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https://github.com/marcioAlmada/yay
Yay is a high level PHP preprocessor
https://github.com/marcioAlmada/yay
macro-dsl macros parser-combinators preprocessor
Last synced: 9 days ago
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Yay is a high level PHP preprocessor
- Host: GitHub
- URL: https://github.com/marcioAlmada/yay
- Owner: marcioAlmada
- License: mit
- Created: 2015-08-20T01:30:54.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2024-01-31T15:54:40.000Z (10 months ago)
- Last Synced: 2024-10-16T08:49:34.221Z (28 days ago)
- Topics: macro-dsl, macros, parser-combinators, preprocessor
- Language: PHP
- Homepage: https://github.com/marcioAlmada/yay
- Size: 495 KB
- Stars: 572
- Watchers: 23
- Forks: 35
- Open Issues: 13
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# YAY!
[](https://travis-ci.org/marcioAlmada/yay)
[](https://coveralls.io/github/marcioAlmada/yay?branch=travis)
[](https://packagist.org/packages/yay/yay)
[](https://gitter.im/marcioAlmada/yay?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
[](https://packagist.org/packages/yay/yay)
**YAY!** is a high level parser combinator based PHP preprocessor that allows anyone to augment PHP with PHP :boom:
This means that language features could be distributed as composer packages (as long as the macro based implementations
can be expressed in pure PHP code, and the implementation is fast enough).
[Roadmap](https://github.com/marcioAlmada/yay/issues/3).
## Set Up
```bash
composer require yay/yay:dev-master
```
## Usage
### Command Line
```
yay some/file/with/macros.php >> target/file.php
```
### Runtime Mode
The "runtime" mode is W.I.P and will use stream wrappers along with composer integration in order
to preprocess every file that gets included. It may have some opcache/cache support, so files will be
only preprocessed/expanded once and when needed.
See feature progress at issue [#11](https://github.com/marcioAlmada/yay/issues/11).
## How it works
### Very Simple Example
Every macro consist of a matcher and an expander that when executed allows you to augment PHP.
Consider the simplest example possible:
```php
$(macro :unsafe) { $ } >> { $this } // this shorthand
```
The macro is basically expanding a literal `$` token to `$this`. The following code would expand to:
```php
// source | // expansion
class Foo { | class Foo {
protected $a = 1, $b = 2, $c = 3; | protected $a = 1, $b = 2, $c = 3;
|
function getProduct(): int { | function getProduct(): int {
return $->a * $->b * $->c; | return $this->a * $this->b *$this->c;
} | }
} | }
```
> Notice that the `:unsafe` tag is necessary to avoid macro hygiene on `$this` expansion.
This macro is actually very naive, a more producion ready version would be:
```php
$(macro :unsafe){
$ // litterally matches '$'
// but not followed by:
$(not(token(T_VARIABLE))) // avoids var var false positives such as '$$foo'
$(not(token('{'))) // avoids false positives such as '${foo}'
} >> {
$this
}
```
### Simple Example
Apart from literal characher sequences, it's also possible to match specific token types using the token matcher in
the form of `$(TOKEN_TYPE as label)`.
The following macro matches token sequences like `__swap($x, $y)` or `__swap($foo, $bar)`:
```php
$(macro) {
__swap ( $(T_VARIABLE as A) , $(T_VARIABLE as B) )
} >> {
(list($(A), $(B)) = [$(B), $(A)])
}
```
The expansion should be pretty obvious:
```php
// source | // expansion
__swap($foo, $bar); | (list($foo, $bar) = [$bar, $foo]);
```
### Another Simple Example
To implement `unless` we need to match the literal `unless` keyword followed by a layer of tokens between parentheses
`(...)` and a block of code `{...}`. Fortunately, the macro DSL has a very straightforward layer matching construct:
```php
$(macro) {
unless ($(layer() as expression)) { $(layer() as body) }
} >> {
if (! ($(expression))) {
$(body)
}
}
```
The macro in action:
```php
// source | // expansion
unless ($x === 1) { | if (! ($x === 1)) {
echo "\$x is not 1"; | echo "\$x is not 1";
} | }
```
> PS: Please don't implement "unless". This is here just for didactic reasons.
### Advanced Example
A more complex example could be porting enums from the future to PHP with a syntax like:
```php
enum Fruits {
Apple,
Orange
}
var_dump(\Fruits::Orange <=> \Fruits::Apple);
```
So, syntactically, enums are declared with the literal `enum` word followed by a `T_STRING` and a comma
separated list of identifiers withing braces such as `{A, B, C}`.
YAY uses parser combinators internally for everything and these more high level parsers are fully
exposed on macro declarations. Our enum macro will need high level matchers like `ls()` and `label()`
combined to match the desired syntax, like so:
```php
$(macro) {
enum $(T_STRING as name) {
$(
// ls() matches a delimited list
// in this case a list of label() delimited by ',' such as `foo, bar, baz`
ls
(
label() as field
,
token(',')
)
as fields
)
}
} >> {
"it works";
}
```
The macro is already capable to match the enum syntax:
```php
// source // expansion
enum Order {ASC, DESC}; | "it works";
```
I won't explain how enums are implemented, you can read the [RFC](https://wiki.php.net/rfc/enum) if you wish
and then see how the expansion below works:
```php
// things here would normally be under a namespace, but since we want a concise example...
interface Enum
{
}
function enum_field_or_class_constant(string $class, string $field)
{
return (\in_array(\Enum::class, \class_implements($class)) ? $class::$field() : \constant("{$class}::{$field}"));
}
$(macro :unsafe) {
// the enum declaration
enum $(T_STRING as name) {
$(
ls
(
label() as field
,
token(',')
)
as fields
)
}
} >> {
class $(name) implements Enum {
private static $registry;
private function __construct() {}
static function __callStatic(string $type, array $args) : self {
if(! self::$registry) {
self::$registry = new \stdclass;
$(fields ... {
self::$registry->$(field) = new class extends $(name) {};
})
}
if (isset(self::$registry->$type)) return self::$registry->$type;
throw new \Exception(sprintf('Undefined enum type %s->%s', __CLASS__, $type));
}
}
}
$(macro) {
$(
// sequence that matches the enum field access syntax:
chain(
ns() as class, // matches a namespace
token(T_DOUBLE_COLON), // matches T_DOUBLE_COLON used for static access
not(class), // avoids matching `Foo::class`, class resolution syntax
label() as field, // matches the enum field name
not(token('(')) // avoids matching static method calls such as `Foo::bar()`
)
)
} >> {
\enum_field_or_class_constant($(class)::class, $$(stringify($(field))))
}
```
> More examples within the phpt tests folder https://github.com/marcioAlmada/yay/tree/master/tests/phpt
# FAQ
> Why "YAY!"?
\- PHP with feature "x": yay or nay? :wink:
> Where is the documentation?
A cookbook is on the making
> Why are you working on this?
Because it's being fun. It may become useful. [Because we can™](https://github.com/haskellcamargo/because-we-can).
# Conclusion
For now this is an experiment about how to build a high level preprocessor DSL using parser combinators
on a languages like PHP. Why?
PHP is very far from being [homoiconic](https://en.wikipedia.org/wiki/Homoiconicity) and therefore requires
complex deterministic parsing and a big AST implementation with a node visitor API to modify source code - and
in the end, you're not even able to easily process unknown syntax `¯\_(⊙_ʖ⊙)_/¯`.
That's why this project was born. It was also part of the challenge:
0. Create a minimalistic architecture that exposes a subset of the internal components, that power the preprocessor itself, to the user DSL.
0. Create parser combinators with decent error reporting and grammar invalidation, because of 1
## Copyright
Copyright (c) 2015-* Márcio Almada. Distributed under the terms of an MIT-style license.
See LICENSE for details.