fix: ensure the ME pathway does not crash at workflow build-time

Author: oesteban

fmriprep/workflows/base.py

@@ -335,17 +335,23 @@ def init_single_subject_wf(subject_id):
             config.loggers.workflow.error(message)
             raise ValueError(message)
 
-        config.loggers.workflow.debug(
-            f"{len(fmap_estimators)} fieldmap estimators found: "
-            f"{[e.method for e in fmap_estimators]}"
-        )
-
-        if "fieldmaps" in config.workflow.ignore:
+        if (
+            "fieldmaps" in config.workflow.ignore
+            and [f for f in fmap_estimators
+                 if f.method != fm.EstimatorType.ANAT]
+        ):
+            config.loggers.workflow.info(
+                'Option "--ignore fieldmaps" was set, but either "--use-syn-sdc" '
+                'or "--force-syn" were given, so fieldmap-less estimation will be executed.'
+            )
             fmap_estimators = [f for f in fmap_estimators
                                if f.method == fm.EstimatorType.ANAT]
-            config.loggers.workflow.debug(
-                "Ignoring fieldmap scans, using anatomical estimators: "
-                f"{[e.method for e in fmap_estimators]}"
+
+        if fmap_estimators:
+            config.loggers.workflow.info(
+                "B0 field inhomogeneity map will be estimated with "
+                f" the following {len(fmap_estimators)} estimators: "
+                f"{[e.method for e in fmap_estimators]}."
             )
 
     # Append the functional section to the existing anatomical exerpt
@@ -426,6 +432,8 @@ def init_single_subject_wf(subject_id):
         config.loggers.workflow.info(f"""\
 Setting-up fieldmap "{estimator.bids_id}" ({estimator.method}) with \
 <{', '.join(s.path.name for s in estimator.sources)}>""")
+
+        # Mapped and phasediff can be connected internally by SDCFlows
         if estimator.method in (fm.EstimatorType.MAPPED, fm.EstimatorType.PHASEDIFF):
             continue
 

fmriprep/workflows/bold/base.py

@@ -252,15 +252,19 @@ def init_func_preproc_wf(bold_file, has_fieldmap=False):
             from sdcflows.fieldmaps import get_identifier
 
             # Fallback to IntendedFor
-            bold_rel = re.sub(
-                r"^sub-[a-zA-Z0-9]*/", "", str(Path(bold_file).relative_to(layout.root))
+            intended_rel = re.sub(
+                r"^sub-[a-zA-Z0-9]*/",
+                "",
+                str(Path(
+                    bold_file if not multiecho else bold_file[0]
+                ).relative_to(layout.root))
             )
-            estimator_key = get_identifier(bold_rel)
+            estimator_key = get_identifier(intended_rel)
 
         if not estimator_key:
             has_fieldmap = False
             config.loggers.workflow.critical(
-                f"None of the available B0 fieldmaps are associated to <{bold_rel}>"
+                f"None of the available B0 fieldmaps are associated to <{bold_file}>"
             )
         else:
             config.loggers.workflow.info(f"Found usable B0 fieldmap <{estimator_key}>")