Added test on optional input in a scatter step

conformance_tests.yaml

@@ -1920,6 +1920,15 @@
   doc: Test optional integer workflow inputs (unspecified)
   tags: [ workflow, inline_javascript, expression_tool ]
 
+- tool: tests/optional-input-scatter.cwl
+  job: tests/scatter-job1.json
+  output:
+    out: ["foo one", "foo two", "foo three", "foo four"]
+  id: optional_input_scatter
+  doc: |
+    Test optional step input with single scatter parameter
+  tags: [ scatter, workflow ]
+
 - job: tests/io-int.json
   output: {"o": 10}
   tool: tests/io-int-default-wf.cwl

tests/optional-input-scatter.cwl

@@ -0,0 +1,40 @@
+#!/usr/bin/env cwl-runner
+cwlVersion: v1.3.0-dev1
+class: Workflow
+inputs:
+  inp: string[]
+outputs:
+  out:
+    type: string[]
+    outputSource: step1/echo_out
+
+requirements:
+  - class: ScatterFeatureRequirement
+
+steps:
+  step1:
+    in:
+      echo_in: inp
+    out: [echo_out]
+    scatter: echo_in
+    run:
+      class: CommandLineTool
+      inputs:
+        echo_in:
+          type: string
+          inputBinding: {}
+        input_2:
+          type: File?
+          inputBinding: {}
+      outputs:
+        echo_out:
+          type: string
+          outputBinding:
+            glob: "step1_out"
+            loadContents: true
+            outputEval: $(self[0].contents)
+      baseCommand: "echo"
+      arguments:
+        - "-n"
+        - "foo"
+      stdout: "step1_out"