better error message for wrong outputSource

cwltool/checker.py

@@ -389,6 +389,11 @@ def check_all_types(
                         )
             else:
                 parm_id = cast(str, sink[sourceField])
+                if parm_id not in src_dict:
+                    raise SourceLine(sink, sourceField, ValidationException).makeError(
+                        f"{sourceField} not found: {parm_id}"
+                    )
+
                 srcs_of_sink = [src_dict[parm_id]]
                 linkMerge = None
 

tests/checker_wf/broken-wf4.cwl

@@ -0,0 +1,20 @@
+#!/usr/bin/env cwl-runner
+class: Workflow
+cwlVersion: v1.0
+inputs:
+  letters0:
+    type: string
+    default: "a0"
+
+outputs:
+  all:
+    type: File
+    outputSource: echo_w
+
+steps:
+  echo_w:
+    run: echo.cwl
+    in:
+      echo_in: letters0
+    out: [txt]
+

tests/test_examples.py

@@ -1731,3 +1731,13 @@ def test_record_outputeval() -> None:
         == "sha1$da39a3ee5e6b4b0d3255bfef95601890afd80709"
     )
     assert result["annotation_gtf"]["size"] == 0
+
+
+def tests_outputsource_valid_identifier_invalid_source() -> None:
+    """Confirm error for invalid source that was also a valid identifier."""
+    tool_path = get_data("tests/checker_wf/broken-wf4.cwl")
+    err_code, stdout, stderr = get_main_output([tool_path])
+    assert err_code == 1
+    stderr = re.sub(r"\s\s+", " ", stderr)
+    assert "tests/checker_wf/broken-wf4.cwl:12:5: outputSource not found" in stderr
+    assert "tests/checker_wf/broken-wf4.cwl#echo_w" in stderr