Add a source locator that can detect "autoload" and "autoload-dev" when given a composer schema definition from either a composer.json or a composer.lock

[Ocramius]

Given a composer.json-alike array and a string $sourcesBasePath

['autoload' => [
    'psr-0' => [/* ... */],
    'psr-4' => [/* ... */],
    'classmap' => [/* ... */],
    'files' => [/* ... */],
    'exclude-from-classmap' => [/* ... */],
]];

we can generate a SourceLocator instance that closes around it.

[Ocramius]

Relevant: Roave/BackwardCompatibilityCheck#97

[Ocramius]

After working on Roave/BackwardCompatibilityCheck#97 and Roave/BackwardCompatibilityCheck#102, I noticed a massive performance slowdown in the discovery of symbols by name. This is because BetterReflection (by default) iterates over each source locator, asking for known symbols.

If we implement a PSR-0, PSR-4, and generally a composer.json-based source locator, we can make the lookups for existing classes direct hits, instead of recursive (directory) iterator operations, hence speeding up the entire process from O(n) to O(1) when the location of a class is known.

[Ocramius]

An example implementation is available at https://github.com/Roave/BackwardCompatibilityCheck/blob/a239f81bdfb8c68b8cf6c064b75bc13d77d789b7/src/LocateSources/LocateSourcesViaComposerJson.php#L63-L96 - it works, but it is slow as heck due to it being an AggregateSourceLocator that contains all files in the discovered paths (and therefore iterates over existing files rather than performing direct hits)

[moufmouf]

I haven't the time to work on this directly, but just wanted to mention I did something quite similar:

• thecodingmachine/classname-mapper => given a composer.json file and a class name will give you the list of possible file paths. With a few changes to read composer.lock instead of composer.json and that should do the trick.
• thecodingmachine/class-explorer (WIP): for a given namespace, will scan all file names and return possibles classes (it does not read the files so it is pretty fast, but can return false positives)

[prisis]

I have something like this https://github.com/narrowspark/automatic/blob/master/src/Common/ClassFinder.php, so maybe I can just port it

[asgrim]

@Ocramius does the ComposerSourceLocator do this anyway...?

$composer = require "vendor/autoload.php';
$locator = new ComposerSourceLoucater($composer, $astLocator);

[Ocramius]

As discussed in person, the ComposerSourceLocator uses an autoloader for that, and that means creating a real ClassLoader:

BetterReflection/src/SourceLocator/Type/ComposerSourceLocator.php

Line 7 in f54261a

use Composer\Autoload\ClassLoader;

I could probably try using it, but the code is not side-effect-free, sadly:

https://github.com/composer/composer/blob/568081f9b68b9f7191a90d8ff9289913ee6e0be8/src/Composer/Autoload/ClassLoader.php#L335

[Ocramius]

Note that following monstrosity won't be implemented for now:

    'exclude-from-classmap' => [/* ... */],