Fix corner case of empty items array (#871)

src/utils.js

@@ -157,9 +157,12 @@ function computeDefaults(schema, parentDefaults, definitions = {}) {
           if (schema.minItems > defaultsLength) {
             const defaultEntries = defaults || [];
             // populate the array with the defaults
+            const fillerSchema = Array.isArray(schema.items)
+              ? schema.additionalItems
+              : schema.items;
             const fillerEntries = fill(
               new Array(schema.minItems - defaultsLength),
-              computeDefaults(schema.items, schema.items.defaults, definitions)
+              computeDefaults(fillerSchema, fillerSchema.defaults, definitions)
             );
             // then fill up the rest with either the item default or empty, up to minItems
 

test/utils_test.js

@@ -292,6 +292,26 @@ describe("utils", () => {
           foo: 42,
         });
       });
+
+      it("should fill array with additional items schema when items is empty", () => {
+        const schema = {
+          type: "object",
+          properties: {
+            array: {
+              type: "array",
+              minItems: 1,
+              additionalItems: {
+                type: "string",
+                default: "foo",
+              },
+              items: [],
+            },
+          },
+        };
+        expect(getDefaultFormState(schema, {})).eql({
+          array: ["foo"],
+        });
+      });
     });
   });