sanmai / hoa-compiler
The Hoa\Compiler library.
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Requires
- php: >=7.0
- hoa/iterator: ^2.17
- hoa/visitor: ^2.17
Requires (Dev)
- friendsofphp/php-cs-fixer: ^2.15
- hoa/file: *
- hoa/regex: ^1
- php-coveralls/php-coveralls: ^2.1
- phpunit/phpunit: >=6.5.14
- sanmai/linter: ^0.1 || ^0.2
Suggests
- hoa/file: For getAST to work
- hoa/regex: For getAST to work
- sanmai/hoa-protocol: If you have trouble with a conflicting resolve()
Replaces
- hoa/compiler: 3.17.08.08
This package is auto-updated.
Last update: 2022-10-01 12:27:34 UTC
README
Install with:
composer require sanmai/hoa-compiler
This version of the library should be input-output-wise backward-compatible with the original package. For example, you can use this version together with jms/serializer
to avoid known problems some of the dependencies of the original package have with PHP 7.4.
BC breaking changes include:
Hoa\Exception\Exception
sub-classes are no longer thrown, please switch toHoa\Compiler\Exception
- The package itself does not depend on development time only dependencies. If you need to call
getAST()
, you need to manually installhoa/regex
andhoa/file
.
Hoa\Compiler
This library allows to manipulate LL(1) and LL(k) compiler compilers. A dedicated grammar description language is provided for the last one: the PP language.
Testing
To run all the test suites:
$ vendor/bin/hoa test:run
For more information, please read the contributor guide.
Quick usage
As a quick overview, we will look at the PP language and the LL(k) compiler compiler.
The PP language
A grammar is constituted by tokens (the units of a word) and rules (please, see the documentation for an introduction to the language theory). The PP language declares tokens with the following construction:
%token [source_namespace:]name value [-> destination_namespace]
The default namespace is default
. The value of a token is represented by a
PCRE. We can skip tokens with the %skip
construction.
As an example, we will take the simplified grammar of the JSON
language. The complete grammar is in the
hoa://Library/Json/Grammar.pp
file. Thus:
%skip space \s
// Scalars.
%token true true
%token false false
%token null null
// Strings.
%token quote_ " -> string
%token string:string [^"]+
%token string:_quote " -> default
// Objects.
%token brace_ {
%token _brace }
// Arrays.
%token bracket_ \[
%token _bracket \]
// Rest.
%token colon :
%token comma ,
%token number \d+
value:
<true> | <false> | <null> | string() | object() | array() | number()
string:
::quote_:: <string> ::_quote::
number:
<number>
#object:
::brace_:: pair() ( ::comma:: pair() )* ::_brace::
#pair:
string() ::colon:: value()
#array:
::bracket_:: value() ( ::comma:: value() )* ::_bracket::
We can see the PP constructions:
rule()
to call a rule;<token>
and::token::
to declare a token;|
for a disjunction;(…)
to group multiple declarations;e?
to say thate
is optional;e+
to say thate
can appear at least 1 time;e*
to say thate
can appear 0 or many times;e{x,y}
to say thate
can appear betweenx
andy
times;#node
to create a node the AST (resulting tree);token[i]
to unify tokens value between them.
Unification is very useful. For example, if we have a token that expresses a quote (simple or double), we could have:
%token quote "|'
%token handle \w+
string:
::quote:: <handle> ::quote::
So, the data "foo"
and 'foo'
will be valid, but also "foo'
and 'foo"
! To
avoid this, we can add a new constraint on token value by unifying them, thus:
string:
::quote[0]:: <handle> ::quote[0]::
All quote[0]
for the rule instance must have the same value. Another example
is the unification of XML tags name.
LL(k) compiler compiler
The Hoa\Compiler\Llk\Llk
class provide helpers to manipulate (load or save) a
compiler. The following code will use the previous grammar to create a compiler,
and we will parse a JSON string. If the parsing succeed, it will produce an AST
(stands for Abstract Syntax Tree) we can visit, for example to dump the AST:
// 1. Load grammar. $compiler = Hoa\Compiler\Llk\Llk::load(new Hoa\File\Read('Json.pp')); // 2. Parse a data. $ast = $compiler->parse('{"foo": true, "bar": [null, 42]}'); // 3. Dump the AST. $dump = new Hoa\Compiler\Visitor\Dump(); echo $dump->visit($ast); /** * Will output: * > #object * > > #pair * > > > token(string, foo) * > > > token(true, true) * > > #pair * > > > token(string, bar) * > > > #array * > > > > token(null, null) * > > > > token(number, 42) */
Pretty simple.
Compiler in CLI
This library proposes a script to parse and apply a visitor on a data with a
specific grammar. Very useful. Moreover, we can use pipe (because
Hoa\File\Read
—please, see the Hoa\File
library— supports 0
as
stdin
), thus:
$ echo '[1, [1, [2, 3], 5], 8]' | hoa compiler:pp Json.pp 0 --visitor dump > #array > > token(number, 1) > > #array > > > token(number, 1) > > > #array > > > > token(number, 2) > > > > token(number, 3) > > > token(number, 5) > > token(number, 8)
You can apply any visitor classes.
Errors
Errors are well-presented:
$ echo '{"foo" true}' | hoa compiler:pp Json.pp 0 --visitor dump Uncaught exception (Hoa\Compiler\Exception\UnexpectedToken): Hoa\Compiler\Llk\Parser::parse(): (0) Unexpected token "true" (true) at line 1 and column 8: {"foo" true} ↑ in hoa://Library/Compiler/Llk/Parser.php at line 1
Samplers
Some algorithms are available to generate data based on a grammar. We will give only one example with the coverage-based generation algorithm that will activate all branches and tokens in the grammar:
$sampler = new Hoa\Compiler\Llk\Sampler\Coverage( // Grammar. Hoa\Compiler\Llk\Llk::load(new Hoa\File\Read('Json.pp')), // Token sampler. new Hoa\Regex\Visitor\Isotropic(new Hoa\Math\Sampler\Random()) ); foreach ($sampler as $i => $data) { echo $i, ' => ', $data, "\n"; } /** * Will output: * 0 => true * 1 => {" )o?bz " : null , " %3W) " : [false, 130 , " 6" ] } * 2 => [{" ny " : true } ] * 3 => {" Ne;[3 " :[ true , true ] , " th: " : true," C[8} " : true } */
Research papers
- Grammar-Based Testing using Realistic Domains in PHP, presented at A-MOST 2012 (Montréal, Canada) (article, presentation, details).
License
Hoa is under the New BSD License (BSD-3-Clause). Please, see
LICENSE
for details.