#lang racket/base
(require (for-syntax racket/base)
racket/runtime-path
racket/promise)
(provide lazy-require)
(define-syntax (lazy-require stx)
(syntax-case stx ()
[(lazy-require [modpath (thing ...)] ...)
#`(begin (define-namespace-anchor anchor)
(lazy-require1 modpath (thing ...) anchor #,stx)
...)]))
(define-syntax (lazy-require1 stx)
(syntax-case stx ()
[(lazy-require1 modpath (name ...) anchor orig-stx)
(with-syntax ([(defn ...)
(for/list ([name (in-list (syntax->list #'(name ...)))])
(unless (identifier? name)
(raise-syntax-error #f "expected identifier" #'orig-stx name))
(with-syntax ([name name]
[(aux) (generate-temporaries (list name))])
#`(begin (define aux (make-lazy-function 'name get-sym))
(define-syntax name
(make-rename-transformer
(syntax-property (quote-syntax aux)
'not-provide-all-defined #t))))))])
#'(begin (define-runtime-module-path-index mpi-var (quasiquote modpath))
(define (get-sym sym)
(parameterize ((current-namespace (namespace-anchor->namespace anchor)))
(dynamic-require mpi-var sym)))
defn ...))]))
(define (make-lazy-function name get-sym)
(let ([fun-p (delay/sync (get-sym name))])
(procedure-rename
(make-keyword-procedure
(lambda (kws kwargs . args)
(keyword-apply (force fun-p) kws kwargs args)))
name)))