feat: Add a global cache for uv, pre-commit and global venv

.devcontainer/devcontainer.json

@@ -8,16 +8,22 @@
     "remoteEnv": {
         // Allow X11 apps to run inside the container
         "DISPLAY": "${localEnv:DISPLAY}",
+        // Put things that allow it in the persistent cache
+        "PRE_COMMIT_HOME": "/cache/pre-commit",
+        "UV_CACHE_DIR": "/cache/uv",
+        "UV_PYTHON_CACHE_DIR": "/cache/uv-python",
+        // Make a venv that is specific for this workspace path as the cache is shared
+        "UV_PROJECT_ENVIRONMENT": "/cache/venv-for${localWorkspaceFolder}",
         // Do the equivalent of "activate" the venv so we don't have to "uv run" everything
-        "VIRTUAL_ENV": "/workspaces/${localWorkspaceFolderBasename}/.venv",
-        "PATH": "/workspaces/${localWorkspaceFolderBasename}/.venv/bin:${containerEnv:PATH}"
+        "VIRTUAL_ENV": "/cache/venv-for${localWorkspaceFolder}",
+        "PATH": "/cache/venv-for${localWorkspaceFolder}/bin:${containerEnv:PATH}"
     },
     "customizations": {
         "vscode": {
             // Set *default* container specific settings.json values on container create.
             "settings": {
                 // Use the container's python by default
-                "python.defaultInterpreterPath": "/workspaces/${localWorkspaceFolderBasename}/.venv/bin/python",
+                "python.defaultInterpreterPath": "/cache/venv-for${localWorkspaceFolder}/bin/python",
                 // Don't activate the venv as it is already in the PATH
                 "python.terminal.activateEnvInCurrentTerminal": false,
                 "python.terminal.activateEnvironment": false,
@@ -38,9 +44,7 @@
         }
     },
     // Create the config folder for the bash-config feature and uv cache
-    // NOTE: The uv cache can get large, DLS users should read
-    // https://dev-guide.diamond.ac.uk/linux-user-environment/how-tos/disk-quota-troubleshooting
-    "initializeCommand": "mkdir -p ${localEnv:HOME}/.config/terminal-config ${localEnv:HOME}/.cache/uv",
+    "initializeCommand": "mkdir -p ${localEnv:HOME}/.config/terminal-config",
     "runArgs": [
         // Allow the container to access the host X11 display and EPICS CA
         "--net=host",
@@ -54,20 +58,15 @@
             "target": "/user-terminal-config",
             "type": "bind"
         },
-        // Keep a persistent cross container cache for uv
+        // Keep a persistent cross container cache for uv, pre-commit, and the venvs
         {
-            "source": "${localEnv:HOME}/.cache/uv",
-            "target": "/root/.cache/uv",
-            "type": "bind"
-        },
-        // Use a volume mount for the uv venv so it is local to the container
-        {
-            "target": "/workspaces/${localWorkspaceFolderBasename}/.venv",
+            "source": "devcontainer-shared-cache",
+            "target": "/cache",
             "type": "volume"
         }
     ],
     // Mount the parent as /workspaces so we can pip install peers as editable
     "workspaceMount": "source=${localWorkspaceFolder}/..,target=/workspaces,type=bind",
-    // After the container is created, install the python project in editable form
-    "postCreateCommand": "uv sync && uv run pre-commit install --install-hooks"
+    // After the container is created, recreate the venv then make pre-commit first run faster
+    "postCreateCommand": "uv venv --clear && uv sync && pre-commit install --install-hooks"
 }

docs/how-to/dev-install.md

@@ -20,11 +20,11 @@ code .
 
 Click on 'Reopen in Container' when prompted on startup or, if vscode is already running, open the command menu with CTRL+SHIFT+P, search for and run 'Reopen in Container'.
 
-Open a new terminal
+The developer container creates and activates a venv (stored in `/cache/venv-for/path/to/project`) and this will be managed by any `uv sync` command as explained in [](./lock-requirements.md). Any rebuild of the container will recreate this venv, but the dependencies will be stored in a cross container cache so that rebuilds are quick.
 
 ## Build and test
 
-Now you have a development environment you can run the tests in a terminal:
+Now you have a development environment you can run the tests in a new terminal:
 
 ```
 tox -p

docs/how-to/lock-requirements.md

@@ -32,3 +32,11 @@ uv sync --upgrade
 ```{seealso}
 [The uv docs on locking and syncing](https://docs.astral.sh/uv/concepts/projects/sync)
 ```
+
+## Modifying the venv to add other projects
+
+Peer projects (those checked out next to the project) are visible in the devcontainer, and can be added into the venv by running `uv pip install -e ../other_project`. This will allow live changes made in this other project to be immediately reflected in the venv.
+
+```{note}
+This venv is activated by default, and global to the container, so if you `uv sync` from `other_project` then it will **replace** the contents of the venv with `other_project`'s dependencies.
+```