fix: apply filters only to fieldmaps

CHANGES.rst

@@ -1,3 +1,23 @@
+2.15.2 (October 2, 2026)
+========================
+Patch release in the 2.15.x series.
+
+This includes two fixes for fieldmap-less estimation:
+
+- In multi-session datasets, a subject-level anatomical reference (i.e., without
+  a ``session`` entity) was not found for session-specific EPI data.
+  A session-matched anatomical image is still preferred when available.
+- ``bids_filters`` intended for fieldmaps (e.g., ``{"datatype": "fmap"}``) were also
+  applied when searching for the anatomical reference and EPI targets, silently
+  preventing fieldmap-less estimation (nipreps/fmriprep#3632).
+
+It also fixes the PEPOLAR heuristics ignoring ``acquisition`` filters, and
+finding no estimators when filtering on a single ``ceagent``.
+
+* FIX: Do not apply fieldmap filters to fieldmap-less queries (#563)
+* FIX: Allow sessionless anatomical references for fieldmap-less estimation (#562)
+
+
 2.15.1 (September 28, 2026)
 ===========================
 Patch release in the 2.15.x series.

sdcflows/utils/tests/test_wrangler.py

@@ -5,7 +5,7 @@
 import pytest
 from niworkflows.utils.testing import generate_bids_skeleton
 
-from sdcflows.fieldmaps import clear_registry, get_identifier
+from sdcflows.fieldmaps import EstimatorType, clear_registry, get_identifier
 from sdcflows.utils.wrangler import find_estimators
 
 
@@ -661,3 +661,64 @@ def test_fieldmapless(tmp_path):
     )
     clear_registry()
     rmtree(bids_dir)
+
+
+ANAT = (EstimatorType.ANAT, None)
+PEPOLAR_A = (EstimatorType.PEPOLAR, 'A')
+PEPOLAR_B = (EstimatorType.PEPOLAR, 'B')
+
+
+@pytest.mark.parametrize(
+    ('bids_filters', 'expected'),
+    [
+        (None, {ANAT, PEPOLAR_A, PEPOLAR_B}),
+        ({'datatype': 'fmap'}, {ANAT, PEPOLAR_A, PEPOLAR_B}),
+        ({'datatype': 'fmap', 'run': '9999'}, {ANAT}),
+        ({'acquisition': 'A'}, {ANAT, PEPOLAR_A}),
+        ({'ceagent': 'gad'}, {ANAT, PEPOLAR_A, PEPOLAR_B}),
+    ],
+    ids=['none', 'datatype', 'run', 'acquisition', 'ceagent'],
+)
+def test_filters(tmp_path, bids_filters, expected):
+    """Filters restrict fieldmaps, but not fieldmap-less anatomical references or targets."""
+    epi = {'suffix': 'epi', 'ce': 'gad', 'metadata': {'TotalReadoutTime': 0.05}}
+
+    spec = {
+        '01': {
+            'anat': [{'suffix': 'T1w'}],
+            'fmap': [
+                {
+                    **epi,
+                    'acq': acq,
+                    'dir': pedir,
+                    'metadata': {**epi['metadata'], 'PhaseEncodingDirection': pe},
+                }
+                for acq in ('A', 'B')
+                for pedir, pe in (('AP', 'j'), ('PA', 'j-'))
+            ],
+            'func': [
+                {
+                    'task': 'rest',
+                    'suffix': 'bold',
+                    'metadata': {
+                        'RepetitionTime': 0.8,
+                        'TotalReadoutTime': 0.5,
+                        'PhaseEncodingDirection': 'j',
+                    },
+                }
+            ],
+        },
+    }
+    bids_dir = tmp_path / 'bids'
+    generate_bids_skeleton(bids_dir, spec)
+    est = find_estimators(
+        layout=gen_layout(bids_dir),
+        subject='01',
+        fmapless=True,
+        force_fmapless=True,
+        bids_filters=bids_filters,
+    )
+    assert len(est) == len(expected)
+    # The first source is the T1w for ANAT, and an EPI fieldmap for PEPOLAR
+    assert {(e.method, e.sources[0].entities.get('acquisition')) for e in est} == expected
+    clear_registry()

sdcflows/utils/wrangler.py

@@ -107,7 +107,9 @@ def find_estimators(
         The logger used to relay messages. If not provided, one will be created.
     bids_filters
         Optional dictionary of key/values to filter the entities on.
-        This allows lower level file inclusion/exclusion.
+        This allows lower level file inclusion/exclusion of fieldmap files.
+        Except for ``session``, filters are not applied when querying the
+        anatomical reference and targets of fieldmap-less estimation.
     anat_suffix : :obj:`str` or :obj:`list`
         String or list of strings to filter anatomical images for fieldmap-less
         approaches. If not provided, ``T1w`` is used.
@@ -329,6 +331,7 @@ def find_estimators(
         'part': ['mag', None],
         'scope': 'raw',  # Ensure derivatives are not captured
     }
+    no_filter_entities = base_entities.copy()
 
     if bids_filters:
         filters = bids_filters.copy()  # copy to avoid altering in place
@@ -411,12 +414,16 @@ def find_estimators(
                 estimators.append(e)
 
         # A bunch of heuristics to select EPI fieldmaps
-        acqs = base_entities.get('acquisitions') or layout.get_acquisitions(
-            subject=subject, suffix='epi'
-        ) + [None]
-        contrasts = base_entities.get('ceagent') or layout.get_ceagents(
-            subject=subject, suffix='epi'
-        ) + [None]
+        acqs = (
+            listify(base_entities['acquisition'])
+            if 'acquisition' in base_entities
+            else layout.get_acquisitions(subject=subject, suffix='epi') + [None]
+        )
+        contrasts = (
+            listify(base_entities['ceagent'])
+            if 'ceagent' in base_entities
+            else layout.get_ceagents(subject=subject, suffix='epi') + [None]
+        )
         for ses, acq, ce in product(sessions, acqs, contrasts):
             entities = base_entities.copy()
             entities.update({'suffix': 'epi', 'session': ses, 'acquisition': acq, 'ceagent': ce})
@@ -513,12 +520,14 @@ def find_estimators(
         fmapless = False
 
     # Find fieldmap-less schemes
-    anat_file = layout.get(**{**base_entities, **{'suffix': anat_suffix, 'session': sessions}})
+    anat_file = layout.get(
+        **{**no_filter_entities, **{'suffix': anat_suffix, 'session': sessions}}
+    )
 
     # Fall back to a subject-level/sessionless anatomical reference.
     if not anat_file:
         anat_file = layout.get(
-            **{**base_entities, **{'suffix': anat_suffix, 'session': Query.NONE}}
+            **{**no_filter_entities, **{'suffix': anat_suffix, 'session': Query.NONE}}
         )
 
     if not fmapless or not anat_file:
@@ -531,7 +540,7 @@ def find_estimators(
         layout=layout,
         subject=subject,
         sessions=sessions,
-        base_entities=base_entities,
+        base_entities=no_filter_entities,
         suffixes=fmapless,
     )
     for spec in estimator_specs: