echo: Implement escapes.

* gash/built-ins/echo.scm (escape->control): New function.
(echo): Support '-e' and '-E' options even when clumped.
* Makefile.am (XFAIL_TESTS): Remove tests/20-pipe-sed.sh.

Co-authored-by: Timothy Sample <samplet@ngyro.com>

Makefile.am

@@ -237,7 +237,6 @@ FULL_TESTS =                                    \
 TESTS = $(UNIT_TESTS) $(FULL_TESTS)
 
 XFAIL_TESTS =                                   \
-  tests/20-pipe-sed.sh                          \
   tests/70-hash.sh                              \
   tests/70-hash-hash.sh                         \
   tests/70-percent.sh                           \

gash/built-ins/echo.scm

@@ -1,5 +1,6 @@
 ;;; Gash -- Guile As SHell
-;;; Copyright © 2018 Timothy Sample <samplet@ngyro.com>
+;;; Copyright © 2018, 2019 Timothy Sample <samplet@ngyro.com>
+;;; Copyright © 2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
 ;;;
 ;;; This file is part of Gash.
 ;;;
@@ -17,6 +18,9 @@
 ;;; along with Gash.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gash built-ins echo)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
   #:export (echo))
 
 ;;; Commentary:
@@ -25,10 +29,50 @@
 ;;;
 ;;; Code:
 
+(define (escape->control string)
+  (list->string
+   (let loop ((lst (string->list string)))
+     (if (null? lst) '()
+         (let ((char (car lst)))
+           (if (or (not (eq? char #\\))
+                   (null? (cdr lst))) (cons char (loop (cdr lst)))
+                   (let* ((lst (cdr lst))
+                          (char (car lst)))
+                     (case char
+                       ((#\\) (cons #\\ (loop (cdr lst))))
+                       ((#\a) (cons #\alarm (loop (cdr lst))))
+                       ((#\b) (cons #\backspace (loop (cdr lst))))
+                       ((#\c) '())
+                       ((#\e) (cons #\escape (loop (cdr lst))))
+                       ((#\f) (cons #\page (loop (cdr lst))))
+                       ((#\n) (cons #\newline (loop (cdr lst))))
+                       ((#\r) (cons #\return (loop (cdr lst))))
+                       ((#\t) (cons #\tab (loop (cdr lst))))
+                       ((#\v) (cons #\vtab (loop (cdr lst))))
+                       ((#\0) (error "echo: TODO: \\0NNN"))
+                       ((#\x) (error "echo: TODO: \\xNNN"))))))))))
+
+(define (option? str)
+  (and (> (string-length str) 1)
+       (char=? (string-ref str 0) #\-)
+       (string-every (cut member <> '(#\E #\e #\n)) (substring str 1))))
+
 (define (echo . args)
-  (let* ((n? (and (pair? args) (string=? (car args) "-n")))
-         (args (if n? (cdr args) args)))
-    (display (string-join args " "))
-    (unless n?
+  (let* ((options (append-map (compose cdr string->list)
+                              (take-while option? args)))
+         (args (drop-while option? args))
+         (newline? (not (member #\n options)))
+         (escapes? (fold (lambda (x acc)
+                           (match x
+                             (#\e #t)
+                             (#\E #f)
+                             (_ acc)))
+                         #f
+                         options))
+         (string (string-join args)))
+    (display (if escapes?
+                 (escape->control string)
+                 string))
+    (when newline?
       (newline))
     0))