Schema.prototype.jsonSchema(): convert Mongoose Schema to JSON schema

lib/helpers/createJSONSchemaTypeDefinition.js

@@ -0,0 +1,24 @@
+'use strict';
+
+/**
+ * Handles creating `{ type: 'object' }` vs `{ bsonType: 'object' }` vs `{ bsonType: ['object', 'null'] }`
+ *
+ * @param {String} type
+ * @param {String} bsonType
+ * @param {Boolean} useBsonType
+ * @param {Boolean} isRequired
+ */
+
+module.exports = function createJSONSchemaTypeArray(type, bsonType, useBsonType, isRequired) {
+  if (useBsonType) {
+    if (isRequired) {
+      return { bsonType };
+    }
+    return { bsonType: [bsonType, 'null'] };
+  } else {
+    if (isRequired) {
+      return { type };
+    }
+    return { type: [type, 'null'] };
+  }
+};

lib/schema.js

@@ -2886,6 +2886,92 @@ Schema.prototype._preCompile = function _preCompile() {
   this.plugin(idGetter, { deduplicate: true });
 };
 
+/**
+ * Returns a JSON schema representation of this Schema.
+ *
+ * By default, returns normal [JSON schema representation](https://json-schema.org/learn/getting-started-step-by-step), which is not typically what you want to use with
+ * [MongoDB's `$jsonSchema` collection option](https://www.mongodb.com/docs/manual/core/schema-validation/specify-json-schema/).
+ * Use the `useBsonType: true` option to return MongoDB `$jsonSchema` syntax instead.
+ *
+ * In addition to types, `jsonSchema()` supports the following Mongoose validators:
+ * - `enum` for strings and numbers
+ *
+ * #### Example:
+ *    const schema = new Schema({ name: String });
+ *    // { required: ['_id'], properties: { name: { type: ['string', 'null'] }, _id: { type: 'string' } } }
+ *    schema.toJSONSchema();
+ *
+ *    // { required: ['_id'], properties: { name: { bsonType: ['string', 'null'] }, _id: { bsonType: 'objectId' } } }
+ *    schema.toJSONSchema({ useBsonType: true });
+ *
+ * @param {Object} [options]
+ * @param [Boolean] [options.useBsonType=false] if true, specify each path's type using `bsonType` rather than `type` for MongoDB $jsonSchema support
+ */
+
+Schema.prototype.toJSONSchema = function toJSONSchema(options) {
+  const useBsonType = options?.useBsonType ?? false;
+  const result = useBsonType ? { required: [], properties: {} } : { type: 'object', required: [], properties: {} };
+  for (const path of Object.keys(this.paths)) {
+    const schemaType = this.paths[path];
+
+    // Skip Map embedded paths, maps will be handled seperately.
+    if (schemaType._presplitPath.indexOf('$*') !== -1) {
+      continue;
+    }
+
+    // Nested paths are stored as `nested.path` in the schema type, so create nested paths in the json schema
+    // when necessary.
+    const isNested = schemaType._presplitPath.length > 1;
+    let jsonSchemaForPath = result;
+    if (isNested) {
+      for (let i = 0; i < schemaType._presplitPath.length - 1; ++i) {
+        const subpath = schemaType._presplitPath[i];
+        if (jsonSchemaForPath.properties[subpath] == null) {
+          jsonSchemaForPath.properties[subpath] = useBsonType
+            ? {
+              bsonType: ['object', 'null'],
+              properties: {}
+            }
+            : {
+              type: ['object', 'null'],
+              properties: {}
+            };
+        }
+        jsonSchemaForPath = jsonSchemaForPath.properties[subpath];
+      }
+    }
+
+    const lastSubpath = schemaType._presplitPath[schemaType._presplitPath.length - 1];
+    let isRequired = false;
+    if (path === '_id') {
+      if (!jsonSchemaForPath.required) {
+        jsonSchemaForPath.required = [];
+      }
+      jsonSchemaForPath.required.push('_id');
+      isRequired = true;
+    } else if (schemaType.options.required && typeof schemaType.options.required !== 'function') {
+      if (!jsonSchemaForPath.required) {
+        jsonSchemaForPath.required = [];
+      }
+      // Only `required: true` paths are required, conditional required is not required
+      jsonSchemaForPath.required.push(lastSubpath);
+      isRequired = true;
+    }
+    jsonSchemaForPath.properties[lastSubpath] = schemaType.toJSONSchema(options);
+    if (schemaType.options.enum) {
+      jsonSchemaForPath.properties[lastSubpath].enum = isRequired
+        ? schemaType.options.enum
+        : [...schemaType.options.enum, null];
+    }
+  }
+
+  // Otherwise MongoDB errors with "$jsonSchema keyword 'required' cannot be an empty array"
+  if (result.required.length === 0) {
+    delete result.required;
+  }
+  return result;
+};
+
 /*!
  * Module exports.
  */

lib/schema/array.js

@@ -21,6 +21,7 @@ const isOperator = require('../helpers/query/isOperator');
 const util = require('util');
 const utils = require('../utils');
 const castToNumber = require('./operators/helpers').castToNumber;
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 const geospatial = require('./operators/geospatial');
 const getDiscriminatorByValue = require('../helpers/discriminator/getDiscriminatorByValue');
 
@@ -700,6 +701,23 @@ handle.$ne = SchemaArray.prototype._castForQuery;
 handle.$nin = SchemaType.prototype.$conditionalHandlers.$nin;
 handle.$in = SchemaType.prototype.$conditionalHandlers.$in;
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaArray.prototype.toJSONSchema = function toJSONSchema(options) {
+  const embeddedSchemaType = this.getEmbeddedSchemaType();
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return {
+    ...createJSONSchemaTypeDefinition('array', 'array', options?.useBsonType, isRequired),
+    items: embeddedSchemaType.toJSONSchema(options)
+  };
+};
+
 /*!
  * Module exports.
  */

lib/schema/bigint.js

@@ -7,6 +7,7 @@
 const CastError = require('../error/cast');
 const SchemaType = require('../schemaType');
 const castBigInt = require('../cast/bigint');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 
 /**
  * BigInt SchemaType constructor.
@@ -240,6 +241,19 @@ SchemaBigInt.prototype._castNullish = function _castNullish(v) {
   return v;
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaBigInt.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('string', 'long', options?.useBsonType, isRequired);
+};
+
 /*!
  * Module exports.
  */

lib/schema/boolean.js

@@ -7,6 +7,7 @@
 const CastError = require('../error/cast');
 const SchemaType = require('../schemaType');
 const castBoolean = require('../cast/boolean');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 
 /**
  * Boolean SchemaType constructor.
@@ -290,6 +291,19 @@ SchemaBoolean.prototype._castNullish = function _castNullish(v) {
   return v;
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaBoolean.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('boolean', 'bool', options?.useBsonType, isRequired);
+};
+
 /*!
  * Module exports.
  */

lib/schema/buffer.js

@@ -7,6 +7,7 @@
 const MongooseBuffer = require('../types/buffer');
 const SchemaBufferOptions = require('../options/schemaBufferOptions');
 const SchemaType = require('../schemaType');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 const handleBitwiseOperator = require('./operators/bitwise');
 const utils = require('../utils');
 
@@ -300,6 +301,19 @@ SchemaBuffer.prototype.castForQuery = function($conditional, val, context) {
   return casted ? casted.toObject({ transform: false, virtuals: false }) : casted;
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaBuffer.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('string', 'binData', options?.useBsonType, isRequired);
+};
+
 /*!
  * Module exports.
  */

lib/schema/date.js

@@ -8,6 +8,7 @@ const MongooseError = require('../error/index');
 const SchemaDateOptions = require('../options/schemaDateOptions');
 const SchemaType = require('../schemaType');
 const castDate = require('../cast/date');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 const getConstructorName = require('../helpers/getConstructorName');
 const utils = require('../utils');
 
@@ -426,6 +427,19 @@ SchemaDate.prototype.castForQuery = function($conditional, val, context) {
   return handler.call(this, val);
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaDate.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('string', 'date', options?.useBsonType, isRequired);
+};
+
 /*!
  * Module exports.
  */

lib/schema/decimal128.js

@@ -7,6 +7,7 @@
 const SchemaType = require('../schemaType');
 const CastError = SchemaType.CastError;
 const castDecimal128 = require('../cast/decimal128');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 const isBsonType = require('../helpers/isBsonType');
 
 /**
@@ -221,6 +222,19 @@ SchemaDecimal128.prototype.$conditionalHandlers = {
   $lte: handleSingle
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaDecimal128.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('string', 'decimal', options?.useBsonType, isRequired);
+};
+
 /*!
  * Module exports.
  */

lib/schema/documentArray.js

@@ -12,6 +12,7 @@ const SchemaDocumentArrayOptions =
   require('../options/schemaDocumentArrayOptions');
 const SchemaType = require('../schemaType');
 const cast = require('../cast');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 const discriminator = require('../helpers/model/discriminator');
 const handleIdOption = require('../helpers/schema/handleIdOption');
 const handleSpreadDoc = require('../helpers/document/handleSpreadDoc');
@@ -651,6 +652,23 @@ function cast$elemMatch(val, context) {
   return cast(schema, val, null, this && this.$$context);
 }
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaDocumentArray.prototype.toJSONSchema = function toJSONSchema(options) {
+  const itemsTypeDefinition = createJSONSchemaTypeDefinition('object', 'object', options?.useBsonType, false);
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return {
+    ...createJSONSchemaTypeDefinition('array', 'array', options?.useBsonType, isRequired),
+    items: { ...itemsTypeDefinition, ...this.schema.toJSONSchema(options) }
+  };
+};
+
 /*!
  * Module exports.
  */

lib/schema/double.js

@@ -7,6 +7,7 @@
 const CastError = require('../error/cast');
 const SchemaType = require('../schemaType');
 const castDouble = require('../cast/double');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 
 /**
  * Double SchemaType constructor.
@@ -204,6 +205,18 @@ SchemaDouble.prototype.$conditionalHandlers = {
   $lte: handleSingle
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaDouble.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('number', 'double', options?.useBsonType, isRequired);
+};
 
 /*!
  * Module exports.

lib/schema/int32.js

@@ -7,6 +7,7 @@
 const CastError = require('../error/cast');
 const SchemaType = require('../schemaType');
 const castInt32 = require('../cast/int32');
+const createJSONSchemaTypeDefinition = require('../helpers/createJSONSchemaTypeDefinition');
 const handleBitwiseOperator = require('./operators/bitwise');
 
 /**
@@ -246,6 +247,19 @@ SchemaInt32.prototype.castForQuery = function($conditional, val, context) {
   }
 };
 
+/**
+ * Returns this schema type's representation in a JSON schema.
+ *
+ * @param [options]
+ * @param [options.useBsonType=false] If true, return a representation with `bsonType` for use with MongoDB's `$jsonSchema`.
+ * @returns {Object} JSON schema properties
+ */
+
+SchemaInt32.prototype.toJSONSchema = function toJSONSchema(options) {
+  const isRequired = this.options.required && typeof this.options.required !== 'function';
+  return createJSONSchemaTypeDefinition('number', 'int', options?.useBsonType, isRequired);
+};
+
 
 /*!
  * Module exports.