$VERSION = eval $VERSION;
-@EXPORT = @EXPORT_OK = qw(try catch);
+@EXPORT = @EXPORT_OK = qw(try catch finally);
$Carp::Internal{+__PACKAGE__}++;
-sub try (&;$) {
- my ( $try, $catch ) = @_;
+# 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
+
+sub try (&;@) {
+ my ( $try, @code_refs ) = @_;
# we need to save this here, the eval block will be in scalar context due
# to $failed
my $wantarray = wantarray;
+ my ( $catch, $finally );
+
+ # find labeled blocks in the argument list.
+ # catch and finally tag the blocks by blessing a scalar reference to them.
+ foreach my $code_ref (@code_refs) {
+ next unless $code_ref;
+
+ my $ref = ref($code_ref);
+
+ if ( $ref eq 'Try::Tiny::Catch' ) {
+ $catch = ${$code_ref};
+ } elsif ( $ref eq 'Try::Tiny::Finally' ) {
+ $finally = ${$code_ref};
+ } else {
+ use Carp;
+ confess("Unknown code ref type given '${ref}'. Check your usage & try again");
+ }
+ }
+
# save the value of $@ so we can set $@ back to it in the beginning of the eval
my $prev_error = $@;
# This works like given($error), but is backwards compatible and
# sets $_ in the dynamic scope for the body of C<$catch>
for ($error) {
- return $catch->($error);
+ my $catch_return = $catch->($error);
+
+ # Finally blocks run after all other blocks so it is executed here
+ $finally->() if ( $finally );
+
+ #And return whatever catch returned
+ return $catch_return;
}
# in case when() was used without an explicit return, the C<for>
return;
} else {
+ # Execute finally block once we decided we worked
+ $finally->() if ( $finally );
+
# no failure, $@ is back to what it was, everything is fine
return $wantarray ? @ret : $ret[0];
}
}
-sub catch (&) {
- return $_[0];
+sub catch (&;@) {
+ my ( $block, @rest ) = @_;
+
+ return (
+ bless(\$block, 'Try::Tiny::Catch'),
+ @rest,
+ );
}
+sub finally (&;@) {
+ my ( $block, @rest ) = @_;
+
+ return (
+ bless(\$block, 'Try::Tiny::Finally'),
+ @rest,
+ );
+}
__PACKAGE__
=head1 DESCRIPTION
-This module provides bare bones C<try>/C<catch> statements that are designed to
+This module provides bare bones C<try>/C<catch>/C<finally> statements that are designed to
minimize common mistakes with eval blocks, and NOTHING else.
This is unlike L<TryCatch> which provides a nice syntax and avoids adding
of error values (simple strings, references, objects, overloaded objects, etc).
If the try block dies, it returns the value of the last statement executed in
-the catch block, if there is one. Otherwise, it returns C<undef> in scalar
+the catch block, if there is one. Otherwise, it returns C<undef> in scalar
context or the empty list in list context. The following two examples both
assign C<"bar"> to C<$x>.
my $x = eval { die "foo" } || "bar";
+You can add finally blocks making the following true.
+
+ my $x;
+ try { die 'foo' } finally { $x = 'bar' };
+ try { die 'foo' } catch { warn "Got a die: $_" } finally { $x = 'bar' };
+
+Finally blocks are always executed making them suitable for cleanup code
+which cannot be handled using local.
+
=head1 EXPORTS
All functions are exported by default using L<Exporter>.
-If you need to rename the C<try> or C<catch> keyword consider using
+If you need to rename the C<try>, C<catch> or C<finally> keyword consider using
L<Sub::Import> to get L<Sub::Exporter>'s flexibility.
=over 4
-=item try (&;$)
+=item try (&;@)
-Takes one mandatory try subroutine and one optional catch subroutine.
+Takes one mandatory try subroutine, an optional catch subroutine & finally
+subroutine.
The mandatory subroutine is evaluated in the context of an C<eval> block.
Note that the error may be false, but if that happens the C<catch> block will
still be invoked.
-=item catch (&)
+Once all execution is finished then the finally block if given will execute.
+
+=item catch (&;$)
Intended to be used in the second argument position of C<try>.
-Just returns the subroutine it was given.
+Returns a reference to the subroutine it was given but blessed as
+C<Try::Tiny::Catch> which allows try to decode correctly what to do
+with this code reference.
catch { ... }
-is the same as
-
- sub { ... }
-
Inside the catch block the previous value of C<$@> is still available for use.
This value may or may not be meaningful depending on what happened before the
C<try>, but it might be a good idea to preserve it in an error stack.
+=item finally (&;$)
+
+ try { ... }
+ catch { ... }
+ finally { ... };
+
+Or
+
+ try { ... }
+ finally { ... };
+
+Or even
+
+ try { ... }
+ finally { ... }
+ catch { ... };
+
+Intended to be the second or third element of C<try>. Finally blocks are always
+executed in the event of a successful C<try> or if C<catch> is run. This allows
+you to locate cleanup code which cannot be done via C<local()> e.g. closing a file
+handle.
+
+B<You must always do your own error handling in the finally block>. C<Try::Tiny> will
+not do anything about handling possible errors coming from code located in these
+blocks.
+
+In the same way C<catch()> blesses the code reference this subroutine does the same
+except it bless them as C<Try::Tiny::Finally>.
+
=back
=head1 BACKGROUND
projects / p5sagit/Try-Tiny.git / blobdiff