Fix the generated Cargo.toml after rustlings init

dev/Cargo.toml

@@ -1,4 +1,4 @@
-# Don't edit the `bin` list manually! It is updated by `cargo run -- dev update`
+# Don't edit the `bin` list manually! It is updated by `cargo run -- dev update`. This comment line will be stripped in `rustlings init`.
 bin = [
   { name = "intro1", path = "../exercises/00_intro/intro1.rs" },
   { name = "intro2", path = "../exercises/00_intro/intro2.rs" },

src/cargo_toml.rs

@@ -0,0 +1,57 @@
+use anyhow::{Context, Result};
+
+use crate::info_file::ExerciseInfo;
+
+pub fn bins_start_end_ind(cargo_toml: &str) -> Result<(usize, usize)> {
+    let start_ind = cargo_toml
+        .find("bin = [")
+        .context("Failed to find the start of the `bin` list (`bin = [`)")?
+        + 7;
+    let end_ind = start_ind
+        + cargo_toml
+            .get(start_ind..)
+            .and_then(|slice| slice.as_bytes().iter().position(|c| *c == b']'))
+            .context("Failed to find the end of the `bin` list (`]`)")?;
+
+    Ok((start_ind, end_ind))
+}
+
+pub fn append_bins(
+    buf: &mut Vec<u8>,
+    exercise_infos: &[ExerciseInfo],
+    exercise_path_prefix: &[u8],
+) {
+    buf.push(b'\n');
+    for exercise_info in exercise_infos {
+        buf.extend_from_slice(b"  { name = \"");
+        buf.extend_from_slice(exercise_info.name.as_bytes());
+        buf.extend_from_slice(b"\", path = \"");
+        buf.extend_from_slice(exercise_path_prefix);
+        buf.extend_from_slice(b"exercises/");
+        if let Some(dir) = &exercise_info.dir {
+            buf.extend_from_slice(dir.as_bytes());
+            buf.push(b'/');
+        }
+        buf.extend_from_slice(exercise_info.name.as_bytes());
+        buf.extend_from_slice(b".rs\" },\n");
+    }
+}
+
+pub fn updated_cargo_toml(
+    exercise_infos: &[ExerciseInfo],
+    current_cargo_toml: &str,
+    exercise_path_prefix: &[u8],
+) -> Result<Vec<u8>> {
+    let (bins_start_ind, bins_end_ind) = bins_start_end_ind(current_cargo_toml)?;
+
+    let mut updated_cargo_toml = Vec::with_capacity(1 << 13);
+    updated_cargo_toml.extend_from_slice(current_cargo_toml[..bins_start_ind].as_bytes());
+    append_bins(
+        &mut updated_cargo_toml,
+        exercise_infos,
+        exercise_path_prefix,
+    );
+    updated_cargo_toml.extend_from_slice(current_cargo_toml[bins_end_ind..].as_bytes());
+
+    Ok(updated_cargo_toml)
+}

src/dev/check.rs

@@ -7,6 +7,7 @@ use std::{
 };
 
 use crate::{
+    cargo_toml::{append_bins, bins_start_end_ind},
     info_file::{ExerciseInfo, InfoFile},
     CURRENT_FORMAT_VERSION, DEBUG_PROFILE,
 };
@@ -136,41 +137,6 @@ fn check_exercises(info_file: &InfoFile) -> Result<()> {
     Ok(())
 }
 
-pub fn bins_start_end_ind(cargo_toml: &str) -> Result<(usize, usize)> {
-    let start_ind = cargo_toml
-        .find("bin = [")
-        .context("Failed to find the start of the `bin` list (`bin = [`)")?
-        + 7;
-    let end_ind = start_ind
-        + cargo_toml
-            .get(start_ind..)
-            .and_then(|slice| slice.as_bytes().iter().position(|c| *c == b']'))
-            .context("Failed to find the end of the `bin` list (`]`)")?;
-
-    Ok((start_ind, end_ind))
-}
-
-pub fn append_bins(
-    buf: &mut Vec<u8>,
-    exercise_infos: &[ExerciseInfo],
-    exercise_path_prefix: &[u8],
-) {
-    buf.push(b'\n');
-    for exercise_info in exercise_infos {
-        buf.extend_from_slice(b"  { name = \"");
-        buf.extend_from_slice(exercise_info.name.as_bytes());
-        buf.extend_from_slice(b"\", path = \"");
-        buf.extend_from_slice(exercise_path_prefix);
-        buf.extend_from_slice(b"exercises/");
-        if let Some(dir) = &exercise_info.dir {
-            buf.extend_from_slice(dir.as_bytes());
-            buf.push(b'/');
-        }
-        buf.extend_from_slice(exercise_info.name.as_bytes());
-        buf.extend_from_slice(b".rs\" },\n");
-    }
-}
-
 fn check_cargo_toml(
     exercise_infos: &[ExerciseInfo],
     current_cargo_toml: &str,
@@ -183,7 +149,13 @@ fn check_cargo_toml(
     append_bins(&mut new_bins, exercise_infos, exercise_path_prefix);
 
     if old_bins != new_bins {
-        bail!("`Cargo.toml` is outdated. Run `rustlings dev update` to update it");
+        if DEBUG_PROFILE {
+            bail!("The file `dev/Cargo.toml` is outdated. Please run `cargo run -- dev update` to update it");
+        } else {
+            bail!(
+                "The file `Cargo.toml` is outdated. Please run `rustlings dev update` to update it",
+            );
+        }
     }
 
     Ok(())
@@ -198,14 +170,11 @@ pub fn check() -> Result<()> {
             &info_file.exercises,
             include_str!("../../dev/Cargo.toml"),
             b"../",
-        )
-        .context("The file `dev/Cargo.toml` is outdated. Please run `cargo run -- dev update` to update it")?;
+        )?;
     } else {
         let current_cargo_toml =
             fs::read_to_string("Cargo.toml").context("Failed to read the file `Cargo.toml`")?;
-        check_cargo_toml(&info_file.exercises, &current_cargo_toml, b"").context(
-            "The file `Cargo.toml` is outdated. Please run `rustlings dev update` to update it",
-        )?;
+        check_cargo_toml(&info_file.exercises, &current_cargo_toml, b"")?;
     }
 
     println!("\nEverything looks fine!");

src/dev/update.rs

@@ -3,26 +3,22 @@ use std::fs;
 use anyhow::{Context, Result};
 
 use crate::{
+    cargo_toml::updated_cargo_toml,
     info_file::{ExerciseInfo, InfoFile},
     DEBUG_PROFILE,
 };
 
-use super::check::{append_bins, bins_start_end_ind};
-
 fn update_cargo_toml(
     exercise_infos: &[ExerciseInfo],
     current_cargo_toml: &str,
-    cargo_toml_path: &str,
     exercise_path_prefix: &[u8],
+    cargo_toml_path: &str,
 ) -> Result<()> {
-    let (bins_start_ind, bins_end_ind) = bins_start_end_ind(current_cargo_toml)?;
+    let updated_cargo_toml =
+        updated_cargo_toml(exercise_infos, current_cargo_toml, exercise_path_prefix)?;
 
-    let mut new_cargo_toml = Vec::with_capacity(1 << 13);
-    new_cargo_toml.extend_from_slice(current_cargo_toml[..bins_start_ind].as_bytes());
-    append_bins(&mut new_cargo_toml, exercise_infos, exercise_path_prefix);
-    new_cargo_toml.extend_from_slice(current_cargo_toml[bins_end_ind..].as_bytes());
-
-    fs::write(cargo_toml_path, new_cargo_toml).context("Failed to write the `Cargo.toml` file")?;
+    fs::write(cargo_toml_path, updated_cargo_toml)
+        .context("Failed to write the `Cargo.toml` file")?;
 
     Ok(())
 }
@@ -34,8 +30,8 @@ pub fn update() -> Result<()> {
         update_cargo_toml(
             &info_file.exercises,
             include_str!("../../dev/Cargo.toml"),
-            "dev/Cargo.toml",
             b"../",
+            "dev/Cargo.toml",
         )
         .context("Failed to update the file `dev/Cargo.toml`")?;
 
@@ -43,7 +39,7 @@ pub fn update() -> Result<()> {
     } else {
         let current_cargo_toml =
             fs::read_to_string("Cargo.toml").context("Failed to read the file `Cargo.toml`")?;
-        update_cargo_toml(&info_file.exercises, &current_cargo_toml, "Cargo.toml", b"")
+        update_cargo_toml(&info_file.exercises, &current_cargo_toml, b"", "Cargo.toml")
             .context("Failed to update the file `Cargo.toml`")?;
 
         println!("Updated `Cargo.toml`");

src/init.rs

@@ -6,17 +6,7 @@ use std::{
     path::Path,
 };
 
-use crate::embedded::EMBEDDED_FILES;
-
-const CARGO_TOML: &[u8] = {
-    let cargo_toml = include_bytes!("../dev/Cargo.toml");
-    // Skip the first line (comment).
-    let mut start_ind = 0;
-    while cargo_toml[start_ind] != b'\n' {
-        start_ind += 1;
-    }
-    cargo_toml.split_at(start_ind + 1).1
-};
+use crate::{cargo_toml::updated_cargo_toml, embedded::EMBEDDED_FILES, info_file::InfoFile};
 
 pub fn init() -> Result<()> {
     if Path::new("exercises").is_dir() && Path::new("Cargo.toml").is_file() {
@@ -38,7 +28,19 @@ pub fn init() -> Result<()> {
         .init_exercises_dir()
         .context("Failed to initialize the `rustlings/exercises` directory")?;
 
-    fs::write("Cargo.toml", CARGO_TOML)
+    let info_file = InfoFile::parse()?;
+    let current_cargo_toml = include_str!("../dev/Cargo.toml");
+    // Skip the first line (comment).
+    let newline_ind = current_cargo_toml
+        .as_bytes()
+        .iter()
+        .position(|c| *c == b'\n')
+        .context("The embedded `Cargo.toml` is empty or contains only one line.")?;
+    let current_cargo_toml =
+        &current_cargo_toml[(newline_ind + 1).min(current_cargo_toml.len() - 1)..];
+    let updated_cargo_toml = updated_cargo_toml(&info_file.exercises, current_cargo_toml, b"")
+        .context("Failed to generate `Cargo.toml`")?;
+    fs::write("Cargo.toml", updated_cargo_toml)
         .context("Failed to create the file `rustlings/Cargo.toml`")?;
 
     fs::write(".gitignore", GITIGNORE)

src/main.rs

@@ -14,6 +14,7 @@ use std::{
 use self::{app_state::AppState, dev::DevCommands, info_file::InfoFile, watch::WatchExit};
 
 mod app_state;
+mod cargo_toml;
 mod dev;
 mod embedded;
 mod exercise;