Add cache list command

This introduces a new cache sub-command that lists all available
caches.

Relates-to: python-poetry#1162

docs/docs/cli.md

@@ -452,3 +452,15 @@ The `env` command regroups sub commands to interact with the virtualenvs
 associated with a specific project.
 
 See [Managing environments](./managing-environments.md) for more information about these commands.
+
+## cache
+
+The `cache` command regroups sub commands to interact with Poetry's cache.
+
+### cache list
+
+The `cache list` command lists Poetry's available caches.
+
+```bash
+poetry cache list
+```

poetry/console/commands/cache/cache.py

@@ -1,3 +1,5 @@
+from poetry.console.commands.cache.list import CacheListCommand
+
 from ..command import Command
 from .clear import CacheClearCommand
 
@@ -7,7 +9,7 @@ class CacheCommand(Command):
     name = "cache"
     description = "Interact with Poetry's cache"
 
-    commands = [CacheClearCommand()]
+    commands = [CacheClearCommand(), CacheListCommand()]
 
     def handle(self):
         return self.call("help", self._config.name)

poetry/console/commands/cache/list.py

@@ -0,0 +1,21 @@
+import os
+
+from ..command import Command
+
+
+class CacheListCommand(Command):
+
+    name = "list"
+    description = "List Poetry's caches."
+
+    def handle(self):
+        from poetry.locations import REPOSITORY_CACHE_DIR
+
+        if os.path.exists(str(REPOSITORY_CACHE_DIR)):
+            caches = list(sorted(REPOSITORY_CACHE_DIR.iterdir()))
+            if caches:
+                for cache in caches:
+                    self.line("<info>{}</>".format(cache.name))
+                return 0
+
+        self.line("<warning>No caches found</>")

tests/console/commands/test_cache.py

@@ -0,0 +1,60 @@
+import uuid
+
+import pytest
+
+from cleo.testers import CommandTester
+
+
+@pytest.fixture
+def repository_cache_dir(monkeypatch, tmpdir):
+    import poetry.locations
+    from poetry.utils._compat import Path
+
+    path = Path(tmpdir)
+    monkeypatch.setattr(poetry.locations, "REPOSITORY_CACHE_DIR", path)
+    return path
+
+
+@pytest.fixture
+def repository_one():
+    return "01_{}".format(uuid.uuid4())
+
+
+@pytest.fixture
+def repository_two():
+    return "02_{}".format(uuid.uuid4())
+
+
+@pytest.fixture
+def mock_caches(repository_cache_dir, repository_one, repository_two):
+    (repository_cache_dir / repository_one).mkdir()
+    (repository_cache_dir / repository_two).mkdir()
+
+
+def test_cache_list(app, mock_caches, repository_one, repository_two):
+    command = app.find("cache list")
+    tester = CommandTester(command)
+
+    tester.execute()
+
+    expected = """\
+{}
+{}
+""".format(
+        repository_one, repository_two
+    )
+
+    assert expected == tester.io.fetch_output()
+
+
+def test_cache_list_empty(app, repository_cache_dir):
+    command = app.find("cache list")
+    tester = CommandTester(command)
+
+    tester.execute()
+
+    expected = """\
+No caches found
+"""
+
+    assert expected == tester.io.fetch_output()