Improve dependency resolution to avoid unnecessary operations

CHANGELOG.md

 # Change Log
 
+## [Unreleased]
+
+### Changed
+
+- Improved dependency resolution to avoid unnecessary operations.
+
+
 ## [0.6.5] - 2018-03-22
 
 ### Fixed

poetry/installation/installer.py

@@ -28,7 +28,8 @@ class Installer:
                  venv,
                  package: Package,
                  locker: Locker,
-                 pool: Pool):
+                 pool: Pool,
+                 installed: InstalledRepository = None):
         self._io = io
         self._venv = venv
         self._package = package
@@ -47,6 +48,7 @@ class Installer:
         self._extras = []
 
         self._installer = self._get_installer()
+        self._installed_repository = installed or self._get_installed()
 
     @property
     def installer(self):
@@ -116,11 +118,10 @@ class Installer:
 
     def _do_install(self, local_repo):
         locked_repository = Repository()
-        # initialize locked repo if we are installing from lock
-        if not self._update or (self._update and self._locker.is_locked()):
+        if self._update:
+            if self._locker.is_locked():
                 locked_repository = self._locker.locked_repository(True)
 
-        if self._update:
             # Checking extras
             for extra in self._extras:
                 if extra not in self._package.extras:
@@ -152,6 +153,7 @@ class Installer:
             solver = Solver(
                 self._package,
                 self._pool,
+                self._installed_repository,
                 locked_repository,
                 self._io
             )
@@ -162,6 +164,11 @@ class Installer:
             ops = solver.solve(request, fixed=fixed)
         else:
             self._io.writeln('<info>Installing dependencies from lock file</>')
+
+            locked_repository = self._locker.locked_repository(
+                self.is_dev_mode()
+            )
+
             if not self._locker.is_fresh():
                 self._io.writeln(
                     '<warning>'
@@ -342,7 +349,7 @@ class Installer:
     def _get_operations_from_lock(self,
                                   locked_repository: Repository
                                   ) -> List[Operation]:
-        installed_repo = InstalledRepository.load(self._venv)
+        installed_repo = self._installed_repository
         ops = []
 
         extra_packages = [
@@ -460,3 +467,6 @@ class Installer:
 
     def _get_installer(self) -> BaseInstaller:
         return PipInstaller(self._venv, self._io)
+
+    def _get_installed(self) -> InstalledRepository:
+        return InstalledRepository.load(self._venv)

poetry/puzzle/solver.py

@@ -18,9 +18,10 @@ from .ui import UI
 
 class Solver:
 
-    def __init__(self, package, pool, locked, io):
+    def __init__(self, package, pool, installed, locked, io):
         self._package = package
         self._pool = pool
+        self._installed = installed
         self._locked = locked
         self._io = io
 
@@ -79,7 +80,7 @@ class Solver:
         operations = []
         for package in packages:
             installed = False
-            for pkg in self._locked.packages:
+            for pkg in self._installed.packages:
                 if package.name == pkg.name:
                     installed = True
                     # Checking version
@@ -100,8 +101,12 @@ class Solver:
                     break
 
             if remove:
+                for locked in self._locked.packages:
+                    if locked.name == pkg.name:
                         operations.append(Uninstall(pkg))
 
+                        break
+
         return list(reversed(operations))
 
     def _get_tags_for_vertex(self, vertex, requested):

poetry/utils/venv.py

@@ -36,7 +36,6 @@ class Venv:
         if self._venv:
             self._venv = Path(self._venv)
 
-
         self._windows = sys.platform == 'win32'
 
         self._bin_dir = None

tests/installation/test_installer.py

@@ -115,8 +115,8 @@ def venv():
 
 
 @pytest.fixture()
-def installer(package, pool, locker, venv):
-    return Installer(NullIO(), venv, package, locker, pool)
+def installer(package, pool, locker, venv, installed):
+    return Installer(NullIO(), venv, package, locker, pool, installed=installed)
 
 
 def fixture(name):
@@ -461,7 +461,7 @@ def test_run_installs_extras_with_deps_if_requested(installer, locker, repo, pac
     assert len(installer.installs) == 4  # A, B, C, D
 
 
-def test_run_installs_extras_with_deps_if_requested_locked(installer, locker, repo, package, installed):
+def test_run_installs_extras_with_deps_if_requested_locked(installer, locker, repo, package):
     locker.locked(True)
     locker.mock_lock_data(fixture('extras-with-dependencies'))
     package.extras['foo'] = [

tests/puzzle/test_solver.py

@@ -30,6 +30,11 @@ def installed():
 
 
 @pytest.fixture()
+def locked():
+    return Repository()
+
+
+@pytest.fixture()
 def repo():
     return Repository()
 
@@ -40,8 +45,8 @@ def pool(repo):
 
 
 @pytest.fixture()
-def solver(package, pool, installed, io):
-    return Solver(package, pool, installed, io)
+def solver(package, pool, installed, locked, io):
+    return Solver(package, pool, installed, locked, io)
 
 
 def check_solver_result(ops, expected):
@@ -77,9 +82,9 @@ def test_solver_install_single(solver, repo):
     ])
 
 
-def test_solver_remove_if_not_installed(solver, installed):
+def test_solver_remove_if_no_longer_locked(solver, locked):
     package_a = get_package('A', '1.0')
-    installed.add_package(package_a)
+    locked.add_package(package_a)
 
     ops = solver.solve([])