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Sah::Schema::array_from_json - Array, coercible from JSON string


This document describes version 0.007 of Sah::Schema::array_from_json (from Perl distribution Sah-Schemas-JSON), released on 2022-11-15.


Sample data and validation results against this schema

 ""  # INVALID (Empty string is not a valid JSON)

 1  # INVALID (Valid JSON but not an array)

 "{}"  # INVALID (Valid JSON but not an array)

 []  # valid (Already an array)

 {}  # INVALID (Not an array)

 "foo"  # INVALID (Not a valid JSON literal)

 "[1,2,3,{}]"  # valid, becomes [1,2,3,{}]

 "[1,2"  # INVALID (Missing closing square bracket)

 "[1,2,]"  # INVALID (Dangling comma)

Using with Data::Sah

To check data against this schema (requires Data::Sah):

 use Data::Sah qw(gen_validator);
 my $validator = gen_validator("array_from_json*");
 say $validator->($data) ? "valid" : "INVALID!";

The above schema returns a boolean result (true if data is valid, false if otherwise). To return an error message string instead (empty string if data is valid, a non-empty error message otherwise):

 my $validator = gen_validator("array_from_json", {return_type=>'str_errmsg'});
 my $errmsg = $validator->($data);
 # a sample valid data
 $data = [];
 my $errmsg = $validator->($data); # => ""
 # a sample invalid data
 $data = 1;
 my $errmsg = $validator->($data); # => "Not of type array"

Often a schema has coercion rule or default value, so after validation the validated value is different. To return the validated (set-as-default, coerced, prefiltered) value:

 my $validator = gen_validator("array_from_json", {return_type=>'str_errmsg+val'});
 my $res = $validator->($data); # [$errmsg, $validated_val]
 # a sample valid data
 $data = [];
 my $res = $validator->($data); # => ["",[]]
 # a sample invalid data
 $data = 1;
 my $res = $validator->($data); # => ["Not of type array",1]

Data::Sah can also create validator that returns a hash of detailed error message. Data::Sah can even create validator that targets other language, like JavaScript, from the same schema. Other things Data::Sah can do: show source code for validator, generate a validator code with debug comments and/or log statements, generate human text from schema. See its documentation for more details.

Using with Params::Sah

To validate function parameters against this schema (requires Params::Sah):

 use Params::Sah qw(gen_validator);

 sub myfunc {
     my @args = @_;
     state $validator = gen_validator("array_from_json*");

Using with Perinci::CmdLine::Lite

To specify schema in Rinci function metadata and use the metadata with Perinci::CmdLine (Perinci::CmdLine::Lite) to create a CLI:

 # in lib/
 our %SPEC;
 $SPEC{myfunc} = {
     v => 1.1,
     summary => 'Routine to do blah ...',
     args => {
         arg1 => {
             summary => 'The blah blah argument',
             schema => ['array_from_json*'],
 sub myfunc {
     my %args = @_;

 # in
 use Perinci::CmdLine::Any;

 # in command-line
 % ./ --help
 myapp - Routine to do blah ...

 % ./ --version

 % ./ --arg1 ...

Using with Type::Tiny

To create a type constraint and type library from a schema:

 package My::Types {
     use Type::Library -base;
     use Type::FromSah qw( sah2type );

         sah2type('$sch_name*', name=>'ArrayFromJson')

 use My::Types qw(ArrayFromJson);


You can use this schema if you want to accept an array, but if user supplies a string e.g. in a command-line script as command-line argument or option, the string will be coerced into array if the string contains a JSON-encoded array. Data will not be valid if the string does not contain valid JSON.

Note that array data is accepted, unlike the json_str::array schema which only accepts JSON-encoded array in string form.


Please visit the project's homepage at


Source repository is at


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, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2022, 2021 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.


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.