Add test for optional numeric output returning 0

Author: bogdang989

conformance_tests.yaml

@@ -3304,3 +3304,12 @@
   tags: [ required, command_line_tool ]
   id: 252
 
+- tool: tests/optional-numerical-output-0.cwl
+  job: tests/empty.json
+  output:
+    {"out": 0}
+  label: optional_numerical_output_returns_0_not_null
+  doc: |
+    Test that optional number output is returned as 0, not null
+  tags: [ required, command_line_tool ]
+  id: 253

tests/optional-numerical-output-0.cwl

@@ -0,0 +1,16 @@
+cwlVersion: v1.0
+class: CommandLineTool
+baseCommand:
+  - echo
+  - "0"
+stdout: a.txt
+requirements:
+- class: InlineJavascriptRequirement
+inputs: []
+outputs:
+  out:
+    type: float?
+    outputBinding:
+      glob: "a.txt"
+      loadContents: true
+      outputEval: "${\n    return parseFloat(self[0].contents);\n}"