feat(schema-writer): add record support

src/schema-writer/field-emitter.ts

@@ -11,17 +11,18 @@ const SUPPORTED_TYPES = new Set([
   "array",
   "tuple",
   "object",
+  "record",
 ]);
 
 /**
  * Emits a Zod v4 expression string for a single FieldDescriptor.
- * Throws on unsupported types (union, record).
+ * Throws on unsupported types (union).
  */
 export function emitField(field: FieldDescriptor): string {
   if (!SUPPORTED_TYPES.has(field.type)) {
     throw new Error(
       `Unsupported field type "${field.type}" for field "${field.name}". ` +
-        "Only string, number, boolean, date, enum, array, tuple, and object are supported.",
+        "Only string, number, boolean, date, enum, array, tuple, object, and record are supported.",
     );
   }
 
@@ -60,6 +61,8 @@ function emitBaseExpression(field: FieldDescriptor): string {
       return emitTuple(field);
     case "object":
       return emitObject(field);
+    case "record":
+      return emitRecord(field);
     default:
       throw new Error(`Unexpected field type: ${field.type}`);
   }
@@ -187,3 +190,14 @@ function emitObject(field: FieldDescriptor): string {
   });
   return `z.object({ ${entries.join(", ")} })`;
 }
+
+function emitRecord(field: FieldDescriptor): string {
+  if (field.metadata.kind !== "record") {
+    throw new Error(
+      `Field "${field.name}" has type "record" but metadata kind is "${field.metadata.kind}"`,
+    );
+  }
+
+  const valueExpr = emitField(field.metadata.valueDescriptor);
+  return `z.record(z.string(), ${valueExpr})`;
+}

test/schema-writer/field-emitter.test.ts

@@ -312,6 +312,68 @@ describe("emitField", () => {
     });
   });
 
+  describe("record fields", () => {
+    it("emits z.record() with scalar value", () => {
+      const field = makeField({
+        type: "record",
+        metadata: {
+          kind: "record",
+          valueDescriptor: makeField({
+            name: "value",
+            type: "number",
+            metadata: { kind: "number" },
+          }),
+        },
+      });
+      expect(emitField(field)).toBe("z.record(z.string(), z.number())");
+    });
+
+    it("emits z.record() with enum value", () => {
+      const field = makeField({
+        type: "record",
+        metadata: {
+          kind: "record",
+          valueDescriptor: makeField({
+            name: "value",
+            type: "enum",
+            metadata: { kind: "enum", values: ["low", "medium", "high"] },
+          }),
+        },
+      });
+      expect(emitField(field)).toBe(
+        'z.record(z.string(), z.enum(["low", "medium", "high"]))',
+      );
+    });
+
+    it("emits optional record", () => {
+      const field = makeField({
+        type: "record",
+        isOptional: true,
+        metadata: {
+          kind: "record",
+          valueDescriptor: makeField({
+            name: "value",
+            type: "string",
+            metadata: { kind: "string" },
+          }),
+        },
+      });
+      expect(emitField(field)).toBe(
+        "z.record(z.string(), z.string()).optional()",
+      );
+    });
+
+    it("throws when metadata kind does not match record type", () => {
+      const field = makeField({
+        type: "record",
+        metadata: { kind: "string" },
+      });
+      expect(() => emitField(field)).toThrow(
+        'Field "test" has type "record" but metadata kind is "string"',
+      );
+    });
+  });
+
   describe("optional and nullable wrapping", () => {
     it("wraps with .optional()", () => {
       const field = makeField({
@@ -562,15 +624,14 @@ describe("emitField", () => {
       expect(() => emitField(field)).toThrow('Unsupported field type "union"');
     });
 
-    it("throws on record type", () => {
+    it("throws on record type with mismatched metadata", () => {
       const field = makeField({
         type: "record",
-        metadata: {
-          kind: "record",
-          valueDescriptor: makeField({ name: "value" }),
-        },
+        metadata: { kind: "string" },
       });
-      expect(() => emitField(field)).toThrow('Unsupported field type "record"');
+      expect(() => emitField(field)).toThrow(
+        'Field "test" has type "record" but metadata kind is "string"',
+      );
     });
   });
 });

test/schema-writer/round-trip.test.ts

@@ -343,6 +343,25 @@ describe("round-trip: schema -> introspect -> writeSchema -> eval -> introspect"
     }
   });
 
+  it("round-trips a record of numbers", () => {
+    const schema = z.object({
+      scores: z.record(z.string(), z.number()),
+    });
+    const { descriptor1, descriptor2 } = roundTrip(schema);
+
+    expect(descriptor2.fields[0].type).toBe("record");
+    expect(descriptor2.fields[0].name).toBe(descriptor1.fields[0].name);
+    expect(descriptor2.fields[0].metadata.kind).toBe("record");
+    if (
+      descriptor2.fields[0].metadata.kind === "record" &&
+      descriptor1.fields[0].metadata.kind === "record"
+    ) {
+      expect(descriptor2.fields[0].metadata.valueDescriptor.type).toBe(
+        descriptor1.fields[0].metadata.valueDescriptor.type,
+      );
+    }
+  });
+
   it("round-trips a complex multi-field schema", () => {
     const schema = z.object({
       name: z.string().min(1),

test/schema-writer/writer.test.ts

@@ -127,6 +127,27 @@ describe("writeSchema", () => {
         "export type Contact = z.infer<typeof contactSchema>;",
       );
     });
+
+    it("emits record type through writer", () => {
+      const form = makeForm({
+        fields: [
+          makeField({
+            name: "scores",
+            type: "record",
+            metadata: {
+              kind: "record",
+              valueDescriptor: makeField({
+                name: "value",
+                type: "number",
+                metadata: { kind: "number" },
+              }),
+            },
+          }),
+        ],
+      });
+      const result = writeSchema({ form });
+      expect(result.code).toContain("scores: z.record(z.string(), z.number())");
+    });
   });
 
   describe("tuple fields", () => {
@@ -209,22 +230,25 @@ describe("writeSchema", () => {
       );
     });
 
-    it("throws on unsupported record type", () => {
+    it("emits record type through writer", () => {
       const form = makeForm({
         fields: [
           makeField({
-            name: "map",
+            name: "scores",
             type: "record",
             metadata: {
               kind: "record",
-              valueDescriptor: makeField({ name: "value" }),
+              valueDescriptor: makeField({
+                name: "value",
+                type: "number",
+                metadata: { kind: "number" },
+              }),
             },
           }),
         ],
       });
-      expect(() => writeSchema({ form })).toThrow(
-        'Unsupported field type "record"',
-      );
+      const result = writeSchema({ form });
+      expect(result.code).toContain("scores: z.record(z.string(), z.number())");
     });
   });