Add --require-solutions option to dev check

Cargo.lock

@@ -565,9 +565,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.83"
+version = "1.0.84"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b33eb56c327dec362a9e55b3ad14f9d2f0904fb5a5b03b513ab5465399e9f43"
+checksum = "ec96c6a92621310b51366f1e28d05ef11489516e93be030060e5fc12024a49d6"
 dependencies = [
  "unicode-ident",
 ]
@@ -705,18 +705,18 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "serde"
-version = "1.0.202"
+version = "1.0.203"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "226b61a0d411b2ba5ff6d7f73a476ac4f8bb900373459cd00fab8512828ba395"
+checksum = "7253ab4de971e72fb7be983802300c30b5a7f0c2e56fab8abfc6a214307c0094"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.202"
+version = "1.0.203"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6048858004bcff69094cd972ed40a32500f153bd3be9f716b2eed2e8217c4838"
+checksum = "500cbc0ebeb6f46627f50f3f5811ccf6bf00643be300b4c3eabc0ef55dc5b5ba"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1099,9 +1099,9 @@ checksum = "bec47e5bfd1bff0eeaf6d8b485cc1074891a197ab4225d504cb7a1ab88b02bf0"
 
 [[package]]
 name = "winnow"
-version = "0.6.8"
+version = "0.6.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3c52e9c97a68071b23e836c9380edae937f17b9c4667bd021973efc689f618d"
+checksum = "86c949fede1d13936a99f14fafd3e76fd642b556dd2ce96287fbe2e0151bfac6"
 dependencies = [
  "memchr",
 ]

Cargo.toml

@@ -20,7 +20,7 @@ license = "MIT"
 edition = "2021"
 
 [workspace.dependencies]
-serde = { version = "1.0.202", features = ["derive"] }
+serde = { version = "1.0.203", features = ["derive"] }
 toml_edit = { version = "0.22.13", default-features = false, features = ["parse", "serde"] }
 
 [package]

dev/Cargo.toml

@@ -1,101 +1,197 @@
 # 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 = "intro1_sol", path = "../solutions/00_intro/intro1.rs" },
   { name = "intro2", path = "../exercises/00_intro/intro2.rs" },
+  { name = "intro2_sol", path = "../solutions/00_intro/intro2.rs" },
   { name = "variables1", path = "../exercises/01_variables/variables1.rs" },
+  { name = "variables1_sol", path = "../solutions/01_variables/variables1.rs" },
   { name = "variables2", path = "../exercises/01_variables/variables2.rs" },
+  { name = "variables2_sol", path = "../solutions/01_variables/variables2.rs" },
   { name = "variables3", path = "../exercises/01_variables/variables3.rs" },
+  { name = "variables3_sol", path = "../solutions/01_variables/variables3.rs" },
   { name = "variables4", path = "../exercises/01_variables/variables4.rs" },
+  { name = "variables4_sol", path = "../solutions/01_variables/variables4.rs" },
   { name = "variables5", path = "../exercises/01_variables/variables5.rs" },
+  { name = "variables5_sol", path = "../solutions/01_variables/variables5.rs" },
   { name = "variables6", path = "../exercises/01_variables/variables6.rs" },
+  { name = "variables6_sol", path = "../solutions/01_variables/variables6.rs" },
   { name = "functions1", path = "../exercises/02_functions/functions1.rs" },
+  { name = "functions1_sol", path = "../solutions/02_functions/functions1.rs" },
   { name = "functions2", path = "../exercises/02_functions/functions2.rs" },
+  { name = "functions2_sol", path = "../solutions/02_functions/functions2.rs" },
   { name = "functions3", path = "../exercises/02_functions/functions3.rs" },
+  { name = "functions3_sol", path = "../solutions/02_functions/functions3.rs" },
   { name = "functions4", path = "../exercises/02_functions/functions4.rs" },
+  { name = "functions4_sol", path = "../solutions/02_functions/functions4.rs" },
   { name = "functions5", path = "../exercises/02_functions/functions5.rs" },
+  { name = "functions5_sol", path = "../solutions/02_functions/functions5.rs" },
   { name = "if1", path = "../exercises/03_if/if1.rs" },
+  { name = "if1_sol", path = "../solutions/03_if/if1.rs" },
   { name = "if2", path = "../exercises/03_if/if2.rs" },
+  { name = "if2_sol", path = "../solutions/03_if/if2.rs" },
   { name = "if3", path = "../exercises/03_if/if3.rs" },
+  { name = "if3_sol", path = "../solutions/03_if/if3.rs" },
   { name = "quiz1", path = "../exercises/quizzes/quiz1.rs" },
+  { name = "quiz1_sol", path = "../solutions/quizzes/quiz1.rs" },
   { name = "primitive_types1", path = "../exercises/04_primitive_types/primitive_types1.rs" },
+  { name = "primitive_types1_sol", path = "../solutions/04_primitive_types/primitive_types1.rs" },
   { name = "primitive_types2", path = "../exercises/04_primitive_types/primitive_types2.rs" },
+  { name = "primitive_types2_sol", path = "../solutions/04_primitive_types/primitive_types2.rs" },
   { name = "primitive_types3", path = "../exercises/04_primitive_types/primitive_types3.rs" },
+  { name = "primitive_types3_sol", path = "../solutions/04_primitive_types/primitive_types3.rs" },
   { name = "primitive_types4", path = "../exercises/04_primitive_types/primitive_types4.rs" },
+  { name = "primitive_types4_sol", path = "../solutions/04_primitive_types/primitive_types4.rs" },
   { name = "primitive_types5", path = "../exercises/04_primitive_types/primitive_types5.rs" },
+  { name = "primitive_types5_sol", path = "../solutions/04_primitive_types/primitive_types5.rs" },
   { name = "primitive_types6", path = "../exercises/04_primitive_types/primitive_types6.rs" },
+  { name = "primitive_types6_sol", path = "../solutions/04_primitive_types/primitive_types6.rs" },
   { name = "vecs1", path = "../exercises/05_vecs/vecs1.rs" },
+  { name = "vecs1_sol", path = "../solutions/05_vecs/vecs1.rs" },
   { name = "vecs2", path = "../exercises/05_vecs/vecs2.rs" },
+  { name = "vecs2_sol", path = "../solutions/05_vecs/vecs2.rs" },
   { name = "move_semantics1", path = "../exercises/06_move_semantics/move_semantics1.rs" },
+  { name = "move_semantics1_sol", path = "../solutions/06_move_semantics/move_semantics1.rs" },
   { name = "move_semantics2", path = "../exercises/06_move_semantics/move_semantics2.rs" },
+  { name = "move_semantics2_sol", path = "../solutions/06_move_semantics/move_semantics2.rs" },
   { name = "move_semantics3", path = "../exercises/06_move_semantics/move_semantics3.rs" },
+  { name = "move_semantics3_sol", path = "../solutions/06_move_semantics/move_semantics3.rs" },
   { name = "move_semantics4", path = "../exercises/06_move_semantics/move_semantics4.rs" },
+  { name = "move_semantics4_sol", path = "../solutions/06_move_semantics/move_semantics4.rs" },
   { name = "move_semantics5", path = "../exercises/06_move_semantics/move_semantics5.rs" },
+  { name = "move_semantics5_sol", path = "../solutions/06_move_semantics/move_semantics5.rs" },
   { name = "move_semantics6", path = "../exercises/06_move_semantics/move_semantics6.rs" },
+  { name = "move_semantics6_sol", path = "../solutions/06_move_semantics/move_semantics6.rs" },
   { name = "structs1", path = "../exercises/07_structs/structs1.rs" },
+  { name = "structs1_sol", path = "../solutions/07_structs/structs1.rs" },
   { name = "structs2", path = "../exercises/07_structs/structs2.rs" },
+  { name = "structs2_sol", path = "../solutions/07_structs/structs2.rs" },
   { name = "structs3", path = "../exercises/07_structs/structs3.rs" },
+  { name = "structs3_sol", path = "../solutions/07_structs/structs3.rs" },
   { name = "enums1", path = "../exercises/08_enums/enums1.rs" },
+  { name = "enums1_sol", path = "../solutions/08_enums/enums1.rs" },
   { name = "enums2", path = "../exercises/08_enums/enums2.rs" },
+  { name = "enums2_sol", path = "../solutions/08_enums/enums2.rs" },
   { name = "enums3", path = "../exercises/08_enums/enums3.rs" },
+  { name = "enums3_sol", path = "../solutions/08_enums/enums3.rs" },
   { name = "strings1", path = "../exercises/09_strings/strings1.rs" },
+  { name = "strings1_sol", path = "../solutions/09_strings/strings1.rs" },
   { name = "strings2", path = "../exercises/09_strings/strings2.rs" },
+  { name = "strings2_sol", path = "../solutions/09_strings/strings2.rs" },
   { name = "strings3", path = "../exercises/09_strings/strings3.rs" },
+  { name = "strings3_sol", path = "../solutions/09_strings/strings3.rs" },
   { name = "strings4", path = "../exercises/09_strings/strings4.rs" },
+  { name = "strings4_sol", path = "../solutions/09_strings/strings4.rs" },
   { name = "modules1", path = "../exercises/10_modules/modules1.rs" },
+  { name = "modules1_sol", path = "../solutions/10_modules/modules1.rs" },
   { name = "modules2", path = "../exercises/10_modules/modules2.rs" },
+  { name = "modules2_sol", path = "../solutions/10_modules/modules2.rs" },
   { name = "modules3", path = "../exercises/10_modules/modules3.rs" },
+  { name = "modules3_sol", path = "../solutions/10_modules/modules3.rs" },
   { name = "hashmaps1", path = "../exercises/11_hashmaps/hashmaps1.rs" },
+  { name = "hashmaps1_sol", path = "../solutions/11_hashmaps/hashmaps1.rs" },
   { name = "hashmaps2", path = "../exercises/11_hashmaps/hashmaps2.rs" },
+  { name = "hashmaps2_sol", path = "../solutions/11_hashmaps/hashmaps2.rs" },
   { name = "hashmaps3", path = "../exercises/11_hashmaps/hashmaps3.rs" },
+  { name = "hashmaps3_sol", path = "../solutions/11_hashmaps/hashmaps3.rs" },
   { name = "quiz2", path = "../exercises/quizzes/quiz2.rs" },
+  { name = "quiz2_sol", path = "../solutions/quizzes/quiz2.rs" },
   { name = "options1", path = "../exercises/12_options/options1.rs" },
+  { name = "options1_sol", path = "../solutions/12_options/options1.rs" },
   { name = "options2", path = "../exercises/12_options/options2.rs" },
+  { name = "options2_sol", path = "../solutions/12_options/options2.rs" },
   { name = "options3", path = "../exercises/12_options/options3.rs" },
+  { name = "options3_sol", path = "../solutions/12_options/options3.rs" },
   { name = "errors1", path = "../exercises/13_error_handling/errors1.rs" },
+  { name = "errors1_sol", path = "../solutions/13_error_handling/errors1.rs" },
   { name = "errors2", path = "../exercises/13_error_handling/errors2.rs" },
+  { name = "errors2_sol", path = "../solutions/13_error_handling/errors2.rs" },
   { name = "errors3", path = "../exercises/13_error_handling/errors3.rs" },
+  { name = "errors3_sol", path = "../solutions/13_error_handling/errors3.rs" },
   { name = "errors4", path = "../exercises/13_error_handling/errors4.rs" },
+  { name = "errors4_sol", path = "../solutions/13_error_handling/errors4.rs" },
   { name = "errors5", path = "../exercises/13_error_handling/errors5.rs" },
+  { name = "errors5_sol", path = "../solutions/13_error_handling/errors5.rs" },
   { name = "errors6", path = "../exercises/13_error_handling/errors6.rs" },
+  { name = "errors6_sol", path = "../solutions/13_error_handling/errors6.rs" },
   { name = "generics1", path = "../exercises/14_generics/generics1.rs" },
+  { name = "generics1_sol", path = "../solutions/14_generics/generics1.rs" },
   { name = "generics2", path = "../exercises/14_generics/generics2.rs" },
+  { name = "generics2_sol", path = "../solutions/14_generics/generics2.rs" },
   { name = "traits1", path = "../exercises/15_traits/traits1.rs" },
+  { name = "traits1_sol", path = "../solutions/15_traits/traits1.rs" },
   { name = "traits2", path = "../exercises/15_traits/traits2.rs" },
+  { name = "traits2_sol", path = "../solutions/15_traits/traits2.rs" },
   { name = "traits3", path = "../exercises/15_traits/traits3.rs" },
+  { name = "traits3_sol", path = "../solutions/15_traits/traits3.rs" },
   { name = "traits4", path = "../exercises/15_traits/traits4.rs" },
+  { name = "traits4_sol", path = "../solutions/15_traits/traits4.rs" },
   { name = "traits5", path = "../exercises/15_traits/traits5.rs" },
+  { name = "traits5_sol", path = "../solutions/15_traits/traits5.rs" },
   { name = "quiz3", path = "../exercises/quizzes/quiz3.rs" },
+  { name = "quiz3_sol", path = "../solutions/quizzes/quiz3.rs" },
   { name = "lifetimes1", path = "../exercises/16_lifetimes/lifetimes1.rs" },
+  { name = "lifetimes1_sol", path = "../solutions/16_lifetimes/lifetimes1.rs" },
   { name = "lifetimes2", path = "../exercises/16_lifetimes/lifetimes2.rs" },
+  { name = "lifetimes2_sol", path = "../solutions/16_lifetimes/lifetimes2.rs" },
   { name = "lifetimes3", path = "../exercises/16_lifetimes/lifetimes3.rs" },
+  { name = "lifetimes3_sol", path = "../solutions/16_lifetimes/lifetimes3.rs" },
   { name = "tests1", path = "../exercises/17_tests/tests1.rs" },
+  { name = "tests1_sol", path = "../solutions/17_tests/tests1.rs" },
   { name = "tests2", path = "../exercises/17_tests/tests2.rs" },
+  { name = "tests2_sol", path = "../solutions/17_tests/tests2.rs" },
   { name = "tests3", path = "../exercises/17_tests/tests3.rs" },
+  { name = "tests3_sol", path = "../solutions/17_tests/tests3.rs" },
   { name = "tests4", path = "../exercises/17_tests/tests4.rs" },
+  { name = "tests4_sol", path = "../solutions/17_tests/tests4.rs" },
   { name = "iterators1", path = "../exercises/18_iterators/iterators1.rs" },
+  { name = "iterators1_sol", path = "../solutions/18_iterators/iterators1.rs" },
   { name = "iterators2", path = "../exercises/18_iterators/iterators2.rs" },
+  { name = "iterators2_sol", path = "../solutions/18_iterators/iterators2.rs" },
   { name = "iterators3", path = "../exercises/18_iterators/iterators3.rs" },
+  { name = "iterators3_sol", path = "../solutions/18_iterators/iterators3.rs" },
   { name = "iterators4", path = "../exercises/18_iterators/iterators4.rs" },
+  { name = "iterators4_sol", path = "../solutions/18_iterators/iterators4.rs" },
   { name = "iterators5", path = "../exercises/18_iterators/iterators5.rs" },
+  { name = "iterators5_sol", path = "../solutions/18_iterators/iterators5.rs" },
   { name = "box1", path = "../exercises/19_smart_pointers/box1.rs" },
+  { name = "box1_sol", path = "../solutions/19_smart_pointers/box1.rs" },
   { name = "rc1", path = "../exercises/19_smart_pointers/rc1.rs" },
+  { name = "rc1_sol", path = "../solutions/19_smart_pointers/rc1.rs" },
   { name = "arc1", path = "../exercises/19_smart_pointers/arc1.rs" },
+  { name = "arc1_sol", path = "../solutions/19_smart_pointers/arc1.rs" },
   { name = "cow1", path = "../exercises/19_smart_pointers/cow1.rs" },
+  { name = "cow1_sol", path = "../solutions/19_smart_pointers/cow1.rs" },
   { name = "threads1", path = "../exercises/20_threads/threads1.rs" },
+  { name = "threads1_sol", path = "../solutions/20_threads/threads1.rs" },
   { name = "threads2", path = "../exercises/20_threads/threads2.rs" },
+  { name = "threads2_sol", path = "../solutions/20_threads/threads2.rs" },
   { name = "threads3", path = "../exercises/20_threads/threads3.rs" },
+  { name = "threads3_sol", path = "../solutions/20_threads/threads3.rs" },
   { name = "macros1", path = "../exercises/21_macros/macros1.rs" },
+  { name = "macros1_sol", path = "../solutions/21_macros/macros1.rs" },
   { name = "macros2", path = "../exercises/21_macros/macros2.rs" },
+  { name = "macros2_sol", path = "../solutions/21_macros/macros2.rs" },
   { name = "macros3", path = "../exercises/21_macros/macros3.rs" },
+  { name = "macros3_sol", path = "../solutions/21_macros/macros3.rs" },
   { name = "macros4", path = "../exercises/21_macros/macros4.rs" },
+  { name = "macros4_sol", path = "../solutions/21_macros/macros4.rs" },
   { name = "clippy1", path = "../exercises/22_clippy/clippy1.rs" },
+  { name = "clippy1_sol", path = "../solutions/22_clippy/clippy1.rs" },
   { name = "clippy2", path = "../exercises/22_clippy/clippy2.rs" },
+  { name = "clippy2_sol", path = "../solutions/22_clippy/clippy2.rs" },
   { name = "clippy3", path = "../exercises/22_clippy/clippy3.rs" },
+  { name = "clippy3_sol", path = "../solutions/22_clippy/clippy3.rs" },
   { name = "using_as", path = "../exercises/23_conversions/using_as.rs" },
+  { name = "using_as_sol", path = "../solutions/23_conversions/using_as.rs" },
   { name = "from_into", path = "../exercises/23_conversions/from_into.rs" },
+  { name = "from_into_sol", path = "../solutions/23_conversions/from_into.rs" },
   { name = "from_str", path = "../exercises/23_conversions/from_str.rs" },
+  { name = "from_str_sol", path = "../solutions/23_conversions/from_str.rs" },
   { name = "try_from_into", path = "../exercises/23_conversions/try_from_into.rs" },
+  { name = "try_from_into_sol", path = "../solutions/23_conversions/try_from_into.rs" },
   { name = "as_ref_mut", path = "../exercises/23_conversions/as_ref_mut.rs" },
+  { name = "as_ref_mut_sol", path = "../solutions/23_conversions/as_ref_mut.rs" },
 ]
 
 [package]

solutions/00_intro/intro1.rs

@@ -1,2 +1,5 @@
-// The exercise `intro1` only requires entering `n` in the terminal to go to the next exercise.
+fn main() {
-// It is just an introduction to how Rustlings works.
+    // Congratulations, you finished the first exercise 🎉
+    // As an introduction to Rustlings, the first exercise only required
+    // entering `n` in the terminal to go to the next exercise.
+}

src/app_state.rs

@@ -11,7 +11,7 @@ use std::{
 use crate::{
     clear_terminal,
     embedded::EMBEDDED_FILES,
-    exercise::{Exercise, OUTPUT_CAPACITY},
+    exercise::{Exercise, RunnableExercise, OUTPUT_CAPACITY},
     info_file::ExerciseInfo,
     DEBUG_PROFILE,
 };
@@ -40,6 +40,25 @@ struct CargoMetadata {
     target_directory: PathBuf,
 }
 
+pub fn parse_target_dir() -> Result<PathBuf> {
+    // Get the target directory from Cargo.
+    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;
+
+    serde_json::de::from_slice::<CargoMetadata>(&metadata_output)
+        .context("Failed to read the field `target_directory` from the `cargo metadata` output")
+        .map(|metadata| metadata.target_directory)
+}
+
 pub struct AppState {
     current_exercise_ind: usize,
     exercises: Vec<Exercise>,
@@ -104,23 +123,7 @@ impl AppState {
         exercise_infos: Vec<ExerciseInfo>,
         final_message: String,
     ) -> Result<(Self, StateFileStatus)> {
-        // Get the target directory from Cargo.
+        let target_dir = parse_target_dir()?;
-        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()
@@ -381,7 +384,7 @@ impl AppState {
             write!(writer, "Running {exercise} ... ")?;
             writer.flush()?;
 
-            let success = exercise.run(&mut output, &self.target_dir)?;
+            let success = exercise.run_exercise(&mut output, &self.target_dir)?;
             if !success {
                 writeln!(writer, "{}\n", "FAILED".red())?;
 

src/cargo_toml.rs

@@ -1,7 +1,11 @@
 use anyhow::{Context, Result};
+use std::path::Path;
 
 use crate::info_file::ExerciseInfo;
 
+/// Initial capacity of the bins buffer.
+pub const BINS_BUFFER_CAPACITY: usize = 1 << 14;
+
 /// Return the start and end index of the content of the list `bin = […]`.
 /// bin = [xxxxxxxxxxxxxxxxx]
 ///        |start_ind       |
@@ -40,6 +44,24 @@ pub fn append_bins(
         }
         buf.extend_from_slice(exercise_info.name.as_bytes());
         buf.extend_from_slice(b".rs\" },\n");
+
+        let sol_path = exercise_info.sol_path();
+        if !Path::new(&sol_path).exists() {
+            continue;
+        }
+
+        buf.extend_from_slice(b"  { name = \"");
+        buf.extend_from_slice(exercise_info.name.as_bytes());
+        buf.extend_from_slice(b"_sol");
+        buf.extend_from_slice(b"\", path = \"");
+        buf.extend_from_slice(exercise_path_prefix);
+        buf.extend_from_slice(b"solutions/");
+        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");
     }
 }
 
@@ -51,7 +73,7 @@ pub fn updated_cargo_toml(
 ) -> 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);
+    let mut updated_cargo_toml = Vec::with_capacity(BINS_BUFFER_CAPACITY);
     updated_cargo_toml.extend_from_slice(current_cargo_toml[..bins_start_ind].as_bytes());
     append_bins(
         &mut updated_cargo_toml,

src/cmd.rs

@@ -35,7 +35,7 @@ pub fn run_cmd(mut cmd: Command, description: &str, output: &mut Vec<u8>) -> Res
 pub struct CargoCmd<'a> {
     pub subcommand: &'a str,
     pub args: &'a [&'a str],
-    pub exercise_name: &'a str,
+    pub bin_name: &'a str,
     pub description: &'a str,
     /// RUSTFLAGS="-A warnings"
     pub hide_warnings: bool,
@@ -65,7 +65,7 @@ impl<'a> CargoCmd<'a> {
             .arg("always")
             .arg("-q")
             .arg("--bin")
-            .arg(self.exercise_name)
+            .arg(self.bin_name)
             .args(self.args);
 
         if self.hide_warnings {

src/dev.rs

@@ -19,7 +19,11 @@ pub enum DevCommands {
         no_git: bool,
     },
     /// Run checks on the exercises
-    Check,
+    Check {
+        /// Require that every exercise has a solution
+        #[arg(short, long)]
+        require_solutions: bool,
+    },
     /// Update the `Cargo.toml` file for the exercises
     Update,
 }
@@ -34,7 +38,7 @@ impl DevCommands {
 
                 new::new(&path, no_git).context(INIT_ERR)
             }
-            Self::Check => check::check(),
+            Self::Check { require_solutions } => check::check(require_solutions),
             Self::Update => update::update(),
         }
     }

src/dev/check.rs

@@ -1,20 +1,45 @@
-use anyhow::{anyhow, bail, Context, Error, Result};
+use anyhow::{anyhow, bail, Context, Result};
 use std::{
     cmp::Ordering,
     fs::{self, read_dir, OpenOptions},
-    io::Read,
+    io::{self, Read, Write},
     path::{Path, PathBuf},
 };
 
 use crate::{
-    cargo_toml::{append_bins, bins_start_end_ind},
+    app_state::parse_target_dir,
+    cargo_toml::{append_bins, bins_start_end_ind, BINS_BUFFER_CAPACITY},
+    exercise::{RunnableExercise, OUTPUT_CAPACITY},
     info_file::{ExerciseInfo, InfoFile},
     CURRENT_FORMAT_VERSION, DEBUG_PROFILE,
 };
 
 // Find a char that isn't allowed in the exercise's `name` or `dir`.
 fn forbidden_char(input: &str) -> Option<char> {
-    input.chars().find(|c| *c != '_' && !c.is_alphanumeric())
+    input.chars().find(|c| !c.is_alphanumeric() && *c != '_')
+}
+
+// Check that the Cargo.toml file is up-to-date.
+fn check_cargo_toml(
+    exercise_infos: &[ExerciseInfo],
+    current_cargo_toml: &str,
+    exercise_path_prefix: &[u8],
+) -> Result<()> {
+    let (bins_start_ind, bins_end_ind) = bins_start_end_ind(current_cargo_toml)?;
+
+    let old_bins = &current_cargo_toml.as_bytes()[bins_start_ind..bins_end_ind];
+    let mut new_bins = Vec::with_capacity(BINS_BUFFER_CAPACITY);
+    append_bins(&mut new_bins, exercise_infos, exercise_path_prefix);
+
+    if old_bins != new_bins {
+        if DEBUG_PROFILE {
+            bail!("The file `dev/Cargo.toml` is outdated. Please run `cargo run -- dev update` to update it");
+        }
+
+        bail!("The file `Cargo.toml` is outdated. Please run `rustlings dev update` to update it");
+    }
+
+    Ok(())
 }
 
 // Check the info of all exercises and return their paths in a set.
@@ -74,14 +99,19 @@ fn check_info_file_exercises(info_file: &InfoFile) -> Result<hashbrown::HashSet<
     Ok(paths)
 }
 
-// Check the `exercises` directory for unexpected files.
+// Check `dir` for unexpected files.
-fn check_unexpected_files(info_file_paths: &hashbrown::HashSet<PathBuf>) -> Result<()> {
+// Only Rust files in `allowed_rust_files` and `README.md` files are allowed.
-    fn unexpected_file(path: &Path) -> Error {
+// Only one level of directory nesting is allowed.
-        anyhow!("Found the file `{}`. Only `README.md` and Rust files related to an exercise in `info.toml` are allowed in the `exercises` directory", path.display())
+fn check_unexpected_files(
-    }
+    dir: &str,
+    allowed_rust_files: &hashbrown::HashSet<PathBuf>,
+) -> Result<()> {
+    let unexpected_file = |path: &Path| {
+        anyhow!("Found the file `{}`. Only `README.md` and Rust files related to an exercise in `info.toml` are allowed in the `{dir}` directory", path.display())
+    };
 
-    for entry in read_dir("exercises").context("Failed to open the `exercises` directory")? {
+    for entry in read_dir(dir).with_context(|| format!("Failed to open the `{dir}` directory"))? {
-        let entry = entry.context("Failed to read the `exercises` directory")?;
+        let entry = entry.with_context(|| format!("Failed to read the `{dir}` directory"))?;
 
         if entry.file_type().unwrap().is_file() {
             let path = entry.path();
@@ -90,7 +120,7 @@ fn check_unexpected_files(info_file_paths: &hashbrown::HashSet<PathBuf>) -> Resu
                 continue;
             }
 
-            if !info_file_paths.contains(&path) {
+            if !allowed_rust_files.contains(&path) {
                 return Err(unexpected_file(&path));
             }
 
@@ -114,7 +144,7 @@ fn check_unexpected_files(info_file_paths: &hashbrown::HashSet<PathBuf>) -> Resu
                 continue;
             }
 
-            if !info_file_paths.contains(&path) {
+            if !allowed_rust_files.contains(&path) {
                 return Err(unexpected_file(&path));
             }
         }
@@ -131,37 +161,48 @@ fn check_exercises(info_file: &InfoFile) -> Result<()> {
     }
 
     let info_file_paths = check_info_file_exercises(info_file)?;
-    check_unexpected_files(&info_file_paths)?;
+    check_unexpected_files("exercises", &info_file_paths)?;
 
     Ok(())
 }
 
-// Check that the Cargo.toml file is up-to-date.
+fn check_solutions(require_solutions: bool, info_file: &InfoFile) -> Result<()> {
-fn check_cargo_toml(
+    let mut paths = hashbrown::HashSet::with_capacity(info_file.exercises.len());
-    exercise_infos: &[ExerciseInfo],
+    let target_dir = parse_target_dir()?;
-    current_cargo_toml: &str,
+    let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
-    exercise_path_prefix: &[u8],
-) -> Result<()> {
-    let (bins_start_ind, bins_end_ind) = bins_start_end_ind(current_cargo_toml)?;
 
-    let old_bins = &current_cargo_toml.as_bytes()[bins_start_ind..bins_end_ind];
+    for exercise_info in &info_file.exercises {
-    let mut new_bins = Vec::with_capacity(1 << 13);
+        let path = exercise_info.sol_path();
-    append_bins(&mut new_bins, exercise_infos, exercise_path_prefix);
+        if !Path::new(&path).exists() {
-
+            if require_solutions {
-    if old_bins != new_bins {
+                bail!("Exercise {} is missing a solution", exercise_info.name);
-        if DEBUG_PROFILE {
-            bail!("The file `dev/Cargo.toml` is outdated. Please run `cargo run -- dev update` to update it");
             }
 
-        bail!("The file `Cargo.toml` is outdated. Please run `rustlings dev update` to update it");
+            // No solution to check.
+            continue;
         }
 
+        println!("Running the solution of {}", exercise_info.name);
+        let success = exercise_info.run_solution(&mut output, &target_dir)?;
+        if !success {
+            io::stderr().write_all(&output)?;
+
+            bail!(
+                "Failed to run the solution of the exercise {}",
+                exercise_info.name,
+            );
+        }
+
+        paths.insert(PathBuf::from(path));
+    }
+
+    check_unexpected_files("solutions", &paths)?;
+
     Ok(())
 }
 
-pub fn check() -> Result<()> {
+pub fn check(require_solutions: bool) -> Result<()> {
     let info_file = InfoFile::parse()?;
-    check_exercises(&info_file)?;
 
     // A hack to make `cargo run -- dev check` work when developing Rustlings.
     if DEBUG_PROFILE {
@@ -176,6 +217,9 @@ pub fn check() -> Result<()> {
         check_cargo_toml(&info_file.exercises, &current_cargo_toml, b"")?;
     }
 
+    check_exercises(&info_file)?;
+    check_solutions(require_solutions, &info_file)?;
+
     println!("\nEverything looks fine!");
 
     Ok(())

src/embedded.rs

@@ -1,6 +1,6 @@
 use anyhow::{Context, Error, Result};
 use std::{
-    fs::{create_dir, create_dir_all, OpenOptions},
+    fs::{create_dir, OpenOptions},
     io::{self, Write},
 };
 
@@ -43,8 +43,8 @@ struct ExerciseFiles {
 }
 
 // A directory in the `exercises/` directory.
-struct ExerciseDir {
+pub struct ExerciseDir {
-    name: &'static str,
+    pub name: &'static str,
     readme: &'static [u8],
 }
 
@@ -78,7 +78,7 @@ pub struct EmbeddedFiles {
     /// The content of the `info.toml` file.
     pub info_file: &'static str,
     exercise_files: &'static [ExerciseFiles],
-    exercise_dirs: &'static [ExerciseDir],
+    pub exercise_dirs: &'static [ExerciseDir],
 }
 
 impl EmbeddedFiles {
@@ -121,13 +121,9 @@ impl EmbeddedFiles {
 
         // 14 = 10 + 1 + 3
         // solutions/ + / + .rs
-        let mut dir_path = String::with_capacity(14 + dir.name.len() + exercise_name.len());
+        let mut solution_path = String::with_capacity(14 + dir.name.len() + exercise_name.len());
-        dir_path.push_str("solutions/");
+        solution_path.push_str("solutions/");
-        dir_path.push_str(dir.name);
+        solution_path.push_str(dir.name);
-        create_dir_all(&dir_path)
-            .with_context(|| format!("Failed to create the directory {dir_path}"))?;
-
-        let mut solution_path = dir_path;
         solution_path.push('/');
         solution_path.push_str(exercise_name);
         solution_path.push_str(".rs");

src/exercise.rs

@@ -17,30 +17,16 @@ use crate::{
 /// The initial capacity of the output buffer.
 pub const OUTPUT_CAPACITY: usize = 1 << 14;
 
-/// See `info_file::ExerciseInfo`
+// Run an exercise binary and append its output to the `output` buffer.
-pub struct Exercise {
+// Compilation must be done before calling this method.
-    pub dir: Option<&'static str>,
+fn run_bin(bin_name: &str, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
-    pub name: &'static str,
-    /// Path of the exercise file starting with the `exercises/` directory.
-    pub path: &'static str,
-    pub test: bool,
-    pub strict_clippy: bool,
-    pub hint: String,
-    pub done: bool,
-}
-
-impl Exercise {
-    // Run the exercise's binary and append its output to the `output` buffer.
-    // Compilation should be done before calling this method.
-    fn run_bin(&self, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
     writeln!(output, "{}", "Output".underlined())?;
 
     // 7 = "/debug/".len()
-        let mut bin_path =
+    let mut bin_path = PathBuf::with_capacity(target_dir.as_os_str().len() + 7 + bin_name.len());
-            PathBuf::with_capacity(target_dir.as_os_str().len() + 7 + self.name.len());
     bin_path.push(target_dir);
     bin_path.push("debug");
-        bin_path.push(self.name);
+    bin_path.push(bin_name);
 
     let success = run_cmd(Command::new(&bin_path), &bin_path.to_string_lossy(), output)?;
 
@@ -60,9 +46,38 @@ impl Exercise {
     Ok(success)
 }
 
-    /// Compile, check and run the exercise.
+/// See `info_file::ExerciseInfo`
-    /// The output is written to the `output` buffer after clearing it.
+pub struct Exercise {
-    pub fn run(&self, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
+    pub dir: Option<&'static str>,
+    pub name: &'static str,
+    /// Path of the exercise file starting with the `exercises/` directory.
+    pub path: &'static str,
+    pub test: bool,
+    pub strict_clippy: bool,
+    pub hint: String,
+    pub done: bool,
+}
+
+impl Exercise {
+    pub fn terminal_link(&self) -> StyledContent<TerminalFileLink<'_>> {
+        style(TerminalFileLink(self.path)).underlined().blue()
+    }
+}
+
+impl Display for Exercise {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        self.path.fmt(f)
+    }
+}
+
+pub trait RunnableExercise {
+    fn name(&self) -> &str;
+    fn strict_clippy(&self) -> bool;
+    fn test(&self) -> bool;
+
+    // Compile, check and run the exercise or its solution (depending on `bin_name´).
+    // The output is written to the `output` buffer after clearing it.
+    fn run(&self, bin_name: &str, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
         output.clear();
 
         // Developing the official Rustlings.
@@ -71,7 +86,7 @@ impl Exercise {
         let build_success = CargoCmd {
             subcommand: "build",
             args: &[],
-            exercise_name: self.name,
+            bin_name,
             description: "cargo build …",
             hide_warnings: false,
             target_dir,
@@ -87,7 +102,7 @@ impl Exercise {
         output.clear();
 
         // `--profile test` is required to also check code with `[cfg(test)]`.
-        let clippy_args: &[&str] = if self.strict_clippy {
+        let clippy_args: &[&str] = if self.strict_clippy() {
             &["--profile", "test", "--", "-D", "warnings"]
         } else {
             &["--profile", "test"]
@@ -95,7 +110,7 @@ impl Exercise {
         let clippy_success = CargoCmd {
             subcommand: "clippy",
             args: clippy_args,
-            exercise_name: self.name,
+            bin_name,
             description: "cargo clippy …",
             hide_warnings: false,
             target_dir,
@@ -107,14 +122,14 @@ impl Exercise {
             return Ok(false);
         }
 
-        if !self.test {
+        if !self.test() {
-            return self.run_bin(output, target_dir);
+            return run_bin(bin_name, output, target_dir);
         }
 
         let test_success = CargoCmd {
             subcommand: "test",
             args: &["--", "--color", "always", "--show-output"],
-            exercise_name: self.name,
+            bin_name,
             description: "cargo test …",
             // Hide warnings because they are shown by Clippy.
             hide_warnings: true,
@@ -124,18 +139,43 @@ impl Exercise {
         }
         .run()?;
 
-        let run_success = self.run_bin(output, target_dir)?;
+        let run_success = run_bin(bin_name, output, target_dir)?;
 
         Ok(test_success && run_success)
     }
 
-    pub fn terminal_link(&self) -> StyledContent<TerminalFileLink<'_>> {
+    /// Compile, check and run the exercise.
-        style(TerminalFileLink(self.path)).underlined().blue()
+    /// The output is written to the `output` buffer after clearing it.
+    #[inline]
+    fn run_exercise(&self, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
+        self.run(self.name(), output, target_dir)
+    }
+
+    /// Compile, check and run the exercise's solution.
+    /// The output is written to the `output` buffer after clearing it.
+    fn run_solution(&self, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
+        let name = self.name();
+        let mut bin_name = String::with_capacity(name.len());
+        bin_name.push_str(name);
+        bin_name.push_str("_sol");
+
+        self.run(&bin_name, output, target_dir)
     }
 }
 
-impl Display for Exercise {
+impl RunnableExercise for Exercise {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+    #[inline]
-        self.path.fmt(f)
+    fn name(&self) -> &str {
+        self.name
+    }
+
+    #[inline]
+    fn strict_clippy(&self) -> bool {
+        self.strict_clippy
+    }
+
+    #[inline]
+    fn test(&self) -> bool {
+        self.test
     }
 }

src/info_file.rs

@@ -2,7 +2,7 @@ use anyhow::{bail, Context, Error, Result};
 use serde::Deserialize;
 use std::{fs, io::ErrorKind};
 
-use crate::embedded::EMBEDDED_FILES;
+use crate::{embedded::EMBEDDED_FILES, exercise::RunnableExercise};
 
 /// Deserialized from the `info.toml` file.
 #[derive(Deserialize)]
@@ -49,6 +49,47 @@ impl ExerciseInfo {
 
         path
     }
+
+    /// Path to the solution file starting with the `solutions/` directory.
+    pub fn sol_path(&self) -> String {
+        let mut path = if let Some(dir) = &self.dir {
+            // 14 = 10 + 1 + 3
+            // solutions/ + / + .rs
+            let mut path = String::with_capacity(14 + dir.len() + self.name.len());
+            path.push_str("solutions/");
+            path.push_str(dir);
+            path.push('/');
+            path
+        } else {
+            // 13 = 10 + 3
+            // solutions/ + .rs
+            let mut path = String::with_capacity(13 + self.name.len());
+            path.push_str("solutions/");
+            path
+        };
+
+        path.push_str(&self.name);
+        path.push_str(".rs");
+
+        path
+    }
+}
+
+impl RunnableExercise for ExerciseInfo {
+    #[inline]
+    fn name(&self) -> &str {
+        &self.name
+    }
+
+    #[inline]
+    fn strict_clippy(&self) -> bool {
+        self.strict_clippy
+    }
+
+    #[inline]
+    fn test(&self) -> bool {
+        self.test
+    }
 }
 
 /// The deserialized `info.toml` file.

src/init.rs

@@ -34,6 +34,20 @@ pub fn init() -> Result<()> {
         .init_exercises_dir(&info_file.exercises)
         .context("Failed to initialize the `rustlings/exercises` directory")?;
 
+    create_dir("solutions").context("Failed to create the `solutions/` directory")?;
+    for dir in EMBEDDED_FILES.exercise_dirs {
+        let mut dir_path = String::with_capacity(10 + dir.name.len());
+        dir_path.push_str("solutions/");
+        dir_path.push_str(dir.name);
+        create_dir(&dir_path)
+            .with_context(|| format!("Failed to create the directory {dir_path}"))?;
+    }
+    for exercise_info in &info_file.exercises {
+        let solution_path = exercise_info.sol_path();
+        fs::write(&solution_path, INIT_SOLUTION_FILE)
+            .with_context(|| format!("Failed to create the file {solution_path}"))?;
+    }
+
     let current_cargo_toml = include_str!("../dev-Cargo.toml");
     // Skip the first line (comment).
     let newline_ind = current_cargo_toml
@@ -72,6 +86,12 @@ pub fn init() -> Result<()> {
     Ok(())
 }
 
+const INIT_SOLUTION_FILE: &[u8] = b"fn main() {
+    // DON'T EDIT THIS SOLUTION FILE!
+    // It will be automatically filled after you finish the exercise.
+}
+";
+
 const GITIGNORE: &[u8] = b".rustlings-state.txt
 solutions
 Cargo.lock

src/run.rs

@@ -4,14 +4,14 @@ use std::io::{self, Write};
 
 use crate::{
     app_state::{AppState, ExercisesProgress},
-    exercise::OUTPUT_CAPACITY,
+    exercise::{RunnableExercise, OUTPUT_CAPACITY},
     terminal_link::TerminalFileLink,
 };
 
 pub fn run(app_state: &mut AppState) -> Result<()> {
     let exercise = app_state.current_exercise();
     let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
-    let success = exercise.run(&mut output, app_state.target_dir())?;
+    let success = exercise.run_exercise(&mut output, app_state.target_dir())?;
 
     let mut stdout = io::stdout().lock();
     stdout.write_all(&output)?;

src/watch/state.rs

@@ -8,7 +8,7 @@ use std::io::{self, StdoutLock, Write};
 use crate::{
     app_state::{AppState, ExercisesProgress},
     clear_terminal,
-    exercise::OUTPUT_CAPACITY,
+    exercise::{RunnableExercise, OUTPUT_CAPACITY},
     progress_bar::progress_bar,
     terminal_link::TerminalFileLink,
 };
@@ -54,7 +54,7 @@ impl<'a> WatchState<'a> {
         let success = self
             .app_state
             .current_exercise()
-            .run(&mut self.output, self.app_state.target_dir())?;
+            .run_exercise(&mut self.output, self.app_state.target_dir())?;
         if success {
             self.done_status =
                 if let Some(solution_path) = self.app_state.current_solution_path()? {