fix(policies): split comma-separated values on each merged input line

When a policy input declared as a comma-separated value in a workflow
contract was merged with a runtime value supplied via
--policy-input-from-file, getInputArguments split the merged string on
newlines first and returned the multi-line slice as-is, skipping the
per-value comma splitting. This collapsed the contract's comma-joined
segment into a single literal glob containing commas that matched
nothing.

Normalize consistently by splitting each line on commas as well, so a
comma-separated segment is always expanded into separate values
regardless of whether a runtime value was appended.

Assisted-by: Claude Code
Signed-off-by: Javier Rodriguez <javier@chainloop.dev>

Chainloop-Trace-Sessions: 20709f88-f555-488c-a8ae-e2d60903aff5, 7c9eb197-bbea-464f-9444-cd17ac09039c

Author: javirln

pkg/policies/policies.go

@@ -773,22 +773,19 @@ func getInputArguments(inputs map[string]string) map[string]any {
 	args := make(map[string]any)
 
 	for k, v := range inputs {
-		// scan for multiple values
+		// Normalize consistently: split on newlines first (multi-value inputs,
+		// e.g. a comma-separated contract value merged with runtime values by
+		// mergeRuntimeInputs), then split each line on commas. Doing both means a
+		// comma-separated segment is always expanded into separate values,
+		// regardless of whether it arrived as a single line or as one of several
+		// merged lines.
 		lines := strings.Split(strings.TrimRight(v, "\n"), "\n")
-		value := getValue(lines)
-
-		if value == nil {
-			continue
-		}
-		s, ok := value.(string)
-		if !ok {
-			// case for multivalued argument
-			args[k] = value
+		values := make([]string, 0, len(lines))
+		for _, line := range lines {
+			values = append(values, splitArgs(line)...)
 		}
 
-		// Single string, let's check for CSV and escaped commas `\,`
-		lines = splitArgs(s)
-		value = getValue(lines)
+		value := getValue(values)
 		if value == nil {
 			continue
 		}

pkg/policies/policies_test.go

@@ -799,6 +799,33 @@ func (s *testSuite) TestGetInputArguments() {
 			inputs:   map[string]string{"foo": "\n\n\nbar1\nbar2\n\nbar3\n"},
 			expected: map[string]any{"foo": []string{"bar1", "bar2", "bar3"}},
 		},
+		{
+			// A comma-separated contract value merged with runtime values (which
+			// mergeRuntimeInputs joins with newlines) must still split the
+			// comma-joined line into separate values instead of collapsing it into
+			// a single literal glob containing commas.
+			name:     "multiline input where a line is comma-separated",
+			inputs:   map[string]string{"foo": "**/vendor/**,**/redist/**\nC:/a\nC:/b"},
+			expected: map[string]any{"foo": []string{"**/vendor/**", "**/redist/**", "C:/a", "C:/b"}},
+		},
+		{
+			name:     "multiline input where several lines are comma-separated",
+			inputs:   map[string]string{"foo": "a,b\nc,d\ne"},
+			expected: map[string]any{"foo": []string{"a", "b", "c", "d", "e"}},
+		},
+		{
+			name:     "multiline input with escaped comma on a line",
+			inputs:   map[string]string{"foo": "a\\,b,c\nd"},
+			expected: map[string]any{"foo": []string{"a,b", "c", "d"}},
+		},
+		{
+			// A multiline input that reduces to a single non-empty value after
+			// blank-line filtering must return a plain string, not a one-element
+			// slice, so the two-stage split never over-wraps single values.
+			name:     "multiline input collapsing to a single value",
+			inputs:   map[string]string{"foo": "\nbar\n"},
+			expected: map[string]any{"foo": "bar"},
+		},
 		{
 			name:     "no input",
 			inputs:   nil,