allow Object type coercion to Map

regression #538

WDL/Type.py

@@ -506,6 +506,12 @@ def coerces(self, rhs: Base, check_quant: bool = True) -> bool:
                 if not rhs_members[opt_k].optional:
                     return False
             return True
+        if isinstance(rhs, Map):
+            # Member names must coerce to the map key type, and each member type must coerce to the
+            # map value type.
+            return String().coerces(rhs.item_type[0]) and all(
+                vt.coerces(rhs.item_type[1]) for vt in self.members.values()
+            )
         if isinstance(rhs, Any):
             return self._check_optional(rhs, check_quant)
         return False

WDL/Value.py

@@ -507,11 +507,11 @@ def fail(msg):
         for k, v in self.value.items():
             if not (isinstance(v, Null) and value_type.optional):
                 map_key = None
+                map_value = None
                 try:
                     map_key = String(k).coerce(key_type)
                 except Error.RuntimeError:
                     fail(f"cannot coerce member name {k} to {key_type} map key")
-                map_value = None
                 if self.type.members[k].coerces(value_type):
                     with suppress(Error.RuntimeError):
                         map_value = v.coerce(value_type)
@@ -521,6 +521,7 @@ def fail(msg):
                         f" {self.type.members[k]} {k} to {value_type} map value"
                     )
                 entries.append((map_key, map_value))
+        assert self.type.coerces(desired_type)
         return Map(desired_type.item_type, entries)
 
     def __str__(self) -> Any:

tests/test_5stdlib.py

@@ -887,6 +887,24 @@ def test_issue524(self):
         }
         """, expected_exception=WDL.Error.EvalError)
 
+    def test_issue538(self):
+        # more struct init regression
+        self._test_task(R"""
+        version 1.0
+        struct StructWithMap { Map[String, String] map }
+        task RoundTripJson {
+            input {}
+            StructWithMap example = object {
+                map: { "foo":"bar", "fizz":"buzz" }
+            }
+            String dbg = read_string(write_json(example))
+            command {}
+            output {
+                StructWithMap result = read_json(write_json(example))
+            }
+        }
+        """)
+
     def test_bad_object(self):
         self._test_task(R"""
         version 1.0