From 1b7b680bb5ff655087792df7fd81757b8d0795f2 Mon Sep 17 00:00:00 2001
From: Xavi Simpson <xavisimpson@meta.com>
Date: Tue, 8 Jul 2025 17:36:47 -0400
Subject: [PATCH] Add Pyrefly LSP specification

---
 CHANGELOG.md                                  |  5 ++++
 .../jupyter_lsp/jupyter_lsp/specs/__init__.py |  2 ++
 .../jupyter_lsp/specs/config/README.md        |  1 +
 .../specs/config/pyrefly.schema.json          | 19 +++++++++++++++
 .../jupyter_lsp/jupyter_lsp/specs/pyrefly.py  | 23 +++++++++++++++++++
 python_packages/jupyter_lsp/setup.cfg         |  1 +
 6 files changed, 51 insertions(+)
 create mode 100644 python_packages/jupyter_lsp/jupyter_lsp/specs/config/pyrefly.schema.json
 create mode 100644 python_packages/jupyter_lsp/jupyter_lsp/specs/pyrefly.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0fbe67cbc..5272c00c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 ## Changelog
 
+### `jupyter-lsp (next)`
+
+- features:
+  - add auto-detection of Pyrefly language server ([#1136](https://github.com/jupyter-lsp/jupyterlab-lsp/issues/1136))
+
 ### `@jupyter-lsp/jupyterlab-lsp 5.2.0`
 
 - enhancements:
diff --git a/python_packages/jupyter_lsp/jupyter_lsp/specs/__init__.py b/python_packages/jupyter_lsp/jupyter_lsp/specs/__init__.py
index f5b90072c..ce741e770 100644
--- a/python_packages/jupyter_lsp/jupyter_lsp/specs/__init__.py
+++ b/python_packages/jupyter_lsp/jupyter_lsp/specs/__init__.py
@@ -10,6 +10,7 @@
 from .julia_language_server import JuliaLanguageServer
 from .pyls import PalantirPythonLanguageServer
 from .pyright import PyrightLanguageServer
+from .pyrefly import PyreflyLanguageServer
 from .python_lsp_server import PythonLSPServer
 from .r_languageserver import RLanguageServer
 from .sql_language_server import SQLLanguageServer
@@ -31,6 +32,7 @@
 md = UnifiedLanguageServer()
 py_palantir = PalantirPythonLanguageServer()
 py_lsp_server = PythonLSPServer()
+pyrefly = PyreflyLanguageServer()
 pyright = PyrightLanguageServer()
 r = RLanguageServer()
 tex = Texlab()
diff --git a/python_packages/jupyter_lsp/jupyter_lsp/specs/config/README.md b/python_packages/jupyter_lsp/jupyter_lsp/specs/config/README.md
index d8e1937cf..44d508df9 100644
--- a/python_packages/jupyter_lsp/jupyter_lsp/specs/config/README.md
+++ b/python_packages/jupyter_lsp/jupyter_lsp/specs/config/README.md
@@ -7,6 +7,7 @@ These are configuration schemas extracted from canonical upstreams:
 - [dockerfile-language-server-nodejs](https://github.com/microsoft/vscode-docker/blob/master/package.json)
 - [yaml-language-server](https://github.com/redhat-developer/vscode-yaml/blob/master/package.json)
 - [pyright](https://github.com/microsoft/pyright/blob/main/packages/vscode-pyright/package.json)
+- [pyrefly](https://github.com/facebook/pyrefly/blob/main/lsp/package.json)
 
 > All of the configurations are sent to the Language Server, but only some of them
 > are actually acted upon, but we don't know which is which, yet.
diff --git a/python_packages/jupyter_lsp/jupyter_lsp/specs/config/pyrefly.schema.json b/python_packages/jupyter_lsp/jupyter_lsp/specs/config/pyrefly.schema.json
new file mode 100644
index 000000000..5b3ddd36f
--- /dev/null
+++ b/python_packages/jupyter_lsp/jupyter_lsp/specs/config/pyrefly.schema.json
@@ -0,0 +1,19 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Pyrefly Language Server Configuration",
+  "type": "object",
+  "properties": {
+    "python.pyrefly.disableTypeErrors": {
+      "type": "boolean",
+      "default": false,
+      "description": "If true, pyrefly will not provide typecheck squiggles in the IDE. To control other IDE services, see `python.pyrefly.disableLanguageServices`",
+      "scope": "resource"
+    },
+    "python.pyrefly.disableLanguageServices": {
+      "type": "boolean",
+      "default": false,
+      "description": "If true, pyrefly will not provide other IDE services like completions, hover, definition, etc. To control type errors, see `python.pyrefly.disableTypeErrors`",
+      "scope": "resource"
+    }
+  }
+}
diff --git a/python_packages/jupyter_lsp/jupyter_lsp/specs/pyrefly.py b/python_packages/jupyter_lsp/jupyter_lsp/specs/pyrefly.py
new file mode 100644
index 000000000..884d8efd4
--- /dev/null
+++ b/python_packages/jupyter_lsp/jupyter_lsp/specs/pyrefly.py
@@ -0,0 +1,23 @@
+from .config import load_config_schema
+from .utils import ShellSpec
+
+
+class PyreflyLanguageServer(ShellSpec):
+    key = cmd = "pyrefly"
+    args = ["lsp"]
+    languages = ["python"]
+    spec = dict(
+        display_name="Pyrefly",
+        mime_types=["text/python", "text/x-ipython"],
+        urls=dict(
+            home="https://github.com/facebook/pyrefly",
+            issues="https://github.com/facebook/pyrefly/issues",
+        ),
+        install=dict(
+            pip="pip install pyrefly",
+            uv="uv add pyrefly",
+            conda="conda install -c conda-forge pyrefly",
+        ),
+        config_schema=load_config_schema(key),
+        requires_documents_on_disk=False
+    )
diff --git a/python_packages/jupyter_lsp/setup.cfg b/python_packages/jupyter_lsp/setup.cfg
index 51f7f5e4d..8d092f459 100644
--- a/python_packages/jupyter_lsp/setup.cfg
+++ b/python_packages/jupyter_lsp/setup.cfg
@@ -44,6 +44,7 @@ jupyter_lsp_spec_v1 =
     julia-language-server = jupyter_lsp.specs:julia
     python-language-server = jupyter_lsp.specs:py_palantir
     python-lsp-server = jupyter_lsp.specs:py_lsp_server
+    pyrefly = jupyter_lsp.specs:pyrefly
     pyright = jupyter_lsp.specs:pyright
     r-languageserver = jupyter_lsp.specs:r
     texlab = jupyter_lsp.specs:tex