feat(grpc): generate an example message from the method schema (#613)

2026-09-10 03:41:52 +02:00 · 2026-08-31 10:44:31 -07:00
parent f18f93d613
commit fce1039bac
4 changed files with 553 additions and 64 deletions
@@ -0,0 +1,121 @@
+/**
+ * Subset of JSON Schema emitted by the gRPC reflection layer for a method's
+ * input message. See `message_to_json_schema` in the `yaak-grpc` crate.
+ */
+export type JsonSchema = {
+  type?: string;
+  format?: string;
+  properties?: Record<string, JsonSchema>;
+  items?: JsonSchema;
+  additionalProperties?: JsonSchema;
+  enum?: unknown[];
+  $defs?: Record<string, JsonSchema>;
+  $ref?: string;
+};
+
+const DEFS_PREFIX = "#/$defs/";
+const ROOT_REF = "#";
+
+// Protobuf 64-bit integers are encoded as strings in the JSON mapping
+const STRING_NUMBER_FORMATS = ["int64", "uint64", "sint64", "fixed64", "sfixed64"];
+
+// Refs on sibling branches each expand their own subtree, so a schema that references the
+// same messages repeatedly can produce exponentially many nodes without ever cycling.
+const MAX_NODES = 5000;
+
+type Budget = { remaining: number };
+
+/** Build a sample message with placeholder values for every field in the schema */
+export function buildExampleFromSchema(schema: JsonSchema): unknown {
+  // The root is already being built, so a `#` ref anywhere below it is a cycle
+  return buildValue(schema, schema, new Set([ROOT_REF]), { remaining: MAX_NODES });
+}
+
+function buildValue(
+  schema: JsonSchema,
+  root: JsonSchema,
+  refPath: Set<string>,
+  budget: Budget,
+): unknown {
+  if (schema == null || typeof schema !== "object" || budget.remaining <= 0) {
+    return null;
+  }
+
+  budget.remaining -= 1;
+
+  if (typeof schema.$ref === "string") {
+    if (refPath.has(schema.$ref)) {
+      return {};
+    }
+    const resolved = resolveRef(schema.$ref, root);
+    if (resolved == null) {
+      return {};
+    }
+    return buildValue(resolved, root, new Set(refPath).add(schema.$ref), budget);
+  }
+
+  if (Array.isArray(schema.enum)) {
+    return schema.enum[0] ?? "";
+  }
+
+  switch (schema.type) {
+    case "object":
+      return buildObject(schema, root, refPath, budget);
+    case "array":
+      return schema.items == null ? [] : [buildValue(schema.items, root, refPath, budget)];
+    case "string":
+      return buildString(schema.format);
+    case "number":
+      return 0;
+    case "boolean":
+      return false;
+    default:
+      return null;
+  }
+}
+
+function buildObject(
+  schema: JsonSchema,
+  root: JsonSchema,
+  refPath: Set<string>,
+  budget: Budget,
+): unknown {
+  if (schema.properties != null && typeof schema.properties === "object") {
+    const example: Record<string, unknown> = {};
+    for (const [name, propertySchema] of Object.entries(schema.properties)) {
+      example[name] = buildValue(propertySchema, root, refPath, budget);
+    }
+    return example;
+  }
+
+  // Maps have no properties, only a value schema
+  if (schema.additionalProperties != null) {
+    return { key: buildValue(schema.additionalProperties, root, refPath, budget) };
+  }
+
+  return {};
+}
+
+function buildString(format: string | undefined): string {
+  if (format === "date-time") {
+    return new Date().toISOString();
+  }
+  // Duration JSON is a decimal string with an `s` suffix, and an empty one fails to parse
+  if (format === "duration") {
+    return "0s";
+  }
+  if (format != null && STRING_NUMBER_FORMATS.includes(format)) {
+    return "0";
+  }
+  return "";
+}
+
+function resolveRef(ref: string, root: JsonSchema): JsonSchema | null {
+  if (ref === ROOT_REF) {
+    return root;
+  }
+  if (!ref.startsWith(DEFS_PREFIX)) {
+    return null;
+  }
+  return root.$defs?.[ref.slice(DEFS_PREFIX.length)] ?? null;
+}