;; repl.scm - friendlier repl with line editing and signal handling
;; Copyright (c) 2012-2013 Alex Shinn. All rights reserved.
;; BSD-style license: http://synthcode.com/license.txt
;;> A user-friendly REPL with line editing and signal handling. The
;;> default REPL provided by chibi-scheme is very minimal, meant
;;> primarily to be small and work on any platform. This module
;;> provides an advanced REPL that handles vt100 line editing and
;;> signal handling, so that C-c will interrupt a computation and
;;> bring you back to the REPL prompt. To use this repl, run
;;> \command{chibi-scheme -R} from the command line or within Emacs.
(define (with-signal-handler sig handler thunk)
(let ((old-handler #f))
(dynamic-wind
(lambda () (set! old-handler (set-signal-action! sig handler)))
thunk
(lambda () (set-signal-action! sig old-handler)))))
(define (warn msg . args)
(let ((out (current-error-port)))
(display msg out)
(for-each (lambda (x) (write-char #\space out) (write x out)) args)
(newline out)))
(define (write-to-string x)
(call-with-output-string (lambda (out) (write x out))))
(define (complete-sexp? str)
(call-with-input-string str
(lambda (in)
(let lp () (if (not (eof-object? (read/ss in))) (lp))))))
(define (read-line/complete-sexp in)
(let lp ((res ""))
(let ((line (read-line in)))
(cond
((eof-object? line)
(if (equal? res "") line res))
(else
(let ((res (string-append res line "\n")))
(if (protect (exn (else #f)) (complete-sexp? res))
res
(lp res))))))))
(define (buffer-complete-sexp? buf)
(complete-sexp? (buffer->string buf)))
(define module? vector?)
(define (module-env mod) (vector-ref mod 1))
(define (all-exports env)
(let lp ((env env) (res '()))
(if (not env)
res
(lp (env-parent env) (append (env-exports env) res)))))
(define (string-common-prefix-length strings)
(if (null? strings)
0
(let lp ((len (string-length (car strings)))
(prev (car strings))
(ls (cdr strings)))
(if (or (null? ls) (zero? len))
len
(lp (min len (string-cursor->index prev (string-mismatch prev (car ls))))
(car ls)
(cdr ls))))))
(define (make-sexp-buffer-completer)
(buffer-make-completer
(lambda (buf word)
(let* ((len (string-length word))
(candidates
(filter
(lambda (w)
(and (>= (string-length w) len)
(equal? word (substring w 0 len))))
(map symbol->string
(map identifier->symbol
(all-exports (interaction-environment))))))
(prefix-len (string-common-prefix-length candidates)))
(if (> prefix-len len)
(list (substring (car candidates) 0 prefix-len))
(sort candidates))))))
(define (describe x . o)
(let ((out (if (pair? o) (car o) (current-output-port))))
(cond
((null? x)
(display "empty list\n" out))
((list? x)
(display "list of length " out) (write (length x) out) (newline out)
(let lp ((ls x) (i 0))
(cond
((pair? ls)
(display " " out) (write i out) (display ": " out)
(write/ss (car ls) out) (newline out)
(lp (cdr ls) (+ i 1))))))
((pair? x)
(display "pair with car " out) (write/ss (car x) out) (newline out)
(display "and cdr " out) (write/ss (cdr x) out) (newline out))
((vector? x)
(let ((len (vector-length x)))
(display "vector of length " out) (write len out) (newline out)
(let lp ((i 0))
(cond
((< i len)
(display " " out) (write i out) (display ": " out)
(write/ss (vector-ref x i) out) (newline out)
(lp (+ i 1)))))))
((boolean? x)
(display (if x "boolean true\n" "boolean false\n") out))
((char? x)
(let ((n (char->integer x)))
(display "character " out) (write x out)
(display ", code: " out) (write n out)
(display ", #x" out) (display (number->string n 16) out)
(display ", #o" out) (display (number->string n 8) out)
(newline out)))
((and (integer? x) (exact? x))
(display "exact integer " out) (write x out)
(display "\n #x" out) (display (number->string x 16) out)
(display "\n #o" out) (display (number->string x 8) out)
(display "\n #b" out) (display (number->string x 2) out)
(newline out))
(else
(write/ss x out) (newline out)))))
;;> Runs an interactive REPL. Repeatedly displays a prompt,
;;> then Reads an expression, Evaluates the expression, Prints
;;> the result then Loops. Terminates when the end of input is
;;> reached or the \scheme|{\exit}| command is given.
;;>
;;> Basic Emacs-style line editing with persistent history
;;> completion is provided. C-c can be used to interrupt the
;;> current computation and drop back to the prompt. The
;;> following keyword arguments customize the REPL:
;;>
;;> \itemlist[
;;> \item{\scheme{in:} - the input port (default \scheme{(current-input-port)})}
;;> \item{\scheme{out:} - the output port (default \scheme{(current-output-port)})}
;;> \item{\scheme{module:} - the initial module}
;;> \item{\scheme{environment:} - the initial environment (default \scheme{(interaction-environment)})}
;;> \item{\scheme{escape:} - the command escape character (default \scheme|{#\\}|)}
;;> \item{\scheme{make-prompt:} - a procedure taking one argument (the current module name as a list) and returning a string to be used as the prompt}
;;> \item{\scheme{history:} - the initial command history}
;;> \item{\scheme{history-file:} - the file to save history to (default ~/.chibi-repl-history)}
;;> ]
;;>
;;> The module: and environment: keyword arguments should not both be given.
;;>
;;> REPL commands in the style of \hyperlink["http://s48.org/"]{Scheme48}
;;> are available to control out-of-band properties. By default a
;;> command is written as an identifier beginning with an "@"
;;> character, but this can be customized with the \scheme{escape:}
;;> keyword. The following commands are available:
;;>
;;> \itemlist[
;;> \item{\scheme|{\import <import-spec>}| - import the \var{<import-spec>} in the \scheme{interaction-environment}, useful if the \scheme{import} binding is not available}
;;> \item{\scheme|{\import-only <import-spec>}| - replace the \scheme{interaction-environment} with the given \var{<import-spec>}}
;;> \item{\scheme|{\in [<module>]}| - switch to \var{<module>}, or the \scheme{interaction-environment} if \var{<module>} is not specified}
;;> \item{\scheme|{\meta <expr>}| - evaluate \var{<expr>} in the \scheme{(meta)} module}
;;> \item{\scheme|{\meta-module-is <module>}| - switch the meta module to \var{<module>}}
;;> \item{\scheme|{\exit}| - exit the REPL}
;;> ]
(define-record-type Repl
(make-repl
in out escape module env meta-env make-prompt history-file history raw?)
repl?
(in repl-in repl-in-set!)
(out repl-out repl-out-set!)
(escape repl-escape repl-escape-set!)
(module repl-module repl-module-set!)
(env repl-env repl-env-set!)
(meta-env repl-meta-env repl-meta-env-set!)
(make-prompt repl-make-prompt repl-make-prompt-set!)
(history-file repl-history-file repl-history-file-set!)
(history repl-history repl-history-set!)
(raw? repl-raw? repl-raw?-set!))
(define (repl/import-aux rp args meta continue only?)
(let* ((mod-name (cadr args))
(mod+imps (eval `(resolve-import ',mod-name) (repl-meta-env rp))))
(cond
((pair? mod+imps)
(protect
(exn
(else
(print-exception exn (current-error-port))
(warn "error loading module:" mod-name)
(continue rp)))
(let ((env (if only? (make-environment) (repl-env rp)))
(imp-env
(module-env
(eval `(load-module ',(car mod+imps)) (repl-meta-env rp)))))
(%import env imp-env (cdr mod+imps) #f)
(repl-env-set! rp env)
(continue rp))))
(else
(warn "couldn't find module:" mod-name)
(continue rp)))))
(define (repl/import rp args meta continue)
(repl/import-aux rp args meta continue #f))
(define (repl/import-only rp args meta continue)
(repl/import-aux rp args meta continue #t))
(define (repl/in rp args meta continue)
(cond
((null? (cdr args))
(repl-module-set! rp #f)
(repl-env-set! rp (interaction-environment)))
((eval `(load-module ',(cadr args)) (repl-meta-env rp))
=> (lambda (m)
(repl-module-set! rp (cadr args))
(repl-env-set! rp (module-env m))))
(else
(warn "couldn't find module:" (cadr args))))
(continue rp))
(define (repl/meta rp args meta continue)
(cond
((null? (cdr args))
(warn "usage: @meta <expr>")
(continue rp))
((and (symbol? (cadr args))
(eqv? (repl-escape rp) (string-ref (symbol->string (cadr args)) 0)))
(meta rp (cdr args) (lambda _ (continue rp))))
(else
(eval (cadr args) (repl-meta-env rp))
(continue rp))))
(define (repl/meta-module-is rp args meta continue)
(cond
((null? (cdr args))
(warn "usage: @meta-module-is <module>"))
((eval `(load-module ',(cadr args)) (repl-meta-env rp))
=> (lambda (m) (repl-meta-env-set! rp (module-env m))))
(else
(warn "couldn't find module:" (cadr args))))
(continue rp))
(define (repl/help rp args meta continue)
(let ((out (repl-out rp)))
(cond
((null? (cdr args))
(display "Try @help <identifier> [<module>]\n" out))
((null? (cddr args))
(let* ((failed (list 'failed))
(val (protect (exn (else (print-exception exn) failed))
(eval (second args) (repl-env rp))))
(mod (and (procedure? val) (containing-module val))))
(cond
(mod
(write val out) (newline out) (newline out)
(print-module-binding-docs (car mod) (second args) out))
((not (eq? val failed))
(describe val out)))))
(else
(protect (exn (else (print-exception exn (current-error-port))))
(print-module-binding-docs (third args) (second args) out))))
(continue rp)))
(define (repl/exit rp args meta continue)
;; To exit the repl simply don't call continue.
#f)
;; Utility to read all objects from a port accumulated into a list.
(define (read/ss/all port)
(let loop ((l '()))
(let ((x (read/ss port)))
(if (eof-object? x)
(reverse l)
(loop (cons x l))))))
(define (string->sexp-list str)
(call-with-input-string str read/ss/all))
;; Utility to provide additional help for common exceptions.
(define (repl-advise-exception exn out)
(cond
((and (exception? exn)
(equal? "undefined variable" (exception-message exn))
(pair? (exception-irritants exn)))
(let ((name (car (exception-irritants exn))))
(cond
((identifier? name)
(display "Searching for modules exporting " out)
(display name out)
(display " ...\n" out)
(let ((mods (modules-exporting-identifier name)))
(cond
((pair? mods)
(display name out)
(display " is exported by:\n" out)
(for-each
(lambda (m)
(display " " out) (write m out) (newline out))
(sort (map car mods)
(lambda (a b)
(string<? (write-to-string a) (write-to-string b))))))
(else
(display "... none found.\n" out))))))))))
(define (repl/eval rp expr-list)
(let ((out (repl-out rp)))
(protect (exn (else (print-exception exn out)))
(let ((thread
(make-thread
(lambda ()
;; The inner protect in the child thread catches errors
;; from eval.
(protect (exn
(else
(print-exception exn out)
(repl-advise-exception exn (current-error-port))))
(for-each
(lambda (expr)
(call-with-values
(lambda ()
(if (or (identifier? expr)
(pair? expr)
(null? expr))
(eval expr (repl-env rp))
expr))
(lambda res-list
(cond
((not (or (null? res-list)
(equal? res-list (list (if #f #f)))))
(write/ss (car res-list) out)
(for-each
(lambda (res)
(write-char #\space out)
(write/ss res out))
(cdr res-list))
(newline out))))))
expr-list))))))
;; If an interrupt occurs while the child thread is
;; still running, terminate it, otherwise wait for it
;; to complete.
(with-signal-handler
signal/interrupt
(lambda (n)
(display "\nInterrupt\n" out)
(thread-terminate! thread))
(lambda () (thread-join! (thread-start! thread))))))))
(define (repl/eval-string rp str)
(repl/eval
rp
(protect (exn (else (print-exception exn (current-error-port))))
;; Ugly wrapper to account for the implicit state mutation
;; implied by the #!fold-case read syntax.
(let ((in (repl-in rp))
(in2 (open-input-string str)))
(set-port-fold-case! in2 (port-fold-case? in))
(set-port-line! in2 (port-line in))
(let ((expr-list (read/ss/all in2)))
(set-port-fold-case! in (port-fold-case? in2))
expr-list)))))
(define (keywords->repl ls)
(let-keywords* ls
((in in: (current-input-port))
(out out: (current-output-port))
(escape escape: #\@)
(module module: #f)
(env
environment:
(if module
(module-env
(if (module? module) module (load-module module)))
(interaction-environment)))
(make-prompt
make-prompt:
(lambda (module)
(string-append (if module (write-to-string module) "") "> ")))
(history-file
history-file:
(string-append (get-environment-variable "HOME")
"/.chibi-repl-history"))
(history
history:
(or (protect (exn (else #f))
(list->history (call-with-input-file history-file read)))
(make-history)))
(raw? raw?:
(member (get-environment-variable "TERM") '("emacs" "dumb")))
(meta-env meta-env: (module-env (load-module '(meta)))))
(make-repl
in out escape module env meta-env make-prompt history-file history raw?)))
(define (repl/edit-line rp)
(let ((prompt ((repl-make-prompt rp) (repl-module rp)))
(in (repl-in rp))
(out (repl-out rp)))
(cond
((repl-raw? rp)
(display prompt out)
(flush-output out)
(read-line/complete-sexp in))
(else
(edit-line in out
'prompt: prompt
'history: (repl-history rp)
'complete?: buffer-complete-sexp?
'completion: (make-sexp-buffer-completer)
'catch-control-c?: #t
'fresh-line: " \x1B;[33m\\\x1B;[0m")))))
(define repl-commands
`((import . ,repl/import)
(import-only . ,repl/import-only)
(in . ,repl/in)
(meta . ,repl/meta)
(meta-module-is . ,repl/meta-module-is)
(? . ,repl/help)
(h . ,repl/help)
(help . ,repl/help)
(exit . ,repl/exit)))
(define (repl . o)
(let ((rp (keywords->repl o)))
(let lp ((rp rp))
(let ((line (repl/edit-line rp)))
(cond
((or (not line) (eof-object? line)))
((equal? line "")
(history-reset! (repl-history rp))
(lp rp))
(else
(history-commit! (repl-history rp) line)
(cond
((and (> (string-length line) 1)
(eqv? (repl-escape rp) (string-ref line 0)))
;; @ escaped command
(let meta ((rp rp)
(args (string->sexp-list (substring line 1)))
(continue lp))
(cond
((null? args)
(warn "empty repl command")
(continue rp))
((assq (car args) repl-commands)
=> (lambda (x) ((cdr x) rp args meta continue)))
(else
(warn "unknown repl command" (car args))
(continue rp)))))
(else
;; Normal expression to eval.
(repl/eval-string rp line)
(lp rp)))))))
;; Update the history file on completion.
(if (repl-history-file rp)
(protect
(exn
(else
(let ((msg (integer->error-string)))
(display "couldn't save repl history: " (current-error-port))
(display msg (current-error-port))
(newline (current-error-port)))))
(call-with-output-file (repl-history-file rp)
(lambda (out) (write (history->list (repl-history rp)) out)))))))
(define (main args)
(repl))