scip: Allow customizing cargo config.

Re-use the LSP config json for simplicity.

crates/rust-analyzer/src/cli/flags.rs

@@ -131,6 +131,9 @@ xflags::xflags! {
 
             /// The output path where the SCIP file will be written to. Defaults to `index.scip`.
             optional --output path: PathBuf
+
+            /// A path to an json configuration file that can be used to customize cargo behavior.
+            optional --config-path config_path: PathBuf
         }
     }
 }
@@ -239,6 +242,7 @@ pub struct Scip {
     pub path: PathBuf,
 
     pub output: Option<PathBuf>,
+    pub config_path: Option<PathBuf>,
 }
 
 impl RustAnalyzer {

crates/rust-analyzer/src/cli/scip.rs

@@ -12,7 +12,6 @@ use ide::{
 };
 use ide_db::LineIndexDatabase;
 use load_cargo::{load_workspace_at, LoadCargoConfig, ProcMacroServerChoice};
-use project_model::{CargoConfig, RustLibSource};
 use scip::types as scip_types;
 
 use crate::{
@@ -24,8 +23,6 @@ impl flags::Scip {
     pub fn run(self) -> anyhow::Result<()> {
         eprintln!("Generating SCIP start...");
         let now = Instant::now();
-        let mut cargo_config = CargoConfig::default();
-        cargo_config.sysroot = Some(RustLibSource::Discover);
 
         let no_progress = &|s| (eprintln!("rust-analyzer: Loading {s}"));
         let load_cargo_config = LoadCargoConfig {
@@ -34,6 +31,20 @@ impl flags::Scip {
             prefill_caches: true,
         };
         let root = vfs::AbsPathBuf::assert(std::env::current_dir()?.join(&self.path)).normalize();
+
+        let mut config = crate::config::Config::new(
+            root.clone(),
+            lsp_types::ClientCapabilities::default(),
+            /* workspace_roots = */ vec![],
+            /* is_visual_studio_code = */ false,
+        );
+
+        if let Some(p) = self.config_path {
+            let mut file = std::io::BufReader::new(std::fs::File::open(p)?);
+            let json = serde_json::from_reader(&mut file)?;
+            config.update(json)?;
+        }
+        let cargo_config = config.cargo();
         let (host, vfs, _) = load_workspace_at(
             root.as_path().as_ref(),
             &cargo_config,

crates/rust-analyzer/src/config.rs

@@ -766,6 +766,8 @@ impl fmt::Display for ConfigError {
     }
 }
 
+impl std::error::Error for ConfigError {}
+
 impl Config {
     pub fn new(
         root_path: AbsPathBuf,