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
12 use Scalar::Util qw(reftype);
19 my $code = eval_closure(
20 source => 'sub { $foo++ }',
29 my $code2 = eval_closure(
30 source => 'sub { $code->() }',
31 ); # dies, $code isn't in scope
35 String eval is often used for dynamic code generation. For instance, C<Moose>
36 uses it heavily, to generate inlined versions of accessors and constructors,
37 which speeds code up at runtime by a significant amount. String eval is not
38 without its issues however - it's difficult to control the scope it's used in
39 (which determines which variables are in scope inside the eval), and it's easy
40 to miss compilation errors, since eval catches them and sticks them in $@
43 This module attempts to solve these problems. It provides an C<eval_closure>
44 function, which evals a string in a clean environment, other than a fixed list
45 of specified variables. Compilation errors are rethrown automatically.
49 =func eval_closure(%args)
51 This function provides the main functionality of this module. It is exported by
52 default. It takes a hash of parameters, with these keys being valid:
58 The string to be evaled. It should end by returning a code reference. It can
59 access any variable declared in the C<environment> parameter (and only those
60 variables). It can be either a string, or an arrayref of lines (which will be
61 joined with newlines to produce the string).
65 The environment to provide to the eval. This should be a hashref, mapping
66 variable names (including sigils) to references of the appropriate type. For
67 instance, a valid value for environment would be C<< { '@foo' => [] } >> (which
68 would allow the generated function to use an array named C<@foo>). Generally,
69 this is used to allow the generated function to access externally defined
70 variables (so you would pass in a reference to a variable that already exists).
74 This lets you provide a bit more information in backtraces. Normally, when a
75 function that was generated through string eval is called, that stack frame
76 will show up as "(eval n)", where 'n' is a sequential identifier for every
77 string eval that has happened so far in the program. Passing a C<description>
78 parameter lets you override that to something more useful (for instance,
79 L<Moose> overrides the description for accessors to something like "accessor
80 foo at MyClass.pm, line 123").
84 This lets you override the particular line number that appears in backtraces,
85 much like the C<description> option. The default is 1.
89 Normally, this function appends the source code that failed to compile, and
90 prepends some explanatory text. Setting this option to true suppresses that
91 behavior so you get only the compilation error that Perl actually reported.
100 $args{source} = _canonicalize_source($args{source});
101 _validate_env($args{environment} ||= {});
103 $args{source} = _line_directive(@args{qw(line description)})
105 if defined $args{description} && !($^P & 0x10);
107 my ($code, $e) = _clean_eval_closure(@args{qw(source environment)});
110 if ($args{terse_error}) {
114 croak("Failed to compile source: $e\n\nsource:\n$args{source}")
121 sub _canonicalize_source {
124 if (defined($source)) {
126 if (reftype($source) eq 'ARRAY'
127 || overload::Method($source, '@{}')) {
128 return join "\n", @$source;
130 elsif (overload::Method($source, '""')) {
134 croak("The 'source' parameter to eval_closure must be a "
135 . "string or array reference");
143 croak("The 'source' parameter to eval_closure is required");
150 croak("The 'environment' parameter must be a hashref")
151 unless reftype($env) eq 'HASH';
153 for my $var (keys %$env) {
154 croak("Environment key '$var' should start with \@, \%, or \$")
155 unless $var =~ /^([\@\%\$])/;
156 croak("Environment values must be references, not $env->{$var}")
157 unless ref($env->{$var});
161 sub _line_directive {
162 my ($line, $description) = @_;
164 $line = 1 unless defined($line);
166 return qq{#line $line "$description"\n};
169 sub _clean_eval_closure {
170 my ($source, $captures) = @_;
172 my @capture_keys = sort keys %$captures;
174 if ($ENV{EVAL_CLOSURE_PRINT_SOURCE}) {
175 _dump_source(_make_compiler_source($source, @capture_keys));
178 my ($compiler, $e) = _make_compiler($source, @capture_keys);
180 if (defined $compiler) {
181 $code = $compiler->(@$captures{@capture_keys});
184 if (defined($code) && (!ref($code) || ref($code) ne 'CODE')) {
185 $e = "The 'source' parameter must return a subroutine reference, "
194 my $source = _make_compiler_source(@_);
196 return @{ _clean_eval($source) };
202 my $compiler = eval $_[0];
207 $Eval::Closure::SANDBOX_ID = 0;
209 sub _make_compiler_source {
210 my ($source, @capture_keys) = @_;
211 $Eval::Closure::SANDBOX_ID++;
214 "package Eval::Closure::Sandbox_$Eval::Closure::SANDBOX_ID;",
217 'my ' . $_ . ' = ' . substr($_, 0, 1) . '{$_[' . $i++ . ']};'
228 if (try { require Perl::Tidy }) {
229 Perl::Tidy::perltidy(
231 destination => \$output,
246 Please report any bugs through RT: email
247 C<bug-eval-closure at rt.cpan.org>, or browse to
248 L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure>.
254 =item * L<Class::MOP::Method::Accessor>
256 This module is a factoring out of code that used to live here
262 You can find this documentation for this module with the perldoc command.
264 perldoc Eval::Closure
266 You can also look for information at:
270 =item * AnnoCPAN: Annotated CPAN documentation
272 L<http://annocpan.org/dist/Eval-Closure>
276 L<http://cpanratings.perl.org/d/Eval-Closure>
278 =item * RT: CPAN's request tracker
280 L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure>
284 L<http://search.cpan.org/dist/Eval-Closure>
290 Jesse Luehrs <doy at tozt dot net>
292 Based on code from L<Class::MOP::Method::Accessor>, by Stevan Little and the