Commit | Line | Data |
efb592ef |
1 | package Eval::Closure; |
b3bd5eb8 |
2 | use strict; |
3 | use warnings; |
efb592ef |
4 | use Sub::Exporter -setup => { |
5 | exports => [qw(eval_closure)], |
ce19c70b |
6 | groups => { default => [qw(eval_closure)] }, |
efb592ef |
7 | }; |
ed9a00ae |
8 | # ABSTRACT: safely and cleanly create closures via string eval |
efb592ef |
9 | |
10 | use Carp; |
11 | use overload (); |
61717119 |
12 | use Memoize; |
efb592ef |
13 | use Scalar::Util qw(reftype); |
14 | use Try::Tiny; |
15 | |
ed9a00ae |
16 | =head1 SYNOPSIS |
17 | |
2e6086ab |
18 | use Eval::Closure; |
19 | |
20 | my $code = eval_closure( |
21 | source => 'sub { $foo++ }', |
22 | environment => { |
23 | '$foo' => \1, |
24 | }, |
25 | ); |
26 | |
27 | warn $code->(); # 1 |
28 | warn $code->(); # 2 |
29 | |
30 | my $code2 = eval_closure( |
31 | source => 'sub { $code->() }', |
32 | ); # dies, $code isn't in scope |
33 | |
ed9a00ae |
34 | =head1 DESCRIPTION |
35 | |
2e6086ab |
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. |
42 | |
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. |
48 | |
ed9a00ae |
49 | =cut |
50 | |
51 | =func eval_closure(%args) |
52 | |
2e6086ab |
53 | This function provides the main functionality of this module. It is exported by |
54 | default. It takes a hash of parameters, with these keys being valid: |
55 | |
56 | =over 4 |
57 | |
58 | =item source |
59 | |
60 | The string to be evaled. It should end by returning a code reference. It can |
61 | access any variable declared in the C<environment> parameter (and only those |
62 | variables). It can be either a string, or an arrayref of lines (which will be |
63 | joined with newlines to produce the string). |
64 | |
65 | =item environment |
66 | |
67 | The environment to provide to the eval. This should be a hashref, mapping |
68 | variable names (including sigils) to references of the appropriate type. For |
69 | instance, a valid value for environment would be C<< { '@foo' => [] } >> (which |
70 | would allow the generated function to use an array named C<@foo>). Generally, |
71 | this is used to allow the generated function to access externally defined |
72 | variables (so you would pass in a reference to a variable that already exists). |
73 | |
74 | =item description |
75 | |
76 | This lets you provide a bit more information in backtraces. Normally, when a |
77 | function that was generated through string eval is called, that stack frame |
78 | will show up as "(eval n)", where 'n' is a sequential identifier for every |
79 | string eval that has happened so far in the program. Passing a C<description> |
80 | parameter lets you override that to something more useful (for instance, |
81 | L<Moose> overrides the description for accessors to something like "accessor |
82 | foo at MyClass.pm, like 123"). |
83 | |
84 | =back |
85 | |
ed9a00ae |
86 | =cut |
87 | |
efb592ef |
88 | sub eval_closure { |
89 | my (%args) = @_; |
8e1b3d7b |
90 | |
efb592ef |
91 | $args{source} = _canonicalize_source($args{source}); |
8e1b3d7b |
92 | _validate_env($args{environment} ||= {}); |
efb592ef |
93 | |
3efcc087 |
94 | $args{source} = _line_directive($args{description}) . $args{source} |
95 | if defined $args{description}; |
96 | |
409b8f41 |
97 | my ($code, $e) = _clean_eval_closure(@args{qw(source environment)}); |
efb592ef |
98 | |
99 | croak("Failed to compile source: $e\n\nsource:\n$args{source}") |
100 | unless $code; |
101 | |
102 | return $code; |
103 | } |
104 | |
105 | sub _canonicalize_source { |
106 | my ($source) = @_; |
107 | |
108 | if (defined($source)) { |
109 | if (ref($source)) { |
110 | if (reftype($source) eq 'ARRAY' |
111 | || overload::Method($source, '@{}')) { |
112 | return join "\n", @$source; |
113 | } |
114 | elsif (overload::Method($source, '""')) { |
115 | return "$source"; |
116 | } |
117 | else { |
118 | croak("The 'source' parameter to eval_closure must be a " |
119 | . "string or array reference"); |
120 | } |
121 | } |
122 | else { |
123 | return $source; |
124 | } |
125 | } |
126 | else { |
127 | croak("The 'source' parameter to eval_closure is required"); |
128 | } |
129 | } |
130 | |
8e1b3d7b |
131 | sub _validate_env { |
132 | my ($env) = @_; |
133 | |
134 | croak("The 'environment' parameter must be a hashref") |
135 | unless reftype($env) eq 'HASH'; |
136 | |
137 | for my $var (keys %$env) { |
b3bd5eb8 |
138 | croak("Environment key '$var' should start with \@, \%, or \$") |
8e1b3d7b |
139 | unless $var =~ /^([\@\%\$])/; |
140 | croak("Environment values must be references, not $env->{$var}") |
141 | unless ref($env->{$var}); |
142 | } |
143 | } |
144 | |
3efcc087 |
145 | sub _line_directive { |
146 | my ($description) = @_; |
147 | |
148 | return qq{#line 1 "$description"\n}; |
149 | } |
150 | |
efb592ef |
151 | sub _clean_eval_closure { |
f3c27658 |
152 | my ($source, $captures) = @_; |
efb592ef |
153 | |
a30f41f7 |
154 | if ($ENV{EVAL_CLOSURE_PRINT_SOURCE}) { |
f3c27658 |
155 | _dump_source(_make_compiler_source(@_)); |
a30f41f7 |
156 | } |
efb592ef |
157 | |
53b0abc5 |
158 | my @capture_keys = sort keys %$captures; |
447800b5 |
159 | my ($compiler, $e) = _make_compiler($source, @capture_keys); |
f3c27658 |
160 | my $code; |
161 | if (defined $compiler) { |
447800b5 |
162 | $code = $compiler->(@$captures{@capture_keys}); |
f3c27658 |
163 | } |
26eb0e7a |
164 | |
b86710e9 |
165 | if (defined($code) && (!ref($code) || ref($code) ne 'CODE')) { |
3eb05ecb |
166 | $e = "The 'source' parameter must return a subroutine reference, " |
167 | . "not $code"; |
26eb0e7a |
168 | undef $code; |
26eb0e7a |
169 | } |
170 | |
18b5b42a |
171 | return ($code, $e); |
efb592ef |
172 | } |
173 | |
f3c27658 |
174 | sub _make_compiler { |
175 | local $@; |
176 | local $SIG{__DIE__}; |
177 | my $compiler = eval _make_compiler_source(@_); |
178 | my $e = $@; |
179 | return ($compiler, $e); |
180 | } |
61717119 |
181 | memoize('_make_compiler'); |
f3c27658 |
182 | |
183 | sub _make_compiler_source { |
447800b5 |
184 | my ($source, @capture_keys) = @_; |
f3c27658 |
185 | my $i = 0; |
efb592ef |
186 | return join "\n", ( |
f3c27658 |
187 | 'sub {', |
efb592ef |
188 | (map { |
f3c27658 |
189 | 'my ' . $_ . ' = ' . substr($_, 0, 1) . '{$_[' . $i++ . ']};' |
447800b5 |
190 | } @capture_keys), |
efb592ef |
191 | $source, |
f3c27658 |
192 | '}', |
efb592ef |
193 | ); |
194 | } |
195 | |
196 | sub _dump_source { |
409b8f41 |
197 | my ($source) = @_; |
efb592ef |
198 | |
199 | my $output; |
200 | if (try { require Perl::Tidy }) { |
201 | Perl::Tidy::perltidy( |
202 | source => \$source, |
203 | destination => \$output, |
204 | ); |
205 | } |
206 | else { |
207 | $output = $source; |
208 | } |
209 | |
409b8f41 |
210 | warn "$output\n"; |
efb592ef |
211 | } |
212 | |
ed9a00ae |
213 | =head1 BUGS |
214 | |
215 | No known bugs. |
216 | |
217 | Please report any bugs through RT: email |
218 | C<bug-eval-closure at rt.cpan.org>, or browse to |
219 | L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure>. |
220 | |
221 | =head1 SEE ALSO |
222 | |
223 | =over 4 |
224 | |
225 | =item * L<Class::MOP::Method::Accessor> |
226 | |
227 | This module is a factoring out of code that used to live here |
228 | |
229 | =back |
230 | |
231 | =head1 SUPPORT |
232 | |
233 | You can find this documentation for this module with the perldoc command. |
234 | |
235 | perldoc Eval::Closure |
236 | |
237 | You can also look for information at: |
238 | |
239 | =over 4 |
240 | |
241 | =item * AnnoCPAN: Annotated CPAN documentation |
242 | |
243 | L<http://annocpan.org/dist/Eval-Closure> |
244 | |
245 | =item * CPAN Ratings |
246 | |
247 | L<http://cpanratings.perl.org/d/Eval-Closure> |
248 | |
249 | =item * RT: CPAN's request tracker |
250 | |
251 | L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure> |
252 | |
253 | =item * Search CPAN |
254 | |
255 | L<http://search.cpan.org/dist/Eval-Closure> |
256 | |
257 | =back |
258 | |
259 | =head1 AUTHOR |
260 | |
261 | Jesse Luehrs <doy at tozt dot net> |
262 | |
263 | Based on code from L<Class::MOP::Method::Accessor>, by Stevan Little and the |
264 | Moose Cabal. |
265 | |
266 | =cut |
267 | |
efb592ef |
268 | 1; |