Add the cache:clear command

CHANGELOG.md

 # Change Log
 
+[Unreleased]
+
+### Added
+
+- Added the `cache:clear` command.
+
+
 ## [0.8.3] - 2018-04-16
 
 ### Fixed

poetry/console/application.py

@@ -25,6 +25,8 @@ from .commands import ShowCommand
 from .commands import UpdateCommand
 from .commands import VersionCommand
 
+from .commands.cache import CacheClearCommand
+
 from .commands.debug import DebugInfoCommand
 from .commands.debug import DebugResolveCommand
 
@@ -109,6 +111,11 @@ class Application(BaseApplication):
             VersionCommand(),
         ]
 
+        # Cache commands
+        commands += [
+            CacheClearCommand(),
+        ]
+
         # Debug commands
         commands += [
             DebugInfoCommand(),

poetry/console/commands/cache/__init__.py

+from .clear import CacheClearCommand

poetry/console/commands/cache/clear.py

+import os
+import shutil
+
+from ..command import Command
+
+
+class CacheClearCommand(Command):
+    """
+    Clears poetry's cache.
+
+    cache:clear
+        { cache : The name of the cache to clear. }
+        { --all : Clear all caches. }
+    """
+
+    def handle(self):
+        from cachy import CacheManager
+        from poetry.locations import CACHE_DIR
+
+        cache = self.argument('cache')
+
+        parts = cache.split(':')
+        cache_dir = os.path.join(CACHE_DIR, 'cache', 'repositories', parts[0])
+        cache = CacheManager({
+            'default': parts[0],
+            'serializer': 'json',
+            'stores': {
+                parts[0]: {
+                    'driver': 'file',
+                    'path': cache_dir
+                }
+            }
+        })
+
+        if len(parts) == 1:
+            if not self.option('all'):
+                raise RuntimeError(
+                    'Add the --all option if you want to clear all '
+                    '{} caches'.format(parts[0])
+                )
+
+            if not os.path.exists(cache_dir):
+                self.line('No cache entries for {}'.format(parts[0]))
+                return 0
+
+            # Calculate number of entries
+            entries_count = 0
+            for path, dirs, files in os.walk(cache_dir):
+                entries_count += len(files)
+
+            delete = self.confirm(
+                '<question>Delete {} entries?</>'.format(entries_count)
+            )
+            if not delete:
+                return 0
+
+            cache.flush()
+        elif len(parts) == 2:
+            raise RuntimeError(
+                'Only specifying the package name is not yet supported. '
+                'Add a specific version to clear'
+            )
+        elif len(parts) == 3:
+            package = parts[1]
+            version = parts[2]
+
+            if not cache.has('{}:{}'.format(package, version)):
+                self.line(
+                    'No cache entries for {}:{}'.format(package, version)
+                )
+                return 0
+
+            delete = self.confirm(
+                'Delete cache entry {}:{}'.format(package, version)
+            )
+            if not delete:
+                return 0
+
+            cache.forget('{}:{}'.format(package, version))
+        else:
+            raise ValueError('Invalid cache key')