Fix detection of R languageserver

CHANGELOG.md

@@ -5,8 +5,10 @@
 - bug fixes:
 
   - send periodic pings on websocket channels to maintain connection ([#459], thanks @franckchen)
+  - R languageserver is no longer incorrectly shown as available when not installed ([#463])
 
 [#459]: https://github.com/krassowski/jupyterlab-lsp/pull/459
+[#463]: https://github.com/krassowski/jupyterlab-lsp/pull/463
 
 ### `@krassowski/jupyterlab-lsp 3.0.0` (2021-01-06)
 

docs/Configuring.ipynb

@@ -59,8 +59,13 @@
    "source": [
     "The absolute minimum language server spec requires:\n",
     "\n",
-    "- `argv`, a list of shell tokens to launch the server in `stdio` mode (as\n",
+    "- `argv`, a list of _shell tokens_ to launch the server in `stdio` mode (as\n",
     "  opposed to `tcp`),\n",
+    "  - _shell tokens_ are arrays of strings representing command line commands with\n",
+    "    arguments, for example `ls -l` is represented as `[\"ls\", \"-l\"]` while\n",
+    "    `mkdir \"new directory\"` should be split into `[\"mkdir\", \"new directory\"]`;\n",
+    "    If you have Python installed, you can use `shlex.split(\"your command\")` to\n",
+    "    get such an array.\n",
     "- the `languages` which the server will respond to, and\n",
     "- the schema `version` of the spec (currently `2`)\n",
     "\n",

docs/Extending.ipynb

@@ -16,10 +16,10 @@
     "### How to add a new LSP feature?\n",
     "\n",
     "Features (as well as other parts of the frontend) reuse the\n",
-    "[JupyterLab plugins system](https://jupyterlab.readthedocs.io/en/stable/developer/extension_dev.html#plugins).\n",
+    "[JupyterLab plugins system](https://jupyterlab.readthedocs.io/en/stable/extension/extension_dev.html#plugins).\n",
     "Each plugin is a [TypeScript](https://www.typescriptlang.org/) package exporting\n",
     "one or more `JupyterFrontEndPlugin`s (see\n",
-    "[the JupyterLab extesion developer tutorial](https://jupyterlab.readthedocs.io/en/stable/developer/extension_tutorial.html)\n",
+    "[the JupyterLab extesion developer tutorial](https://jupyterlab.readthedocs.io/en/stable/extension/extension_tutorial.html)\n",
     "for an overview). Each feature has to register itself with the `FeatureManager`\n",
     "(which is provided after requesting `ILSPFeatureManager` token) using\n",
     "`register(options: IFeatureOptions)` method.\n",
@@ -41,7 +41,7 @@
     "\n",
     "For further integration with the JupyterLab, you can request additional\n",
     "JupyterLab tokens (consult JupyterLab documentation on\n",
-    "[core tokens](https://jupyterlab.readthedocs.io/en/stable/developer/extension_dev.html#core-tokens)).\n",
+    "[core tokens](https://jupyterlab.readthedocs.io/en/stable/extension/extension_points.html#core-tokens)).\n",
     "\n",
     "#### How to override the default implementation of a feature?\n",
     "\n",

python_packages/jupyter_lsp/jupyter_lsp/specs/r_languageserver.py

@@ -1,10 +1,19 @@
-from .utils import HELPERS, ShellSpec
+from .utils import ShellSpec
 
 
 class RLanguageServer(ShellSpec):
+    package = "languageserver"
     key = "r-languageserver"
     cmd = "Rscript"
-    args = ["--slave", str(HELPERS / "languageserver.R")]
+
+    @property
+    def args(self):
+        return ["--slave", "-e", f"{self.package}::run()"]
+
+    @property
+    def is_installed_args(self):
+        return ["-e", f"cat(system.file(package='{self.package}'))"]
+
     languages = ["r"]
     spec = dict(
         display_name=key,
@@ -14,7 +23,7 @@ class RLanguageServer(ShellSpec):
             issues="https://github.com/REditorSupport/languageserver/issues",
         ),
         install=dict(
-            cran='install.packages("languageserver")',
+            cran=f'install.packages("{package}")',
             conda="conda install -c conda-forge r-languageserver",
         ),
     )

python_packages/jupyter_lsp/jupyter_lsp/specs/utils.py

@@ -2,7 +2,8 @@
 import shutil
 import sys
 from pathlib import Path
-from typing import List, Text
+from subprocess import check_output
+from typing import List, Text, Union
 
 from ..schema import SPEC_VERSION
 from ..types import (
@@ -17,13 +18,17 @@
 # when building docs, let all specs go through
 BUILDING_DOCS = os.environ.get("JUPYTER_LSP_BUILDING_DOCS") is not None
 
+# String corresponding to a fragment of a shell command
+# arguments list such as returned by `shlex.split`
+Token = Text
+
 
 class SpecBase:
     """Base for a spec finder that returns a spec for starting a language server"""
 
     key = ""
     languages = []  # type: List[Text]
-    args = []  # type: List[Text]
+    args = []  # type: List[Token]
     spec = {}  # type: LanguageServerSpec
 
     def __call__(
@@ -39,6 +44,23 @@ class ShellSpec(SpecBase):  # pragma: no cover
 
     cmd = ""
 
+    # [optional] arguments passed to `cmd` which upon execution should print
+    # out a non-empty string if the the required language server package
+    # is installed, or nothing if it is missing and user action is required.
+    is_installed_args = []  # type: List[Token]
+
+    def is_installed(self, cmd: Union[str, None]) -> bool:
+        if not cmd:
+            return False
+
+        if not self.is_installed_args:
+            return bool(cmd)
+        else:
+            check_result = check_output([cmd, *self.is_installed_args]).decode(
+                encoding="utf-8"
+            )
+            return check_result != ""
+
     def __call__(self, mgr: LanguageServerManagerAPI) -> KeyedLanguageServerSpecs:
         for ext in ["", ".cmd", ".bat", ".exe"]:
             cmd = shutil.which(self.cmd + ext)
@@ -48,7 +70,7 @@ def __call__(self, mgr: LanguageServerManagerAPI) -> KeyedLanguageServerSpecs:
         if not cmd and BUILDING_DOCS:  # pragma: no cover
             cmd = self.cmd
 
-        if not cmd:  # pragma: no cover
+        if not self.is_installed(cmd):  # pragma: no cover
             return {}
 
         return {

python_packages/jupyter_lsp/jupyter_lsp/tests/test_detect.py

@@ -1,3 +1,8 @@
+import shutil
+
+from jupyter_lsp.specs.r_languageserver import RLanguageServer
+
+
 def test_no_detect(manager):
     """should not enable anything by default"""
     manager.autodetect = False
@@ -9,3 +14,17 @@ def test_no_detect(manager):
 def test_detect(manager):
     manager.initialize()
     assert len(manager.sessions) == len(manager.language_servers)
+
+
+def test_r_package_detection():
+    existing_runner = shutil.which("Rscript")
+
+    with_installed_server = RLanguageServer()
+    assert with_installed_server.is_installed(cmd=existing_runner) is True
+    assert with_installed_server.is_installed(cmd=None) is False
+
+    class NonInstalledRServer(RLanguageServer):
+        package = "languageserver-fork"
+
+    non_installed_server = NonInstalledRServer()
+    assert non_installed_server.is_installed(cmd=existing_runner) is False