Merge pull request #84 from filaretov/virtual-environments

Conda and Python venv environment scripts

README.md

@@ -35,3 +35,5 @@ You can run nushell scripts in a few different ways.
 | prompt           | [git_status_prompt.nu](./prompt/git_status_prompt.nu)     | 0.28       | Creates a prompt which includes short working directory and current git status.        |
 | stdlib_candidate | [nu_style.nu](./stdlib_candidate/nu_style.nu)             | 0.26       | Define colors as names.        |
 | stdlib_candidate | [print.nu](./stdlib_candidate/print.nu)                   | 0.26       | Examples of a print statement.        |
+| virtual_envs     | [conda.nu](./virtual_environments/conda.nu)               | 0.32       | Activates a Conda environment. |
+| virtual_envs     | [venv.nu](./virtual_environments/venv.nu)                 | 0.32       | Activates a Python venv. |

virtual_environments/README.md

@@ -0,0 +1,53 @@
+# Virtual environment scripts
+
+The scripts in this directory activate virtual environments like Python venvs
+and Conda environments.  They follow the pattern described in the [Nushell 0.32
+changelog](https://www.nushell.sh/blog/2021-06-01-nushell_0_32.html#environment-loading-lily-mara):
+
+```
+$ load-env (activate some-env)
+```
+
+A custom command (`activate`) creates a table with environment variables and
+`load-env` is used to load it into the shell's scope.
+
+In most cases, deactivation is a matter of restoring the PATH variable to the
+state before activating the env and removing any additional variables. There are
+no environment-specific elements to this, which is why the same deactivation
+script can be used for deactivating any environment of a specific type.  For
+example, `source conda_deactivate.nu` will deactivate any Conda env, there are
+no input parameters.
+
+## Expected Usage
+
+1. Source an activation script in your `config.toml`. For example, `conda.nu`.
+   You'll then have the `conda-env` command available.
+2. Create an alias for sourcing the appropriate deactivation script:
+   `alias conda-deactivate = source /path/to/conda_deactivate.nu`
+3. Activate with `load-env (conda-env env-name)`. You might want to define some
+   shorter aliases for both commands, if typing that every time seems like a
+   hassle.
+4. If you're using [Starship](https://starship.rs/), your prompt should reflect the activated env.
+5. When done, deactivate with your alias: `conda-deactivate`.
+
+Look at the script files to find the exact command name for creating an environment table.
+
+## `conda.nu`
+
+Limitations:
+
+- The "root_prefix" might not actually correspond to the correct path to the Conda envs. You can fix
+  this for your setup by changing how the root prefix is found in the `conda-env` command.
+- Nested envs are not well supported. If you activate a Conda env while another one is
+  activated, new elements will be appended to the PATH, but the other environment
+  variables will be overwritten. There's no way to then restore the PATH to the state
+  it was in before activating the *first* env (at least not with this script directly).
+- The prompt is not updated by the script. Consider using [Starship](https://starship.rs/)
+  with the Python prompt element.
+
+## `venv.nu`
+
+Limitations:
+
+- The prompt is not updated by the script. Consider using [Starship](https://starship.rs/)
+  with the Python prompt element.

virtual_environments/conda.nu

@@ -0,0 +1,45 @@
+def conda-env [env-name] {
+    let conda-info = (conda info --envs --json | from json)
+    let suffix = (if $env-name == "base" {""} {(["envs" $env-name] | path join)})
+    let env-dir = ([$conda-info.root_prefix $suffix] | path join)
+    let old-path = ($nu.path | str collect (path-sep))
+    let new-path = (if (windows?) { (conda-create-path-windows $env-dir) } { (conda-create-path-unix $env-dir) })
+    let new-env = [[name, value];
+                   [CONDA_DEFAULT_ENV $env-name]
+                   [CONDA_PREFIX $env-dir]
+                   [CONDA_PROMPT_MODIFIER $"[($env-name)]"]
+                   [CONDA_SHLVL "1"]
+                   [CONDA_OLD_PATH $old-path]]
+     
+    $new-env | append $new-path
+}
+
+def conda-create-path-windows [env-dir] {
+    # 1. Conda on Windows needs a few additional Path elements
+    # 2. The path env var on Windows is called Path (not PATH)
+    let env-path = [
+        $env-dir
+        ([$env-dir "Scripts"] | path join)
+        ([$env-dir "Library" "mingw-w64"] | path join)
+        ([$env-dir "Library" "bin"] | path join)
+        ([$env-dir "Library" "usr" "bin"] | path join)
+    ]
+    let new-path = ([$env-path $nu.path] | flatten | str collect (path-sep))
+    [[name, value]; [Path $new-path]]
+}
+
+def conda-create-path-unix [env-dir] {
+    let env-path = [
+        ([$env-dir "bin"] | path join)
+    ]
+    let new-path = ([$env-path $nu.path] | flatten | str collect (path-sep))
+    [[name, value]; [PATH $new-path]]
+}
+
+def windows? [] {
+    (sys).host.name == "Windows"
+}
+
+def path-sep [] {
+    if (windows?) { ";" } { ":" }
+}

virtual_environments/conda_deactivate.nu

@@ -0,0 +1,7 @@
+let path-name = (if ((sys).host.name == "Windows") { "Path" } { "PATH" })
+let-env $path-name = $nu.env.CONDA_OLD_PATH
+unlet-env CONDA_PROMPT_MODIFIER
+unlet-env CONDA_PREFIX
+unlet-env CONDA_SHLVL
+unlet-env CONDA_DEFAULT_ENV
+unlet-env CONDA_OLD_PATH

virtual_environments/venv.nu

@@ -0,0 +1,33 @@
+def venv [venv-dir] {
+    let venv-abs-dir = ($venv-dir | path expand)
+    let venv-name = ($venv-abs-dir | path basename)
+    let old-path = ($nu.path | str collect (path-sep))
+    let new-path = (if (windows?) { (venv-path-windows $venv-abs-dir) } { (venv-path-unix $venv-abs-dir) })
+    let new-env = [[name, value];
+                   [VENV_OLD_PATH $old-path]
+                   [VIRTUAL_ENV $venv-name]]
+
+    $new-env | append $new-path
+}
+
+def venv-path-unix [venv-dir] {
+    let venv-path = ([$venv-dir "bin"] | path join)
+    let new-path = ($nu.path | prepend $venv-path | str collect (path-sep))
+    [[name, value]; [PATH $new-path]]
+}
+
+def venv-path-windows [venv-dir] {
+    # 1. Conda on Windows needs a few additional Path elements
+    # 2. The path env var on Windows is called Path (not PATH)
+    let venv-path = ([$venv-dir "Scripts"] | path join)
+    let new-path = ($nu.path | prepend $venv-path | str collect (path-sep))
+    [[name, value]; [Path $new-path]]
+}
+
+def windows? [] {
+    (sys).host.name == "Windows"
+}
+
+def path-sep [] {
+    if (windows?) { ";" } { ":" }
+}

virtual_environments/venv_deactivate.nu

@@ -0,0 +1,4 @@
+let path-name = (if ((sys).host.name == "Windows") { "Path" } { "PATH" })
+let-env $path-name = $nu.env.VENV_OLD_PATH
+unlet-env VIRTUAL_ENV
+unlet-env VENV_OLD_PATH