lock: allow for no-update refresh of lock files

Relates-to: #3028

poetry/console/commands/lock.py

@@ -1,3 +1,5 @@
+from cleo import option
+
 from .installer_command import InstallerCommand
 
 
@@ -6,6 +8,12 @@ class LockCommand(InstallerCommand):
     name = "lock"
     description = "Locks the project dependencies."
 
+    options = [
+        option(
+            "no-update", None, "Do not update locked versions, only refresh lock file."
+        ),
+    ]
+
     help = """
 The <info>lock</info> command reads the <comment>pyproject.toml</> file from the
 current directory, processes it, and locks the dependencies in the <comment>poetry.lock</>
@@ -21,6 +29,6 @@ def handle(self):
             self.poetry.config.get("experimental.new-installer", False)
         )
 
-        self._installer.lock()
+        self._installer.lock(self.option("no-update"))
 
         return self._installer.run()

poetry/installation/installer.py

@@ -85,6 +85,10 @@ def set_locker(self, locker):  # type: (Locker) -> Installer
         return self
 
     def run(self):
+        # Check if refresh
+        if not self._update and self._lock and self._locker.is_locked():
+            self._do_refresh()
+
         # Force update if there is no lock file present
         if not self._update and not self._locker.is_locked():
             self._update = True
@@ -137,11 +141,11 @@ def update(self, update=True):  # type: (bool) -> Installer
 
         return self
 
-    def lock(self):  # type: () -> Installer
+    def lock(self, update=True):  # type: (bool) -> Installer
         """
         Prepare the installer for locking only.
         """
-        self.update()
+        self.update(update=update)
         self.execute_operations(False)
         self._lock = True
 
@@ -173,6 +177,33 @@ def use_executor(self, use_executor=True):  # type: (bool) -> Installer
 
         return self
 
+    def _do_refresh(self):
+        from poetry.puzzle import Solver
+
+        locked_repository = self._locker.locked_repository(True)
+
+        # Checking extras
+        for extra in self._extras:
+            if extra not in self._package.extras:
+                raise ValueError("Extra [{}] is not specified.".format(extra))
+
+        solver = Solver(
+            self._package,
+            self._pool,
+            self._installed_repository,
+            locked_repository,
+            self._io,
+            remove_untracked=self._remove_untracked,
+        )
+
+        ops = solver.solve(use_latest=[])
+
+        local_repo = Repository()
+        self._populate_local_repo(local_repo, ops)
+
+        if self._update or self._lock:
+            self._write_lock_file(local_repo)
+
     def _do_install(self, local_repo):
         from poetry.puzzle import Solver
 
@@ -229,7 +260,7 @@ def _do_install(self, local_repo):
 
         self._populate_local_repo(local_repo, ops)
 
-        if self._update:
+        if self._update or self._lock:
             self._write_lock_file(local_repo)
 
             if self._lock: