
         try:
             self.transformations = transformations
         except ValueError:

testsuite/MDAnalysisTests/coordinates/base.py

@@ -290,6 +290,13 @@ def transformed(ref):
         )
         return transformed
 
+    def test_add_transformations_rejects_non_callable(self):
+        u = mda.Universe.empty(1, trajectory=True)
+        with pytest.raises(
+            TypeError, match="All transformations must be callable"
+        ):
+            u.trajectory.add_transformations([1, 2, 3])
+
     def test_n_atoms(self, ref, reader):
         assert_equal(reader.n_atoms, ref.n_atoms)