Update transformer types and documentation

Author: iby

README.md

@@ -45,34 +45,34 @@ You can use either a `postgres://` url connection string or the options to defin
 
 ```js
 const sql = postgres('postgres://username:password@host:port/database', {
-  host                 : '',            // Postgres ip address[s] or domain name[s]
-  port                 : 5432,          // Postgres server port[s]
-  path                 : '',            // unix socket path (usually '/tmp')
-  database             : '',            // Name of database to connect to
-  username             : '',            // Username of database user
-  password             : '',            // Password of database user
-  ssl                  : false,         // true, prefer, require, tls.connect options
-  max                  : 10,            // Max number of connections
-  idle_timeout         : 0,             // Idle connection timeout in seconds
-  connect_timeout      : 30,            // Connect timeout in seconds
-  no_prepare           : false,         // No automatic creation of prepared statements
-  types                : [],            // Array of custom types, see more below
-  onnotice             : fn,            // Defaults to console.log
-  onparameter          : fn,            // (key, value) when server param change
-  debug                : fn,            // Is called with (connection, query, params)
+  host                 : '',                   // Postgres ip address[s] or domain name[s]
+  port                 : 5432,                 // Postgres server port[s]
+  path                 : '',                   // unix socket path (usually '/tmp')
+  database             : '',                   // Name of database to connect to
+  username             : '',                   // Username of database user
+  password             : '',                   // Password of database user
+  ssl                  : false,                // true, prefer, require, tls.connect options
+  max                  : 10,                   // Max number of connections
+  idle_timeout         : 0,                    // Idle connection timeout in seconds
+  connect_timeout      : 30,                   // Connect timeout in seconds
+  no_prepare           : false,                // No automatic creation of prepared statements
+  types                : [],                   // Array of custom types, see more below
+  onnotice             : fn,                   // Defaults to console.log
+  onparameter          : fn,                   // (key, value) when server param change
+  debug                : fn,                   // Is called with (connection, query, params)
   transform            : {
-    column             : fn,            // Transforms incoming column names
-    value              : fn,            // Transforms incoming row values
-    row                : fn             // Transforms entire rows
+    column             : {to?: fn, from?: fn}, // Transforms incoming or outgoing column names
+    value              : {to?: fn, from?: fn}, // Transforms incoming or outgoing row values
+    row                : {to?: fn, from?: fn}, // Transforms entire incoming or outgoing rows
   },
   connection           : {
-    application_name   : 'postgres.js', // Default application_name
-    ...                                 // Other connection parameters
+    application_name   : 'postgres.js',        // Default application_name
+    ...                                        // Other connection parameters
   },
-  target_session_attrs : null,          // Use 'read-write' with multiple hosts to 
-                                        // ensure only connecting to primary
-  fetch_array_types    : true,          // Disable automatically fetching array types
-                                        // on initial connection.
+  target_session_attrs : null,                 // Use 'read-write' with multiple hosts to 
+                                               // ensure only connecting to primary
+  fetch_array_types    : true,                 // Disable automatically fetching array types
+                                               // on initial connection.
 })
 ```
 

types/index.d.ts

@@ -12,6 +12,10 @@ declare function postgres<T extends JSToPostgresTypeMap>(options?: postgres.Opti
  */
 declare function postgres<T extends JSToPostgresTypeMap>(url: string, options?: postgres.Options<T>): postgres.Sql<JSToPostgresTypeMap extends T ? {} : T>
 
+declare type ColumnTransformer = (column: string) => string;
+declare type ValueTransformer = (value: any) => any;
+declare type RowTransformer = (row: postgres.Row) => any;
+
 /**
  * Connection options of Postgres.
  */
@@ -52,12 +56,12 @@ interface BaseOptions<T extends JSToPostgresTypeMap> {
   debug: boolean | ((connection: number, query: string, parameters: any[]) => void);
   /** Transform hooks */
   transform: {
-    /** Transforms incoming column names */
-    column?: (column: string) => string;
-    /** Transforms incoming row values */
-    value?: (value: any) => any;
-    /** Transforms entire rows */
-    row?: (row: postgres.Row) => any;
+    /** Transforms incoming and outgoing column names. */
+    column?: (column: string) => string | { from?: (column: string) => string, to?: (column: string) => string };
+    /** Transforms incoming and outgoing row values. */
+    value?: (value: any) => any | { from?: (value: any) => any, to?: (value: any) => any };
+    /** Transforms entire incoming and outgoing rows. */
+    row?: (row: postgres.Row) => any | { from?: (row: postgres.Row) => any, to?: (row: postgres.Row) => any };
   };
   /** Connection parameters */
   connection: Partial<postgres.ConnectionParameters>;
@@ -109,21 +113,40 @@ declare namespace postgres {
   export const PostgresError: PostgresErrorType;
 
   /**
-   * Convert a string to Pascal case.
-   * @param str THe string to convert
-   * @returns The new string in Pascal case
+   * Convert a string from PascalCase to snake_case.
+   * @param str The PascalCase string to convert.
+   * @returns The new string in snake_case.
+   */
+  function fromPascal(str: string): string;
+  /**
+   * Convert a camelCase string to snake_case.
+   * @param str The camelCase string to convert.
+   * @returns The new string in snake_case.
+   */
+  function fromCamel(str: string): string;
+  /**
+   * Convert a kebab-case string to snake_case.
+   * @param str The kebab-case string to convert.
+   * @returns The new string in snake_case.
+   */
+  function fromKebab(str: string): string;
+
+  /**
+   * Convert a snake_case string to PascalCase.
+   * @param str The snake_case string to convert.
+   * @returns The new string in PascalCase.
    */
   function toPascal(str: string): string;
   /**
-   * Convert a string to Camel case.
-   * @param str THe string to convert
-   * @returns The new string in Camel case
+   * Convert a snake_case string to camelCase.
+   * @param str The snake_case string to convert.
+   * @returns The new string in camelCase.
    */
   function toCamel(str: string): string;
   /**
-   * Convert a string to Kebab case.
-   * @param str THe string to convert
-   * @returns The new string in Kebab case
+   * Convert a snake_case string to kebab-case.
+   * @param str The snake_case string to convert.
+   * @returns The new string in kebab-case.
    */
   function toKebab(str: string): string;