Merge get_sysroot_src into the constructor

src/main.rs

@@ -204,10 +204,7 @@ fn main() -> Result<()> {
         }
 
         Subcommands::Lsp => {
-            let mut project = RustAnalyzerProject::new();
+            let mut project = RustAnalyzerProject::build()?;
-            project
-                .get_sysroot_src()
-                .expect("Couldn't find toolchain path, do you have `rustc` installed?");
             project
                 .exercises_to_json()
                 .expect("Couldn't parse rustlings exercises files");

src/project.rs

@@ -1,3 +1,4 @@
+use anyhow::{bail, Context, Result};
 use glob::glob;
 use serde::{Deserialize, Serialize};
 use std::env;
@@ -22,11 +23,44 @@ pub struct Crate {
 }
 
 impl RustAnalyzerProject {
-    pub fn new() -> RustAnalyzerProject {
+    pub fn build() -> Result<Self> {
-        RustAnalyzerProject {
+        // check if RUST_SRC_PATH is set
-            sysroot_src: String::new(),
+        if let Ok(sysroot_src) = env::var("RUST_SRC_PATH") {
+            return Ok(Self {
+                sysroot_src,
                 crates: Vec::new(),
+            });
         }
+
+        let toolchain = Command::new("rustc")
+            .arg("--print")
+            .arg("sysroot")
+            .output()
+            .context("Failed to get the sysroot from `rustc`. Do you have `rustc` installed?")?
+            .stdout;
+
+        let toolchain =
+            String::from_utf8(toolchain).context("The toolchain path is invalid UTF8")?;
+        let toolchain = toolchain.trim_end();
+
+        println!("Determined toolchain: {toolchain}\n");
+
+        let Ok(sysroot_src) = Path::new(toolchain)
+            .join("lib")
+            .join("rustlib")
+            .join("src")
+            .join("rust")
+            .join("library")
+            .into_os_string()
+            .into_string()
+        else {
+            bail!("The sysroot path is invalid UTF8");
+        };
+
+        Ok(Self {
+            sysroot_src,
+            crates: Vec::new(),
+        })
     }
 
     /// Write rust-project.json to disk
@@ -66,39 +100,4 @@ impl RustAnalyzerProject {
         }
         Ok(())
     }
-
-    /// Use `rustc` to determine the default toolchain
-    pub fn get_sysroot_src(&mut self) -> Result<(), Box<dyn Error>> {
-        // check if RUST_SRC_PATH is set
-        if let Ok(path) = env::var("RUST_SRC_PATH") {
-            self.sysroot_src = path;
-            return Ok(());
-        }
-
-        let toolchain = Command::new("rustc")
-            .arg("--print")
-            .arg("sysroot")
-            .output()?
-            .stdout;
-
-        let toolchain = String::from_utf8(toolchain)?;
-        let toolchain = toolchain.trim_end();
-
-        println!("Determined toolchain: {toolchain}\n");
-
-        let Ok(path) = Path::new(toolchain)
-            .join("lib")
-            .join("rustlib")
-            .join("src")
-            .join("rust")
-            .join("library")
-            .into_os_string()
-            .into_string()
-        else {
-            return Err("The sysroot path is invalid UTF8".into());
-        };
-        self.sysroot_src = path;
-
-        Ok(())
-    }
 }