NAME Data::Sah::Coerce - Coercion rules for Data::Sah VERSION This document describes version 0.030 of Data::Sah::Coerce (from Perl distribution Data-Sah-Coerce), released on 2018-12-16. SYNOPSIS use Data::Sah::Coerce qw(gen_coercer); # a utility routine: gen_coercer my $c = gen_coercer( type => 'date', coerce_to => 'DateTime', coerce_rules => ['str_alami'], # explicitly enable a rule, etc # return_type => 'str+val', # default is 'val' ); my $val = $c->(123); # unchanged, 123 my $val = $c->(1463307881); # becomes a DateTime object my $val = $c->("2016-05-15"); # becomes a DateTime object my $val = $c->("2016foo"); # unchanged, "2016foo" DESCRIPTION This distribution contains a standard set of coercion rules for Data::Sah. It is separated from the "Data-Sah" distribution and can be used independently. A coercion rule is put in "Data::Sah::Coerce::$COMPILER::$TARGET_TYPE::$SOURCE_TYPE_AND_EXTRA_DESC RIPTION" module, for example: Data::Sah::Coerce::perl::date::float_epoch for converting date from integer (Unix epoch) or Data::Sah::Coerce::perl::date::str_iso8601 for converting date from ISO8601 strings like "2016-05-15". Basically, a coercion rule will provide an expression ("expr_match") that evaluates to true when data can be coerced, and an expression ("expr_coerce") to actually coerce/convert data to the target type. This rule can be combined with other rules to form the final coercion code. The module must contain "meta" subroutine which must return a hashref that has the following keys ("*" marks that the key is required): * v* => int (default: 1) Metadata specification version. Currently at 3. History: bumped from 2 to 3 to allow coercion expression to return error message explaining why coercion fails. The "might_die" metadata property is replaced with "might_fail". When "might_fail" is set to true, "expr_coerce" must return array containing error message and coerced data, instead of just coerced data. History: Bumped from 1 to 2 to exclude old module names. * enable_by_default* => bool Whether the rule should be used by default. Some rules might be useful in certain situations only and can set this key's value to 0. To explicitly enable a disabled-by-default rule or explicitly disable an enabled-by-default rule, a Sah schema can set the attribute "x.coerce_rules" or "x.perl.coerce_rules" to something like "["!str_iso8601", "str_alami"]" (this means to exclude the "str_iso8601" rule but enable the "str_alami" rule). * might_fail => bool (default: 0) Whether coercion might fail, e.g. because of invalid input. If set to 1, "expr_coerce" key that the "coerce()" routine returns must be an expression that returns an array (envelope) of "(error_msg, data)" instead of just coerced data. Error message should be a string that is set when coercion fails and explains why. Otherwise, if coercion succeeds, the string should be set to undefined value. An example of a rule like this is coercing from string in the form of "YYYY-MM-DD" to a DateTime object. The rule might match any string in the form of "/\A(\d{4})-(\d{2})-(\d{2})\z/" while it might not be a valid date. * prio => int (0-100, default: 50) This is to regulate the ordering of rules. The higher the number, the lower the priority (meaning the rule will be put further back). Rules that are computationally more expensive and/or match more broadly in general should be put further back (lower priority, higher number). * precludes => array of (str|re) List the other rules or rule patterns that are precluded by this rule. Rules that are mutually exclusive or pure alternatives to one another (e.g. date coercien rules str_alami vs str_alami both parse natural language date string; there is usually little to none of usefulness in using both; besides, both rules match all string and dies when failing to parse the string. So in "str_natural" rule, you'll find this metadata: precludes => [qr/\Astr_alami(_.+)?\z/] and in "str_alami" rule you'll find this metadata: precludes => [qr/\Astr_alami(_.+)?\z/, 'str_natural'] Note that the "str_alami" rule also precludes other "str_alami_*" rules (like "str_alami_en" and "str_alami_id"). Also note that rules which are specifically requested to be used (e.g. using "x.perl.coerce_rules" attribute in Sah schema) will still be precluded. The module must also contain "coerce" subroutine which must generate the code for coercion. The subroutine must accept a hash of arguments ("*" indicates required arguments): * data_term => str * coerce_to => str Some Sah types are "abstract" and can be represented using a choice of several actual types in the target programming language. For example, "date" can be represented in Perl as an integer (Unix epoch value), or a DateTime object, or a Time::Moment object. Not all target Sah types will need this argument. The "coerce" subroutine must return a hashref with the following keys ("*" indicates required keys): * expr_match => str Expression in the target language to test whether the data can be coerced. For example, in "Data::Sah::Coerce::perl::date::float_epoch", only integers ranging from 10^8 to 2^31 are converted into date. Non-integers or integers outside this range are not coerced. * expr_coerce => str Expression in the target language to actually convert data to the target type. * modules => hash A list of modules required by the expressions. Basically, the "coerce" subroutine must generates a code that accepts a non-undef data and must convert this data to the desired type/format under the right condition. The code to match the right condition must be put in "expr_match" and the code to convert data must be put in "expr_coerce". Program/library that uses Data::Sah::Coerce can collect rules from the rule modules then compose them into the final code, something like (in pseudocode): if (data is undef) { return undef; } elsif (data matches expr-match-from-rule1) { return expr-coerce-from-rule1; } elsif (data matches expr-match-from-rule2) { return expr-coerce-from-rule1; ... } else { # does not match any expr-match return original data; } VARIABLES $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::Coerce=gen_coercer -E'my $c = gen_coercer(...)' FUNCTIONS gen_coercer Usage: gen_coercer() -> 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. No arguments. Return value: (any) ENVIRONMENT LOG_SAH_COERCER_CODE => bool Set default for $Log_Coercer_Code. HOMEPAGE Please visit the project's homepage at . SOURCE Source repository is at . BUGS Please report any bugs or feature requests on the bugtracker website When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature. SEE ALSO Data::Sah Data::Sah::CoerceJS App::SahUtils, including coerce-with-sah to conveniently test coercion from the command-line. AUTHOR perlancar COPYRIGHT AND LICENSE This software is copyright (c) 2018, 2017, 2016 by perlancar@cpan.org. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.