composer: dependences and dependents

[block34]

$ cat .composer/config.json
{
    "repositories": {
        "a": {
            "type": "path",
            "url": "repo/a"
        },
        "b": {
            "type": "path",
            "url": "repo/b"
        },
        "c": {
            "type": "path",
            "url": "repo/c"
        }
    }
}
$ cat repo/a/composer.json
{
    "name": "my/a",
    "require": {
        "my/b": "dev-master"
    }
}
$ cat repo/b/composer.json
{
    "name": "my/b",
    "require": {
        "my/c": "dev-master"
    }
}
$ cat repo/c/composer.json
{
    "name": "my/c"
}

How do you see

my/a requires my/b
my/b requires my/c

But I wanted to know if there is a way to view *quickly* the whole structure of dependences.
Above all, I would like to know the *dependents*.

I tried like this
 

$ COMPOSER_HOME=.composer composer show -a my/b
No composer.json found in the current directory, showing available packages from a, b, c, packagist.org
name     : my/b
descrip. :
keywords :
versions : dev-master
type     : library
homepage :
source   : []
dist     : [path] repo/b 6de0f9e677dcab7051f94dbbf05893d0165bb826
names    : my/b

requires
my/c dev-master

In summary
 

$ COMPOSER_HOME=.composer composer show -a my/b \
  | grep my/
No composer.json found in the current directory, showing available packages from a, b, c, packagist.org
name     : my/b
names    : my/b
my/c dev-master

It tell me that

my/b requires my/c

but it doesn't tell me that

my/b is required from my/a (this is the thing that interests me most).

For example, if I have to remove a package (obsolete package), how can I verify that it does not have dependents?

[kicken]

Use the -t option to get a tree view of your packages.

$ composer show -t
my/a dev-master
└──my/b dev-master
   └──my/c dev-master

 

[block34]

$ COMPOSER_HOME=.composer composer show -t 
Composer could not find a composer.json file
To initialize a project, please create a composer.json file as described in the https://getcomposer.org/ "Getting Started" section
compose

 

[kicken]

As it says in the error, you need to create a composer.json file that contains the details for your project, including what it requires.  For example:

{
    "require": {
        "my/a": "dev-master"
    }
}

I suggest you read through that Getting Started section as was advised.

[block34]

Why should require my/a package?

I don't want to request/download/install anything.

Let's pretend I don't know anything.
Let's pretend I only know that the my/b package exists (I don't want to request/download/install).
Let's pretend I just want to know which packages use the my/b package.

Can it be?

[kicken]

You need to download dependencies to analyze them, since what dependencies you get can depend on the environment you're project is installed into.  So you need to start with a project that requires packages that you want.  Trying to analyze dependencies without a project doesn't really make sense.

If for some reason you don't want to make a project but want to know what packages my/b depends on, you can download my/b and run composer show -t within it's directory.  Every package is a composer project with it's own composer.json that defines it's details.

There's no way at all to get a list of which packages are dependent on my/b since doing so would require scanning every project ever created by every person on the planet.