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TypeScript

/**
* 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;
}