Add regression test for #19245

lib/galaxy_test/api/test_workflows.py

@@ -2157,6 +2157,38 @@ def test_run_workflow_pick_value_bam_pja(self):
         assert dataset_details["metadata_bam_index"]
         assert dataset_details["file_ext"] == "bam"
 
+    def test_expression_tool_output_in_format_source(self):
+        with self.dataset_populator.test_history() as history_id:
+            self._run_workflow(
+                """class: GalaxyWorkflow
+inputs:
+  input:
+    type: data
+steps:
+  skip:
+    tool_id: cat_data_and_sleep
+    in:
+      input1: input
+    when: $(false)
+  pick_larger:
+    tool_id: expression_pick_larger_file
+    in:
+      input1: skip/out_file1
+      input2: input
+  format_source:
+    tool_id: cat_data_and_sleep
+    in:
+      input1: pick_larger/larger_file
+test_data:
+  input:
+    value: 1.fastqsanger.gz
+    type: File
+    file_type: fastqsanger.gz
+""",
+                history_id=history_id,
+            )
+            self.dataset_populator.wait_for_history(history_id=history_id, assert_ok=True)
+
     def test_run_workflow_simple_conditional_step(self):
         with self.dataset_populator.test_history() as history_id:
             summary = self._run_workflow(

test/functional/tools/expression_pick_larger_file.xml

@@ -20,7 +20,7 @@
         <param name="input2" type="data" optional="true" label="Second file" />
     </inputs>
     <outputs>
-        <output name="larger_file" type="data" from="output" />
+        <output name="larger_file" type="data" from="output" format_source="input1" />
     </outputs>
     <tests>
         <test>