Re^2: Importing multiple %EXPORT

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Re^3: Importing multiple %EXPORT_TAGS by jcb (Parson) on Dec 28, 2020 at 01:57 UTC
If I read that correctly, you might want to check your namespace after importing `:all`... The `_add_private` sub will be called while initializing `%EXPORT_TAGS`, and it modifies `@EXPORT_OK`, which is also used to define (by reference) the `:all` tag. Data::Dumper should illustrate this if asked to dump the `%EXPORT_TAGS` hash. If you still want this, I suggest: (untested) `# ... our %EXPORT_TAGS = ( all => [@EXPORT_OK], ); $EXPORT_TAGS{private} = _add_private(); # ...` [download] The `%EXPORT_TAGS` initialization is split into two statements to ensure a sequence point and avoid a possible undefined evaluation order. This ensures that the initial `@EXPORT_OK` is copied into a new array before `_add_private` modifies its contents.	[reply] [d/l] [select]
Re^4: Importing multiple %EXPORT_TAGS by stevieb (Canon) on Dec 28, 2020 at 04:44 UTC
Great catch! However, the separation isn't needed. As soon as I saw you put the `EXPORT_OK` into an anonymous array, changed from the taking of the reference as I had it, I realized that's all that was needed. So `all` now instead of being a reference to the array, it's a reference to a copy of it: `our %EXPORT_TAGS = ( all => [ @EXPORT_OK ], private => _export_private(), ); sub _export_private { push @EXPORT_OK, @EXPORT_PRIVATE; return \@EXPORT_OK; }` [download] Output: $VAR1 = { 'private' => [ 'add_bugtracker', 'add_repository', 'changes', 'changes_bump', 'changes_date', 'ci_badges', 'ci_github', 'git_ignore', 'init', 'make_test', 'manifest_skip', 'move_distribution_files', 'remove_unwanted_files', 'version_bump', 'version_info', '_git_commit', '_git_push', '_validate_git' ], 'all' => [ 'add_bugtracker', 'add_repository', 'changes', 'changes_bump', 'changes_date', 'ci_badges', 'ci_github', 'git_ignore', 'init', 'make_test', 'manifest_skip', 'move_distribution_files', 'remove_unwanted_files', 'version_bump' 'version_info', ] }; [download]	[reply] [d/l] [select]
Re^5: Importing multiple %EXPORT_TAGS by jcb (Parson) on Dec 29, 2020 at 03:52 UTC
I am fairly sure the separation is needed, unless you can point to documentation somewhere that says the values used to initialize a hash will always be evaluated left-to-right. Otherwise, your code may work now, but is relying on undefined behavior and may stop working in a future version of perl. The problem is that `_export_private` modifies `@EXPORT_OK`, so the order in which `[@EXPORT_OK]` and `_export_private()` are evaluated matters. If the list values are evaluated right-to-left in some future version of perl, you will be right back where you were, as the internal functions will be added to `@EXPORT_OK` just before the array is copied for the `:all` tag.	[reply] [d/l] [select]

If I read that correctly, you might want to check your namespace after importing :all...

The _add_private sub will be called while initializing %EXPORT_TAGS, and it modifies @EXPORT_OK, which is also used to define (by reference) the :all tag. Data::Dumper should illustrate this if asked to dump the %EXPORT_TAGS hash.

If you still want this, I suggest: (untested)

# ...
our %EXPORT_TAGS = (
    all => [@EXPORT_OK],
);
$EXPORT_TAGS{private} = _add_private();
# ...
[download]

The %EXPORT_TAGS initialization is split into two statements to ensure a sequence point and avoid a possible undefined evaluation order. This ensures that the initial @EXPORT_OK is copied into a new array before _add_private modifies its contents.

[reply]
[d/l]
[select]

Great catch!

However, the separation isn't needed. As soon as I saw you put the EXPORT_OK into an anonymous array, changed from the taking of the reference as I had it, I realized that's all that was needed. So all now instead of being a reference to the array, it's a reference to a copy of it:

our %EXPORT_TAGS = (
    all     => [ @EXPORT_OK ],
    private => _export_private(),
);

sub _export_private {
    push @EXPORT_OK, @EXPORT_PRIVATE;
    return \@EXPORT_OK;
}
[download]

Output:

$VAR1 = {
          'private' => [
                         'add_bugtracker',
                         'add_repository',
                         'changes',
                         'changes_bump',
                         'changes_date',
                         'ci_badges',
                         'ci_github',
                         'git_ignore',
                         'init',
                         'make_test',
                         'manifest_skip',
                         'move_distribution_files',
                         'remove_unwanted_files',
                         'version_bump',
                         'version_info',
                         '_git_commit',
                         '_git_push',
                         '_validate_git'
                       ],
          'all' => [
                     'add_bugtracker',
                     'add_repository',
                     'changes',
                     'changes_bump',
                     'changes_date',
                     'ci_badges',
                     'ci_github',
                     'git_ignore',
                     'init',
                     'make_test',
                     'manifest_skip',
                     'move_distribution_files',
                     'remove_unwanted_files',
                     'version_bump'
                     'version_info',
                   ]
        };
[download]

[reply]
[d/l]
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I am fairly sure the separation is needed, unless you can point to documentation somewhere that says the values used to initialize a hash will always be evaluated left-to-right. Otherwise, your code may work now, but is relying on undefined behavior and may stop working in a future version of perl.

The problem is that _export_private modifies @EXPORT_OK, so the order in which [@EXPORT_OK] and _export_private() are evaluated matters. If the list values are evaluated right-to-left in some future version of perl, you will be right back where you were, as the internal functions will be added to @EXPORT_OK just before the array is copied for the :all tag.

[reply]
[d/l]
[select]