Add warning to POD about try/finally

[p5sagit/Try-Tiny.git] / lib / Try / Tiny.pm

diff --git a/lib/Try/Tiny.pm b/lib/Try/Tiny.pm
index c3c74a9..91307b4 100644 (file)
--- a/lib/Try/Tiny.pm
+++ b/lib/Try/Tiny.pm
@@ -5,12 +5,14 @@ use 5.006;
 use strict;
 use warnings;
 
-use base 'Exporter';
+use Exporter 5.57 'import';
 our @EXPORT = our @EXPORT_OK = qw(try catch finally);
 
 use Carp;
 $Carp::Internal{+__PACKAGE__}++;
 
+BEGIN { eval "use Sub::Name; 1" or *{subname} = sub {1} }
+
 # Need to prototype as @ not $$ because of the way Perl evaluates the prototype.
 # Keeping it at $$ means you only ever get 1 sub because we need to eval in a list
 # context & not a scalar one
@@ -22,7 +24,9 @@ sub try (&;@) {
   # to $failed
   my $wantarray = wantarray;
 
-  my ( $catch, @finally );
+  # work around perl bug by explicitly initializing these, due to the likelyhood
+  # this will be used in global destruction (perl rt#119311)
+  my ( $catch, @finally ) = ();
 
   # find labeled blocks in the argument list.
   # catch and finally tag the blocks by blessing a scalar reference to them.
@@ -47,6 +51,12 @@ sub try (&;@) {
   # not perfect, but we could provide a list of additional errors for
   # $catch->();
 
+  # name the blocks if we have Sub::Name installed
+  my $caller = caller;
+  subname("${caller}::try {...} " => $try);
+  subname("${caller}::catch {...} " => $catch) if $catch;
+  subname("${caller}::finally {...} " => $_) foreach @finally;
+
   # save the value of $@ so we can set $@ back to it in the beginning of the eval
   # and restore $@ after the eval finishes
   my $prev_error = $@;
@@ -104,7 +114,7 @@ sub try (&;@) {
 sub catch (&;@) {
   my ( $block, @rest ) = @_;
 
-  croak 'Useless bare catch()' unless defined wantarray;
+  croak 'Useless bare catch()' unless wantarray;
 
   return (
     bless(\$block, 'Try::Tiny::Catch'),
@@ -115,7 +125,7 @@ sub catch (&;@) {
 sub finally (&;@) {
   my ( $block, @rest ) = @_;
 
-  croak 'Useless bare finally()' unless defined wantarray;
+  croak 'Useless bare finally()' unless wantarray;
 
   return (
     bless(\$block, 'Try::Tiny::Finally'),
@@ -222,6 +232,13 @@ C<finally> blocks are always executed making them suitable for cleanup code
 which cannot be handled using local.  You can add as many C<finally> blocks to a
 given C<try> block as you like.
 
+Note that adding a C<finally> block without a preceding C<catch> block
+suppresses any errors. This behaviour is consistent with using a standalone
+C<eval>, but it is not consistent with C<try>/C<finally> patterns found in
+other programming languages, such as Java, Python, Javascript or C#. If you
+learnt the C<try>/C<finally> pattern from one of these languages, watch out for
+this.
+
 =head1 EXPORTS
 
 All functions are exported by default using L<Exporter>.
@@ -485,7 +502,21 @@ Instead, you should capture the return value:
     my $success = try {
       die;
       1;
+    };
+    return unless $success;
+
+    say "This text WILL NEVER appear!";
+  }
+  # OR
+  sub parent_sub_with_catch {
+    my $success = try {
+      die;
+      1;
     }
+    catch {
+      # do something with $_
+      return undef; #see note
+    };
     return unless $success;
 
     say "This text WILL NEVER appear!";
@@ -605,7 +636,7 @@ L<http://web.archive.org/web/20100305133605/http://nothingmuch.woobling.org/talk
 
 =head1 VERSION CONTROL
 
-L<http://github.com/nothingmuch/try-tiny/>
+L<http://github.com/doy/try-tiny/>
 
 =cut