4 use Sub::Exporter -setup => {
5 exports => [qw(eval_closure)],
6 groups => { default => [qw(eval_closure)] },
8 # ABSTRACT: safely and cleanly create closures via string eval
13 use Scalar::Util qw(reftype);
20 my $code = eval_closure(
21 source => 'sub { $foo++ }',
30 my $code2 = eval_closure(
31 source => 'sub { $code->() }',
32 ); # dies, $code isn't in scope
36 String eval is often used for dynamic code generation. For instance, C<Moose>
37 uses it heavily, to generate inlined versions of accessors and constructors,
38 which speeds code up at runtime by a significant amount. String eval is not
39 without its issues however - it's difficult to control the scope it's used in
40 (which determines which variables are in scope inside the eval), and it can be
41 quite slow, especially if doing a large number of evals.
43 This module attempts to solve both of those problems. It provides an
44 C<eval_closure> function, which evals a string in a clean environment, other
45 than a fixed list of specified variables. It also caches the result of the
46 eval, so that doing repeated evals of the same source, even with a different
47 environment, will be much faster (but note that the description is part of the
48 string to be evaled, so it must also be the same (or non-existent) if caching
53 =func eval_closure(%args)
55 This function provides the main functionality of this module. It is exported by
56 default. It takes a hash of parameters, with these keys being valid:
62 The string to be evaled. It should end by returning a code reference. It can
63 access any variable declared in the C<environment> parameter (and only those
64 variables). It can be either a string, or an arrayref of lines (which will be
65 joined with newlines to produce the string).
69 The environment to provide to the eval. This should be a hashref, mapping
70 variable names (including sigils) to references of the appropriate type. For
71 instance, a valid value for environment would be C<< { '@foo' => [] } >> (which
72 would allow the generated function to use an array named C<@foo>). Generally,
73 this is used to allow the generated function to access externally defined
74 variables (so you would pass in a reference to a variable that already exists).
78 This lets you provide a bit more information in backtraces. Normally, when a
79 function that was generated through string eval is called, that stack frame
80 will show up as "(eval n)", where 'n' is a sequential identifier for every
81 string eval that has happened so far in the program. Passing a C<description>
82 parameter lets you override that to something more useful (for instance,
83 L<Moose> overrides the description for accessors to something like "accessor
84 foo at MyClass.pm, line 123").
88 Normally, this function appends the source code that failed to compile, and
89 prepends some explanatory text. Setting this option to true suppresses that
90 behavior so you get only the compilation error that Perl actually reported.
99 $args{source} = _canonicalize_source($args{source});
100 _validate_env($args{environment} ||= {});
102 $args{source} = _line_directive($args{description}) . $args{source}
103 if defined $args{description};
105 my ($code, $e) = _clean_eval_closure(@args{qw(source environment)});
108 if ($args{terse_error}) {
112 croak("Failed to compile source: $e\n\nsource:\n$args{source}")
119 sub _canonicalize_source {
122 if (defined($source)) {
124 if (reftype($source) eq 'ARRAY'
125 || overload::Method($source, '@{}')) {
126 return join "\n", @$source;
128 elsif (overload::Method($source, '""')) {
132 croak("The 'source' parameter to eval_closure must be a "
133 . "string or array reference");
141 croak("The 'source' parameter to eval_closure is required");
148 croak("The 'environment' parameter must be a hashref")
149 unless reftype($env) eq 'HASH';
151 for my $var (keys %$env) {
152 croak("Environment key '$var' should start with \@, \%, or \$")
153 unless $var =~ /^([\@\%\$])/;
154 croak("Environment values must be references, not $env->{$var}")
155 unless ref($env->{$var});
159 sub _line_directive {
160 my ($description) = @_;
162 return qq{#line 1 "$description"\n};
165 sub _clean_eval_closure {
166 my ($source, $captures) = @_;
168 if ($ENV{EVAL_CLOSURE_PRINT_SOURCE}) {
169 _dump_source(_make_compiler_source(@_));
172 my @capture_keys = sort keys %$captures;
173 my ($compiler, $e) = _make_compiler($source, @capture_keys);
175 if (defined $compiler) {
176 $code = $compiler->(@$captures{@capture_keys});
179 if (defined($code) && (!ref($code) || ref($code) ne 'CODE')) {
180 $e = "The 'source' parameter must return a subroutine reference, "
191 my $compiler = eval _make_compiler_source(@_);
193 return ($compiler, $e);
195 memoize('_make_compiler');
197 sub _make_compiler_source {
198 my ($source, @capture_keys) = @_;
203 'my ' . $_ . ' = ' . substr($_, 0, 1) . '{$_[' . $i++ . ']};'
214 if (try { require Perl::Tidy }) {
215 Perl::Tidy::perltidy(
217 destination => \$output,
231 Please report any bugs through RT: email
232 C<bug-eval-closure at rt.cpan.org>, or browse to
233 L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure>.
239 =item * L<Class::MOP::Method::Accessor>
241 This module is a factoring out of code that used to live here
247 You can find this documentation for this module with the perldoc command.
249 perldoc Eval::Closure
251 You can also look for information at:
255 =item * AnnoCPAN: Annotated CPAN documentation
257 L<http://annocpan.org/dist/Eval-Closure>
261 L<http://cpanratings.perl.org/d/Eval-Closure>
263 =item * RT: CPAN's request tracker
265 L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure>
269 L<http://search.cpan.org/dist/Eval-Closure>
275 Jesse Luehrs <doy at tozt dot net>
277 Based on code from L<Class::MOP::Method::Accessor>, by Stevan Little and the