[NUUG fiksgatami] [patch] Use throw to report errors in mySociety::Config

[Petter Reinholdtsen]

When there is an error in the configuration, an empty Error exception
is displayed on the front page.  The reason is that the die messages
sent from the mySociety::Config module is not made part of any Error
exception, and thus not displayed.  I recommend changing the
mySociety::Config module to use throw instead of die to report
problems.  Here is a patch to do just that.  With this change in
place, it was trivial to figure out which configuration variable was
incorrect.

Index: perllib/mySociety/Config.pm
===================================================================
RCS file: /repos/mysociety/perllib/mySociety/Config.pm,v
retrieving revision 1.18
diff -u -3 -p -r1.18 Config.pm
--- perllib/mySociety/Config.pm 10 Apr 2008 15:41:40 -0000      1.18
+++ perllib/mySociety/Config.pm 24 Jan 2009 09:57:26 -0000
@@ -52,7 +52,7 @@ sub find_php () {
             return "$dir/$name" if (-x "$dir/$name");
         }
     }
-    die "unable to locate PHP binary, needed to read config file";
+    throw Error::Simple "unable to locate PHP binary, needed to read config file";
 }

 =item read_config FILE [DEFAULTS]
@@ -68,7 +68,7 @@ sub read_config ($;$) {
     my ($f, $defaults) = @_;

     if (! -r $f) {
-        die "$f: read permissions not OK for config file";
+        throw Error::Simple "$f: read permissions not OK for config file";
     }

     my $old_SIGCHLD = $SIG{CHLD};
@@ -89,7 +89,7 @@ sub read_config ($;$) {
     my $p2 = new IO::Pipe($inr, $inw);

     my $pid = fork();
-    die "fork: $!" unless (defined($pid));
+    throw Error::Simple "fork: $!" unless (defined($pid));
     if ($pid == 0) {
         # Delete everything from the environment other than our special
         # variable to give PHP the config file name. We don't want PHP to pick
@@ -107,7 +107,7 @@ sub read_config ($;$) {
         $inr->close();
         $outw->close();

-        exec($php_path) or die "$php_path: exec: $!";
+        exec($php_path) or throw Error::Simple "$php_path: exec: $!";
     }

     $inr->close();
@@ -138,9 +138,9 @@ EOF

     if (!defined($line)) {
         if ($outr->error()) {
-            die "$php_path: $f: $!";
+            throw Error::Simple "$php_path: $f: $!";
         } else {
-            die "$php_path: $f: no option output from subprocess";
+            throw Error::Simple "$php_path: $f: no option output from subprocess";
         }
     }

@@ -151,7 +151,7 @@ EOF
     pop(@vals); # The buffer ends "\0" so there's always a trailing empty value
                 # at the end of the buffer. I love perl! Perl is my friend!

-    die "$php_path: $f: bad option output from subprocess" if (scalar(@vals) % 2);
+    throw Error::Simple "$php_path: $f: bad option output from subprocess" if (scalar(@vals) % 2);

     my %config = @vals;

@@ -163,9 +163,9 @@ EOF

     if ($?) {
         if ($? & 127) {
-            die "$php_path: killed by signal " . ($? & 127);
+            throw Error::Simple "$php_path: killed by signal " . ($? & 127);
         } else {
-            die "$php_path: exited with failure status " . ($? >> 8);
+            throw Error::Simple "$php_path: exited with failure status " . ($? >> 8);
         }
     }

@@ -199,7 +199,7 @@ function is implicitly called by get and
 my %cached_configs;
 sub load_default() {
     my $filename = $main_config_filename;
-    die "Please call mySociety::Config::set_file to specify config file" if (!defined($filename));
+    throw Error::Simple "Please call mySociety::Config::set_file to specify config file" if (!defined($filename));

     if (!defined($cached_configs{$filename})) {
         $cached_configs{$filename} = read_config($filename);
@@ -224,7 +224,7 @@ sub get ($;$) {
     } elsif (@_ == 2) {
         return $default;
     } else {
-        die "No value for '$key' in '" . $config->{'CONFIG_FILE_NAME'} .  "', and no default specified";
+        throw Error::Simple "No value for '$key' in '" . $config->{'CONFIG_FILE_NAME'} .  "', and no default specified";
     }
 }