Gates the failure cap on generation_guarantee, as its own docstring promised

Review on #7433 caught a contradiction I introduced: the field's docstring says it is meaningful
only together with generation_guarantee, but the loop check ran unconditionally. With the guarantee
off and a cap below generation_num_trials, a fixed-attempt run would have ended before delivering
the attempts it was asked for.

The guarantee is also the only mode that needs the cap. Without it the existing check already stops
on generation_num_trials attempts, so there is no unbounded run to bound and the cap has nothing to
add. Gating the condition makes the code match the contract rather than loosening the contract to
match the code.

The attempt-mode test was parametrised over caps of None and 100 against 10 requested attempts, so
it never exercised a cap that could fire; a cap of 3 is added, which is the case the reviewer
identified as uncovered.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JFz91VMgmrjS4XR6f9Q9Z2

Author: 2047767028-lang

source/isaaclab/isaaclab/envs/mimic_env_cfg.py

@@ -41,10 +41,13 @@ class DataGenConfig:
     max_num_failures: int | None = None
     """Maximum number of failed generation attempts before stopping, or None for no limit.
 
-    Only meaningful together with :attr:`generation_guarantee`. With the guarantee enabled,
-    generation keeps retrying until :attr:`generation_num_trials` demos succeed, so a task whose
-    success rate is low can run for an unbounded number of attempts; this caps that. Defaults to
-    None so the guarantee keeps its usual meaning unless a limit is asked for.
+    Only applies together with :attr:`generation_guarantee`. With the guarantee enabled, generation
+    keeps retrying until :attr:`generation_num_trials` demos succeed, so a task whose success rate is
+    low can run for an unbounded number of attempts; this caps that. Defaults to None so the
+    guarantee keeps its usual meaning unless a limit is asked for.
+
+    With the guarantee disabled, generation already stops after :attr:`generation_num_trials`
+    attempts and this field is ignored, so setting it cannot cut a fixed-attempt run short.
     """
 
     seed: int = 1

source/isaaclab_mimic/isaaclab_mimic/datagen/generation.py

@@ -141,9 +141,11 @@ def env_loop(
                     break
 
                 # with the success guarantee on, nothing else bounds the run: a task that rarely
-                # succeeds retries forever. max_num_failures is the opt-in bound on that.
+                # succeeds retries forever. max_num_failures is the opt-in bound on that. Without the
+                # guarantee the check above already stops on generation_num_trials attempts, so the
+                # cap has nothing to add and must not cut a fixed-attempt run short.
                 max_num_failures = env.cfg.datagen_config.max_num_failures
-                if max_num_failures is not None and num_failures >= max_num_failures:
+                if generation_guarantee and max_num_failures is not None and num_failures >= max_num_failures:
                     print(
                         f"Reached {num_failures} failures (max_num_failures={max_num_failures}) after"
                         f" {num_success}/{generation_num_trials} successes. Exiting."

source/isaaclab_mimic/test/test_generation_failure_cap.py

@@ -108,9 +108,13 @@ def test_cap_reached_before_enough_successes_ends_the_run():
     assert (succ, fail) == (2, 4)
 
 
-@pytest.mark.parametrize("max_num_failures", [None, 100])
+@pytest.mark.parametrize("max_num_failures", [None, 3, 100])
 def test_attempt_based_termination_is_unchanged(max_num_failures):
-    """With the guarantee off the run still stops on ``generation_num_trials`` attempts."""
+    """With the guarantee off the run stops on ``generation_num_trials`` attempts, cap or no cap.
+
+    A cap of 3 against 10 requested attempts is the case that matters: the fixed-attempt contract
+    says the run delivers the attempts it was asked for, so the cap must not end it at 3.
+    """
     how, _, _, attempts = _run(
         [False] * 100, max_num_failures=max_num_failures, generation_num_trials=10, generation_guarantee=False
     )