Rename binding types to "contracts"

[webmozart]

We currently use the term "binding type" for specifying the common denominator between modules providing "things" (resources, classes, user-defined) and modules consuming (or using) those things. That term unfortunately is quite abstract and not intuitive to grasp.

To borrow a term from software architecture, I would like to propose changing that term to "contract". Modules can define contracts and use any "thing" that satisfies that contract. Other modules can provide things satisfying the contract.

A contract is made up of three properties:

• its globally unique name
• the type of the things the contract expects ("resource", "class", user-defined)
• optional: named parameters

The definition of contracts would look like this:

{
    "contracts": {
        "Vendor\\PluginInterface": {
            "require": "class",
            "parameters": {
                "foo": {
                    "default": "bar"
                }
            }
        },
        "vendor/translations-yml": "resource"
    }
}

When a module provides "things" satisfying the contract, that looks like this:

{
    "provide": {
        "Acme\\PluginA": "Vendor\\PluginInterface",
        "Acme\\PluginB": {
            "contract": "Vendor\\PluginInterface",
            "parameters": {
                "foo": "baz"
            }
        },
        "/acme/module/trans/*.yml": "vendor/translations-yml"
    }
}

I quite like that changed naming and think it is much easier to understand without explaining as much as we currently have to explain. If there are no major concerns, I'd like to tackle this change with beta12.

[tgalopin]

After seeing it written, it's really a good name :) .

[webmozart]

In a later step, we can also add "constraints" to those contracts that can be defined for each "type". Example constraint for the "resource" type:

{
    "contracts": {
        "vendor/translations-yml": {
            "type": "resource",
            "constraints": {
                "extension": ".yml"
            }
        }
    }
}

The goal here is to document and enforce the specific constraints that the provided "things" must fulfill.

[tgalopin]

What about an array of globs for constraints? It seems more powerful than a specific "extension" key.

[webmozart]

Sure :) we can discuss this when we get there.