Do not scan for coding declarations in open-file.

* libguile/fports.c (scm_open_file): Do not scan for coding
  declarations.  Replace 'use_encoding' local variable with
  'binary'.  Update documentation string.

* module/ice-9/psyntax.scm (include): Add the same file-encoding
  logic that's used in compile-file and scm_primitive_load.

* module/ice-9/psyntax-pp.scm: Regenerate.

* doc/ref/api-io.texi (File Ports): Update docs.

* test-suite/tests/ports.test: Change "open-file HONORS file coding
  declarations" test to "open-file IGNORES file coding declaration".

* test-suite/tests/coding.test (scan-coding): Use 'file-encoding' to
  scan for the encoding, since 'open-input-file' no longer does so.

doc/ref/api-io.texi

@@ -885,8 +885,8 @@ Use binary mode, ensuring that each byte in the file will be read as one
 Scheme character.
 
 To provide this property, the file will be opened with the 8-bit
-character encoding "ISO-8859-1", ignoring any coding declaration or port
+character encoding "ISO-8859-1", ignoring the default port encoding.
-encoding.  @xref{Ports}, for more information on port encodings.
+@xref{Ports}, for more information on port encodings.
 
 Note that while it is possible to read and write binary data as
 characters or strings, it is usually better to treat bytes as octets,
@@ -903,12 +903,20 @@ because of its port encoding ramifications.
 If a file cannot be opened with the access
 requested, @code{open-file} throws an exception.
 
-When the file is opened, this procedure will scan for a coding
+When the file is opened, its encoding is set to the current
-declaration (@pxref{Character Encoding of Source Files}). If a coding
+@code{%default-port-encoding}, unless the @code{b} flag was supplied.
-declaration is found, it will be used to interpret the file.  Otherwise,
+Sometimes it is desirable to honor Emacs-style coding declarations in
-the port's encoding will be used.  To suppress this behavior, open the
+files@footnote{Guile 2.0.0 to 2.0.7 would do this by default.  This
-file in binary mode and then set the port encoding explicitly using
+behavior was deemed inappropriate and disabled starting from Guile
-@code{set-port-encoding!}.
+2.0.8.}.  When that is the case, the @code{file-encoding} procedure can
+be used as follows (@pxref{Character Encoding of Source Files,
+@code{file-encoding}}):
+
+@example
+(let* ((port     (open-input-file file))
+       (encoding (file-encoding port)))
+  (set-port-encoding! port (or encoding (port-encoding port))))
+@end example
 
 In theory we could create read/write ports which were buffered
 in one direction only.  However this isn't included in the

libguile/fports.c

@@ -349,8 +349,7 @@ SCM_DEFINE (scm_open_file, "open-file", 2, 0, 0,
 	    "@item b\n"
 	    "Open the underlying file in binary mode, if supported by the system.\n"
 	    "Also, open the file using the binary-compatible character encoding\n"
-	    "\"ISO-8859-1\", ignoring the port's encoding and the coding declaration\n"
+	    "\"ISO-8859-1\", ignoring the default port encoding.\n"
-	    "at the top of the input file, if any.\n"
 	    "@item +\n"
 	    "Open the port for both input and output.  E.g., @code{r+}: open\n"
 	    "an existing file for both input and output.\n"
@@ -365,11 +364,6 @@ SCM_DEFINE (scm_open_file, "open-file", 2, 0, 0,
 	    "Add line-buffering to the port.  The port output buffer will be\n"
 	    "automatically flushed whenever a newline character is written.\n"
 	    "@end table\n"
-	    "When the file is opened, this procedure will scan for a coding\n"
-	    "declaration@pxref{Character Encoding of Source Files}. If present\n"
-	    "will use that encoding for interpreting the file.  Otherwise, the\n"
-	    "port's encoding will be used.\n"
-	    "\n"
 	    "In theory we could create read/write ports which were buffered\n"
 	    "in one direction only.  However this isn't included in the\n"
 	    "current interfaces.  If a file cannot be opened with the access\n"
@@ -377,7 +371,7 @@ SCM_DEFINE (scm_open_file, "open-file", 2, 0, 0,
 #define FUNC_NAME s_scm_open_file
 {
   SCM port;
-  int fdes, flags = 0, use_encoding = 1;
+  int fdes, flags = 0, binary = 0;
   unsigned int retries;
   char *file, *md, *ptr;
 
@@ -412,7 +406,7 @@ SCM_DEFINE (scm_open_file, "open-file", 2, 0, 0,
 	  flags = (flags & ~(O_RDONLY | O_WRONLY)) | O_RDWR;
 	  break;
 	case 'b':
-	  use_encoding = 0;
+	  binary = 1;
 #if defined (O_BINARY)
 	  flags |= O_BINARY;
 #endif
@@ -451,20 +445,8 @@ SCM_DEFINE (scm_open_file, "open-file", 2, 0, 0,
   port = scm_i_fdes_to_port (fdes, scm_i_mode_bits (mode),
                              fport_canonicalize_filename (filename));
 
-  if (use_encoding)
+  if (binary)
-    {
+    /* Use the binary-friendly ISO-8859-1 encoding. */
-      /* If this file has a coding declaration, use that as the port
-	 encoding.  */
-      if (SCM_INPUT_PORT_P (port))
-	{
-	  char *enc = scm_i_scan_for_encoding (port);
-	  if (enc != NULL)
-	    scm_i_set_port_encoding_x (port, enc);
-	}
-    }
-  else
-    /* If this is a binary file, use the binary-friendly ISO-8859-1
-       encoding.  */
     scm_i_set_port_encoding_x (port, NULL);
 
   scm_dynwind_end ();

module/ice-9/psyntax-pp.scm

@@ -2975,10 +2975,12 @@
            (lambda (fn dir k)
              (let ((p (open-input-file
                         (if (absolute-file-name? fn) fn (in-vicinity dir fn)))))
-               (let f ((x (read p)) (result '()))
+               (let ((enc (file-encoding p)))
-                 (if (eof-object? x)
+                 (set-port-encoding! p (let ((t enc)) (if t t "UTF-8")))
-                   (begin (close-input-port p) (reverse result))
+                 (let f ((x (read p)) (result '()))
-                   (f (read p) (cons (datum->syntax k x) result))))))))
+                   (if (eof-object? x)
+                     (begin (close-input-port p) (reverse result))
+                     (f (read p) (cons (datum->syntax k x) result)))))))))
         (let ((src (syntax-source x)))
           (let ((file (if src (assq-ref src 'filename) #f)))
             (let ((dir (if (string? file) (dirname file) #f)))

module/ice-9/psyntax.scm

@@ -2945,10 +2945,15 @@
   (lambda (x)
     (define read-file
       (lambda (fn dir k)
-        (let ((p (open-input-file
+        (let* ((p (open-input-file
-                  (if (absolute-file-name? fn)
+                   (if (absolute-file-name? fn)
-                      fn
+                       fn
-                      (in-vicinity dir fn)))))
+                       (in-vicinity dir fn))))
+               (enc (file-encoding p)))
+
+          ;; Choose the input encoding deterministically.
+          (set-port-encoding! p (or enc "UTF-8"))
+
           (let f ((x (read p))
                   (result '()))
             (if (eof-object? x)

test-suite/tests/coding.test

@@ -1,6 +1,6 @@
 ;;;; coding.test --- test suite for coding declarations. -*- mode: scheme -*-
 ;;;;
-;;;; Copyright (C) 2011 Free Software Foundation, Inc.
+;;;; Copyright (C) 2011, 2013 Free Software Foundation, Inc.
 ;;;;
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -40,7 +40,7 @@
      ;; relies on the opportunistic filling of the input buffer, which
      ;; doesn't happen after a seek.
      (let* ((port (open-input-file name))
-            (res (port-encoding port)))
+            (res (file-encoding port)))
        (close-port port)
        res))))
 

test-suite/tests/ports.test

@@ -270,13 +270,12 @@
                    (delete-file filename)
                    (string=? line2 binary-test-string)))))
 
-;; open-file honors file coding declarations
+;; open-file ignores file coding declaration
-(pass-if "file: open-file honors coding declarations"
+(pass-if "file: open-file ignores coding declarations"
   (with-fluids ((%default-port-encoding "UTF-8"))
                (let* ((filename (test-file))
                       (port (open-output-file filename))
                       (test-string "€100"))
-                 (set-port-encoding! port "ISO-8859-15")
                  (write-line ";; coding: iso-8859-15" port)
                  (write-line test-string port)
                  (close-port port)