/ 
Data-Sah-0.18
River stage three • 442 direct dependents • 699 total dependents
/ Data::Sah::Compiler::Prog

NAME

Data::Sah::Compiler::Prog - Base class for programming language compilers

VERSION

version 0.18

SYNOPSIS

DESCRIPTION

This class is derived from Data::Sah::Compiler. It is used as base class for compilers which compile schemas into code (validator) in several programming languages, Perl (Data::Sah::Compiler::perl) and JavaScript (Data::Sah::Compiler::js) being two of them. (Other similar programming languages like PHP and Ruby might also be supported later on if needed).

Compilers using this base class are flexible in the kind of code they produce:

  • configurable validator return type

    Can generate validator that returns a simple bool result, str, or full data structure (containing errors, warnings, and potentially other information).

  • configurable data term

    For flexibility in combining the validator code with other code, e.g. putting inside subroutine wrapper (see Perinci::Sub::Wrapper) or directly embedded to your source code (see Dist::Zilla::Plugin::Rinci::Validate).

HOW IT WORKS

The compiler generates code in the following form:

EXPR && EXPR2 && ...

where EXPR can be a single expression or multiple expressions joined by the list operator (which Perl and JavaScript support). Each EXPR is typically generated out of a single schema clause. Some pseudo-example of generated JavaScript code:

(data >= 0)  # from clause: min => 0
&&
(data <= 10) # from clause: max => 10

Another example, a fuller translation of schema [int => {min=>0, max=>10}] to Perl, returning string result (error message) instead of boolean:

# from clause: req => 0
!defined($data) ? 1 : (

    # type check
    ($data =~ /^[+-]?\d+$/ ? 1 : ($err //= "Data is not an integer", 0))

    &&

    # from clause: min => 0
    ($data >=  0 ? 1 : ($err //= "Must be at least 0", 0))

    &&

    # from clause: max => 10
    ($data <= 10 ? 1 : ($err //= "Must be at most 10", 0))

)

The final validator code will add enclosing subroutine and variable declaration, loading of modules, etc.

Note: Current assumptions/hard-coded things for the supported languages: ternary operator (? :), semicolon as statement separator.

ATTRIBUTES

These usually need not be set/changed by users.

hc => OBJ

Instance of Data::Sah::Compiler::human, to generate error messages.

comment_style => STR

Specify how comments are written in the target language. Either 'cpp' (// comment), 'shell' (# comment), 'c' (/* comment */), or 'ini' (; comment). Each programming language subclass will set this, for example, the perl compiler sets this to 'shell' while js sets this to 'cpp'.

var_sigil => STR

concat_op => STR

logical_and_op => STR

logical_not_op => STR

METHODS

new() => OBJ

$c->compile(%args) => RESULT

Aside from base class' arguments, this class supports these arguments (suffix * denotes required argument):

  • data_term => STR

    A variable name or an expression in the target language that contains the data, defaults to var_sigil + name if not specified.

  • data_term_is_lvalue => BOOL (default: 1)

    Whether data_term can be assigned to.

  • tmp_data_name => STR

    Normally need not be set manually, as it will be set to "tmp_" . data_name. Used to store temporary data during clause evaluation.

  • tmp_data_term => STR

    Normally need not be set manually, as it will be set to var_sigil . tmp_data_name. Used to store temporary data during clause evaluation. For example, in JavaScript, the 'int' and 'float' type pass strings in the type check. But for further checking with the clauses (like 'min', 'max', 'divisible_by') the string data needs to be converted to number first. Likewise with prefiltering. This variable holds the temporary value. The clauses compare against this value. At the end of clauses, the original data_term is restored. So the output validator code for schema [int => min => 1] will look something like:

    // type check 'int'
type(data)=='number' && Math.round(data)==data || parseInt(data)==data)

&&

// convert to number
(tmp_data = type(data)=='number' ? data : parseFloat(data), true)

&&

// check clause 'min'
(tmp_data >= 1)

  • err_term => STR

    A variable name or lvalue expression to store error message(s), defaults to var_sigil + err_NAME (e.g. $err_data in the Perl compiler).

  • var_prefix => STR (default: _sahv_)

    Prefix for variables declared by generated code.

  • sub_prefix => STR (default: _sahs_)

    Prefix for subroutines declared by generated code.

  • code_type => STR (default: validator)

    The kind of code to generate. For now the only valid (and default) value is 'validator'. Compiler can perhaps generate other kinds of code in the future.

  • return_type => STR (default: bool)

    Specify what kind of return value the generated code should produce. Either bool, str, or full.

    bool means generated validator code should just return true/false depending on whether validation succeeds/fails.

    str means validation should return an error message string (the first one encountered) if validation fails and an empty string/undef if validation succeeds.

    full means validation should return a full data structure. From this structure you can check whether validation succeeds, retrieve all the collected errors/warnings, etc.

  • debug => BOOL (default: 0)

    This is a general debugging option which should turn on all debugging-related options, e.g. produce more comments in the generated code, etc. Each compiler might have more specific debugging options.

  • debug_log => BOOL (default: 0)

    Whether to add logging to generated code.

  • comment => BOOL (default: 1)

    If set to false, generated code will be devoid of comments.

Compilation data

This subclass adds the following compilation data ($cd).

Keys which contain compilation state:

  • data_term => ARRAY

    Input data term. Set to $cd->{args}{data_term} or a temporary variable (if $cd->{args}{data_term_is_lvalue} is false). Hooks should use this instead of $cd->{args}{data_term} directly, because aside from the aforementioned temporary variable, data term can also change, for example if default.temp or prefilters.temp attribute is set, where generated code will operate on another temporary variable to avoid modifying the original data. Or when .input attribute is set, where generated code will operate on variable other than data.

Keys which contain compilation result:

  • modules => ARRAY

    List of module names that are required by the code, e.g. ["Scalar::Utils", "List::Util"]).

  • subs => ARRAY

    Contains pairs of subroutine names and definition code string, e.g. [ [_sahs_zero => 'sub _sahs_zero { $_[0] == 0 }'], [_sahs_nonzero => 'sub _sah_s_nonzero { $_[0] != 0 }'] ]. For flexibility, you'll need to do this bit of arranging yourself to get the final usable code you can compile in your chosen programming language.

  • vars => HASH

$c->comment($cd, @args) => STR

Generate a comment. For example, in perl compiler:

$c->comment($cd, "123"); # -> "# 123\n"

Will return an empty string if compile argument comment is set to false.

INTERNAL VARIABLES IN THE GENERATED CODE

The generated code maintains the following variables. _sahv_ prefix stands for "Sah validator", it is used to minimize clash with data_term.

  • _sahv_dpath => ARRAY

    Analogous to spath in compilation data, this variable stands for "data path" and is used to track location within data. If a clause is checking each element of an array (like the 'each_elem' or 'elems' array clause), this variable will be adjusted accordingly. Error messages thus can be more informative by pointing more exactly where in the data the problem lies.

  • tmp_data_term => ANY

    As explained in the compile() method, this is used to store temporary value when checking against clauses.

  • _sahv_stack => ARRAY

    This variable is used to store validation result of subdata. It is only used if the validator is returning a string or full structure, not a single boolean value. See Data::Sah::Compiler::js::TH::hash for an example.

  • _sahv_x

    Usually used as temporary variable in short, anonymous functions.

AUTHOR

Steven Haryanto <stevenharyanto@gmail.com>

COPYRIGHT AND LICENSE

This software is copyright (c) 2013 by Steven Haryanto.

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