[FEAT] pyrefly lsp config path customization

lsp/README.md

@@ -38,6 +38,9 @@ settings:
   but not find-references.
 - `pyrefly.lspPath` [string: '']: if your platform is not supported, you can
   build pyrefly from source and specify the binary here.
+- `pyrefly.configPath` [string: '']: path to a `pyrefly.toml` or
+  `pyproject.toml` configuration file. When set, the LSP will use this config
+  for all files instead of an upward-filesystem-walk discovery approach.
 - `python.analysis.showHoverGoToLinks` [boolean: true]: Controls whether hover
   tooltips include "Go to definition" and "Go to type definition" navigation
   links. Set to `false` for cleaner tooltips with only type information.

lsp/package.json

@@ -240,6 +240,12 @@
                     "type": "boolean",
                     "default": false,
                     "description": "Controls whether comment section folding ranges are included in the editor. When true, comments following the pattern '# Section Name ----' (with 4+ trailing dashes) create collapsible regions, similar to R's code section convention."
+                },
+                "pyrefly.configPath": {
+                    "type": "string",
+                    "default": "",
+                    "description": "Path to a pyrefly.toml or pyproject.toml configuration file. When set, the LSP will use this config for all files instead of an upward-filesystem-walk config discovery approach.",
+                    "scope": "resource"
                 }
             }
         }

pyrefly/lib/commands/files.rs

@@ -45,7 +45,7 @@ pub struct FilesArgs {
     #[arg(long)]
     project_excludes: Option<Vec<String>>,
 
-    /// Explicitly set the Pyrefly configuration to use when type checking or starting a language server.
+    /// Explicitly set the Pyrefly configuration to use when type checking.
     /// In "single-file checking mode," this config is applied to all files being checked, ignoring
     /// the config's `project_includes` and `project_excludes` and ignoring any config-finding approach
     /// that would otherwise be used.

pyrefly/lib/commands/lsp.rs

@@ -6,12 +6,14 @@
  */
 
 use std::io::Write;
+use std::path::PathBuf;
 use std::sync::Arc;
 
 use clap::Parser;
 use clap::ValueEnum;
 use lsp_types::InitializeParams;
 use lsp_types::ServerInfo;
+use pyrefly_util::args::clap_env;
 use pyrefly_util::telemetry::Telemetry;
 
 use crate::commands::util::CommandExitStatus;
@@ -57,6 +59,12 @@ pub struct LspArgs {
     /// an up-to-date source DB. Only useful for benchmarking.
     #[arg(long)]
     pub(crate) build_system_blocking: bool,
+
+    /// Explicitly set the Pyrefly configuration file to use.
+    /// When set, the LSP will use this config for all files instead of the
+    /// upward-filesystem-walk discovery approach.
+    #[arg(long, short, value_name = "FILE", env = clap_env("CONFIG"))]
+    pub(crate) config: Option<PathBuf>,
 }
 
 /// Run LSP server with optional path remapping.
@@ -80,6 +88,7 @@ pub fn run_lsp(
             args.indexing_mode,
             args.workspace_indexing_limit,
             args.build_system_blocking,
+            args.config,
             path_remapper,
             telemetry,
             external_references,

pyrefly/lib/commands/tsp.rs

@@ -51,6 +51,7 @@ pub fn run_tsp(
             args.indexing_mode,
             args.workspace_indexing_limit,
             false,
+            None, // No explicit config for TSP
             surface,
             None, // No path remapping for TSP
             Arc::new(NoExternalReferences),

pyrefly/lib/lsp/non_wasm/server.rs

@@ -233,6 +233,7 @@ use crate::binding::binding::KeyClass;
 use crate::binding::binding::KeyClassMro;
 use crate::commands::lsp::IndexingMode;
 use crate::config::config::ConfigFile;
+use crate::config::finder::ConfigFinder;
 use crate::error::error::Error;
 use crate::lsp::module_helpers::to_real_path;
 use crate::lsp::non_wasm::build_system::should_requery_build_system;
@@ -1015,6 +1016,7 @@ pub fn lsp_loop(
     indexing_mode: IndexingMode,
     workspace_indexing_limit: usize,
     build_system_blocking: bool,
+    config: Option<PathBuf>,
     path_remapper: Option<PathRemapper>,
     telemetry: &impl Telemetry,
     external_references: Arc<dyn ExternalReferences>,
@@ -1029,6 +1031,7 @@ pub fn lsp_loop(
         indexing_mode,
         workspace_indexing_limit,
         build_system_blocking,
+        config,
         from,
         path_remapper,
         external_references,
@@ -1913,6 +1916,7 @@ impl Server {
         indexing_mode: IndexingMode,
         workspace_indexing_limit: usize,
         build_system_blocking: bool,
+        config: Option<PathBuf>,
         surface: Option<String>,
         path_remapper: Option<PathRemapper>,
         external_references: Arc<dyn ExternalReferences>,
@@ -1931,7 +1935,27 @@ impl Server {
 
         let workspaces = Arc::new(Workspaces::new(Workspace::default(), &folders));
 
-        let config_finder = Workspaces::config_finder(workspaces.dupe());
+        // Resolve the config path: CLI --config takes precedence, then
+        // initializationOptions.configPath from the editor.
+        let explicit_config = config.or_else(|| {
+            initialize_params
+                .initialization_options
+                .as_ref()
+                .and_then(|opts| opts.get("configPath"))
+                .and_then(|v| v.as_str())
+                .filter(|s| !s.is_empty())
+                .map(PathBuf::from)
+        });
+
+        let config_finder = if let Some(config_path) = explicit_config {
+            let (mut config_file, mut errors) = ConfigFile::from_file(&config_path);
+            errors.extend(config_file.configure());
+            let finder = ConfigFinder::new_constant(ArcId::new(config_file));
+            finder.add_errors(errors);
+            finder
+        } else {
+            Workspaces::config_finder(workspaces.dupe())
+        };
 
         // Parse commentFoldingRanges from initialization options, defaults to false
         let comment_folding_ranges = initialize_params

pyrefly/lib/test/lsp/lsp_interaction/object_model.rs

@@ -1254,6 +1254,7 @@ impl LspInteraction {
                 indexing_mode,
                 workspace_indexing_limit: 50,
                 build_system_blocking: false,
+                config: None,
             };
             let _ = run_lsp(
                 conn_server,

website/docs/IDE.mdx

@@ -42,6 +42,8 @@ The following configuration options are IDE-specific and exposed as VSCode setti
   - `python.pyrefly.displayTypeErrors` [enum: default, force-on, force-off, error-missing-imports]: If `'default'`, Pyrefly will only provide type checking diagnostics in the IDE if your file is covered by a [Pyrefly configuration](../configuration). If `'force-off'`, Pyrefly will never provide type check diagnostics in the IDE. If `'force-on'`, Pyrefly will always provide type check diagnostics in the IDE. If `'error-missing-imports'`, Pyrefly will only show errors for missing imports and missing sources (`missing-import`, `missing-source`, and `missing-source-for-stubs`). Note that syntax errors (`invalid-syntax` and `parse-error`) are shown by default in every mode besides `force-off`.
 - Specify a custom Pyrefly Binary (lspPath)
   - `pyrefly.lspPath` [string: '']: If your platform is not supported, you can build pyrefly from source and specify the binary path with the `lspPath` config.
+- Specify a custom configuration file (configPath)
+  - `pyrefly.configPath` [string: '']: Path to a `pyrefly.toml` or `pyproject.toml` configuration file. When set, the LSP will use this config for all files instead of an upward-filesystem-walk discovery approach.
 - Use a specific interpreter
   - If the [`Python`](https://marketplace.visualstudio.com/items?itemName=ms-python.python) VSCode extension is installed, [selecting an interpreter](https://code.visualstudio.com/docs/python/environments) will override the interpreter and settings Pyrefly uses to type check your project, even if one is specified in your Pyrefly configuration.
   - `python.defaultInterpreterPath` will override the default interpreter selected by VSCode for your workspace.