Fix initialization

src/app_state.rs

@@ -4,6 +4,7 @@ use crossterm::{
     terminal::{Clear, ClearType},
     ExecutableCommand,
 };
+use serde::Deserialize;
 use std::{
     fs::{self, File},
     io::{Read, StdoutLock, Write},
@@ -32,6 +33,11 @@ pub enum StateFileStatus {
     NotRead,
 }
 
+#[derive(Deserialize)]
+struct CargoMetadata {
+    target_directory: PathBuf,
+}
+
 pub struct AppState {
     current_exercise_ind: usize,
     exercises: Vec<Exercise>,
@@ -91,8 +97,24 @@ impl AppState {
     pub fn new(
         exercise_infos: Vec<ExerciseInfo>,
         final_message: String,
-        target_dir: PathBuf,
-    ) -> (Self, StateFileStatus) {
+    ) -> Result<(Self, StateFileStatus)> {
+        let metadata_output = Command::new("cargo")
+            .arg("metadata")
+            .arg("-q")
+            .arg("--format-version")
+            .arg("1")
+            .arg("--no-deps")
+            .stdin(Stdio::null())
+            .stderr(Stdio::inherit())
+            .output()
+            .context(CARGO_METADATA_ERR)?
+            .stdout;
+        let target_dir = serde_json::de::from_slice::<CargoMetadata>(&metadata_output)
+            .context(
+                "Failed to read the field `target_directory` from the `cargo metadata` output",
+            )?
+            .target_directory;
+
         let exercises = exercise_infos
             .into_iter()
             .map(|mut exercise_info| {
@@ -134,7 +156,7 @@ impl AppState {
 
         let state_file_status = slf.update_from_file();
 
-        (slf, state_file_status)
+        Ok((slf, state_file_status))
     }
 
     #[inline]
@@ -388,6 +410,10 @@ impl AppState {
     }
 }
 
+const CARGO_METADATA_ERR: &str = "Failed to run the command `cargo metadata …`
+Did you already install Rust?
+Try running `cargo --version` to diagnose the problem.";
+
 const RERUNNING_ALL_EXERCISES_MSG: &[u8] = b"
 All exercises seem to be done.
 Recompiling and running all exercises to make sure that all of them are actually done.

src/main.rs

@@ -5,11 +5,10 @@ use crossterm::{
     terminal::{Clear, ClearType},
     ExecutableCommand,
 };
-use serde::Deserialize;
 use std::{
     io::{self, BufRead, Write},
-    path::{Path, PathBuf},
-    process::{exit, Command, Stdio},
+    path::Path,
+    process::exit,
 };
 
 use self::{app_state::AppState, dev::DevCommands, info_file::InfoFile, watch::WatchExit};
@@ -77,11 +76,6 @@ enum Subcommands {
     Dev(DevCommands),
 }
 
-#[derive(Deserialize)]
-struct CargoMetadata {
-    target_directory: PathBuf,
-}
-
 fn in_official_repo() -> bool {
     Path::new("dev/rustlings-repo.txt").exists()
 }
@@ -93,21 +87,6 @@ fn main() -> Result<()> {
         bail!("{OLD_METHOD_ERR}");
     }
 
-    let metadata_output = Command::new("cargo")
-        .arg("metadata")
-        .arg("-q")
-        .arg("--format-version")
-        .arg("1")
-        .arg("--no-deps")
-        .stdin(Stdio::null())
-        .stderr(Stdio::inherit())
-        .output()
-        .context(CARGO_METADATA_ERR)?
-        .stdout;
-    let target_dir = serde_json::de::from_slice::<CargoMetadata>(&metadata_output)
-        .context("Failed to read the field `target_directory` from the `cargo metadata` output")?
-        .target_directory;
-
     match args.command {
         Some(Subcommands::Init) => {
             if DEBUG_PROFILE {
@@ -142,8 +121,7 @@ fn main() -> Result<()> {
     let (mut app_state, state_file_status) = AppState::new(
         info_file.exercises,
         info_file.final_message.unwrap_or_default(),
-        target_dir,
-    );
+    )?;
 
     if let Some(welcome_message) = info_file.welcome_message {
         match state_file_status {
@@ -219,10 +197,6 @@ The new method doesn't include cloning the Rustlings' repository.
 Please follow the instructions in the README:
 https://github.com/rust-lang/rustlings#getting-started";
 
-const CARGO_METADATA_ERR: &str = "Failed to run the command `cargo metadata …`
-Did you already install Rust?
-Try running `cargo --version` to diagnose the problem.";
-
 const FORMAT_VERSION_HIGHER_ERR: &str =
     "The format version specified in the `info.toml` file is higher than the last one supported.
 It is possible that you have an outdated version of Rustlings.