Data::Sah::CoerceJS - Generate coercer code


This document describes version 0.052 of Data::Sah::CoerceJS (from Perl distribution Data-Sah-Coerce), released on 2021-11-28.


 use Data::Sah::CoerceJS qw(gen_coercer);

 # use as you would use Data::Sah::Coerce


This module is just like Data::Sah::Coerce except that it uses JavaScript coercion rule modules.


$Log_Coercer_Code => bool (default: from ENV or 0)

If set to true, will log the generated coercer code (currently using Log::ger at trace level). To see the log message, e.g. to the screen, you can use something like:

 % TRACE=1 perl -MLog::ger::LevelFromEnv -MLog::ger::Output=Screen \
     -MData::Sah::CoerceJS=gen_coercer -E'my $c = gen_coercer(...)'




 gen_coercer(%args) -> any

Generate coercer code.

This is mostly for testing. Normally the coercion rules will be used from Data::Sah.

This function is not exported by default, but exportable.

Arguments ('*' denotes required arguments):

  • coerce_rules => array[str]

    A specification of coercion rules to use (or avoid).

    This setting is used to specify which coercion rules to use (or avoid) in a flexible way. Each element is a string, in the form of either NAME to mean specifically include a rule, or !NAME to exclude a rule.

    Some coercion modules are used by default, unless explicitly avoided using the '!NAME' rule.

    To not use any rules:

    To use the default rules plus R1 and R2:

     ['R1', 'R2']

    To use the default rules but not R1 and R2:

     ['!R1', '!R2']
  • coerce_to => str

    Some Sah types, like date, can be represented in a choice of types in the target language. For example, in Perl you can store it as a floating number a.k.a. float(epoch), or as a DateTime object, or Time::Moment object. Storing in DateTime can be convenient for date manipulation but requires an overhead of loading the module and storing in a bulky format. The choice is yours to make, via this setting.

  • return_type => str (default: "val")

    val means the coercer will return the input (possibly) coerced or undef if coercion fails.

    bool_coerced+val means the coercer will return a 2-element array. The first element is a bool value set to 1 if coercion has been performed or 0 if otherwise. The second element is the (possibly) coerced input.

    bool_coerced+str_errmsg+val means the coercer will return a 3-element array. The first element is a bool value set to 1 if coercion has been performed or 0 if otherwise. The second element is the error message string which will be set if there is a failure in coercion (or undef if coercion is successful). The third element is the (possibly) coerced input.

  • source => bool

    If set to true, will return coercer source code string instead of compiled code.

  • type* => sah::type_name

Return value: (any)



Set default for $Log_Coercer_Code.


Please visit the project's homepage at


Source repository is at



App::SahUtils, including coerce-with-sah to conveniently test coercion from the command-line.


perlancar <>


To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla plugin and/or Pod::Weaver::Plugin. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2021, 2020, 2019, 2018, 2017, 2016 by perlancar <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


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