Merge branch 'mr/494-create-lab-for-module-error-handling-2' into 'master'

Resolve "Create Lab for Module: Error Handling"

Closes #494

See merge request feng/training/material!585

Author: Dana Binkley

courses/rust_essentials/200_error_handling/88-error_handling.lab.rst

@@ -2,8 +2,16 @@
 Lab
 =====
 
------
-TBD
------
+------------------
+Lab Instructions
+------------------
 
-TBD
+- Solve for compilation errors
+
+- Follow the hints!
+
+- Success is
+
+    - Code that compiles
+
+    - ...and that follows any behavior indicated within the hints!

courses/rust_essentials/200_error_handling/lab/answer/Cargo.toml

@@ -1,7 +1,8 @@
 [package]
-name = "lab"
+name = "answer"
 version = "1.0.0"
 edition = "2024"
 
 [dependencies]
-# Leave this empty for now
+anyhow = "*"
+thiserror = "*"

courses/rust_essentials/200_error_handling/lab/answer/src/main.rs

@@ -1,3 +1,99 @@
+//! Lab (answer)
+//! Error Handling
+//!
+
+#![allow(unused_assignments)]
+#![allow(unused_variables)]
+#![allow(dead_code)]
+
 fn main() {
-    println!("TBD");
+    // TASK 1 - Error Result
+    // Hint: You can return an error using a 'Result' enum variant 'Err' 
+    enum Reason { TooYoung, TooOld, }
+    fn check_age(age: i32) -> Result<i32, Reason> {
+        if age < 18 {
+            Err(Reason::TooYoung)
+        } else {
+            Ok(age)
+        }
+    }
+    let my_age = 17;
+
+    // TASK 2 - Handling Results
+    // Hint: Replace the 'unwrap()' function by a pattern matching to 'handle check_age' return
+    match check_age(my_age) {
+        Ok(age) => println!("Access granted! You are {} years old.", age),
+        Err(Reason::TooYoung) => println!("Sorry, you're not old enough yet."),
+        Err(Reason::TooOld) => println!("System error: User exceeds maximum age limit."),
+    }
+    
+    // TASK 3 - The Try Operator
+    // Hint: Use the try operator to return an error automatically to the caller of 'register' 
+    // if check_age returns an error
+    // The try operator tries to convert 'reason' to the return type of 'register' 'string'
+    // From trait should be implemented
+    impl From<Reason> for String {
+        fn from(reason: Reason) -> Self {
+            match reason {
+                Reason::TooYoung => "User is under the required age limit".to_string(),
+                Reason::TooOld => "User is above the maximum age limit".to_string(),
+            }
+        }
+    }
+    fn register() -> Result<(), String> {
+        check_age(10)?;
+        Ok(())
+    }  
+
+    // TASK 4 - Handling Propagation
+    // Hint: Error has been propagated from 'check_age' to 'register' to 'main'
+    // Use pattern matching to handle return from 'register' instead of 'unwrap()'
+    // Print a message for each possible result
+    match register() {
+        Ok(_) => println!("Registration successful!"),
+        Err(e) => println!("Registration failed: {}", e),
+    }
+    
+    // TASK 5 - thiserror
+    // Hint: Convert the comments over the two variants into error text using 'thiserror'
+    // Then make sure withdraw returns an 'AccountError' of 'InsufficientFunds' 
+    // Display the 'balance' and the 'amount'
+    use thiserror::Error;
+    #[derive(Error, Debug)]
+    pub enum AccountError {
+        #[error("insufficient funds: available {available}, requested {requested}")]
+        InsufficientFunds { available: u64, requested: u64 },
+        #[error("account is inactive")]
+        InactiveAccount,
+    }
+    fn withdraw(balance: u64, amount: u64) -> Result<u64, AccountError> {
+        if amount > balance {
+            return Err(AccountError::InsufficientFunds { 
+                available: balance, 
+                requested: amount 
+            });
+        }
+        Ok(balance - amount)
+    }
+
+    // Task 6 - Anyhow
+    // Hint: Turn the 'println' in 'process_transaction' into an additional context of information
+    // Attached to the withdraw function
+    // You have to use the correct library to be able to use the 'with_context' method
+    use anyhow::Context;
+    fn process_transaction(balance: u64, amount: u64) -> anyhow::Result<()> {
+        withdraw(balance, amount)
+            .with_context(|| format!("Failed to process withdrawal of ${}", amount))?;
+        Ok(())
+    }
+    let result = process_transaction(50, 100);
+    if let Err(e) = result {
+        // This will print a message that looks like an actual run-time error
+        println!("Error: {}", e); 
+        // This next line will print the following :
+        // Debug Trace: Failed to process withdrawal of $100
+        // Caused by:
+        // insufficient funds: available 50, requested 100
+        println!("\nDebug Trace: {:?}", e);
+    }
 }

courses/rust_essentials/200_error_handling/lab/prompt/Cargo.toml

@@ -1,7 +1,8 @@
 [package]
-name = "lab"
+name = "prompt"
 version = "1.0.0"
 edition = "2024"
 
 [dependencies]
-# Leave this empty for now
+anyhow = "*"
+thiserror = "*"

courses/rust_essentials/200_error_handling/lab/prompt/src/main.rs

@@ -1,3 +1,86 @@
+//! Lab (prompt)
+//! Error Handling
+//!
+//! Fix all the compile errors below and/or follow the hints provided
+//!
+
+#![allow(unused_assignments)]
+#![allow(unused_variables)]
+#![allow(dead_code)]
+
 fn main() {
-    println!("TBD");
+    // TASK 1 - Error Result
+    // Hint: You can return an error using a 'Result' enum variant 'Err' 
+    enum Reason { TooYoung, TooOld, }
+    fn check_age(age: i32) -> Result<i32, Reason> {
+        todo!("Replace me with a proper error result");
+    }
+    let my_age = 17;
+
+    // TASK 2 - Handling Results
+    // Hint: Replace the 'unwrap()' function by a pattern matching to 'handle check_age' return
+    check_age(my_age).unwrap();
+    
+    // TASK 3 - the Try Operator
+    // Hint: Use the try operator to return an error automatically to the caller of 'register'
+    // if check_age returns an error
+    // The try operator tries to convert 'reason' to the return type of 'register' 'string'
+    // From trait should be implemented
+    impl From<Reason> for String {
+        fn from(reason: Reason) -> Self {
+            match reason {
+                Reason::TooYoung => "User is under the required age limit".to_string(),
+                Reason::TooOld => "User is above the maximum age limit".to_string(),
+            }
+        }
+    }
+    fn register() -> Result<(), String> {
+        check_age(10);
+        Ok(())
+    }
+
+    // TASK 4 - Handling Propagation
+    // Hint: Error has been propagated from 'check_age' to 'register' to 'main'
+    // Use pattern matching to handle return from 'register' instead of 'unwrap()'
+    // Print a message for each possible result
+    register().unwrap();
+    
+    // TASK 5 - thiserror
+    // Hint: Convert the comments over the two variants into error text using 'thiserror'
+    // Then make sure withdraw returns an 'AccountError' of 'InsufficientFunds' 
+    // Display the 'balance' and the 'amount'
+    use thiserror::Error;
+    #[derive(Error, Debug)]
+    pub enum AccountError {
+        // Insufficient funds: available {available}, requested {requested} 
+        InsufficientFunds { available: u64, requested: u64 },
+        // Account is inactive 
+        InactiveAccount,
+    }
+    fn withdraw(balance: u64, amount: u64) -> Result<u64, AccountError> {
+        if amount > balance {
+            return Err(AccountError{});
+        }
+        Ok(balance - amount)
+    }
+    
+    // Task 6 - Anyhow
+    // Hint: Turn the 'println' in 'process_transaction' into an additional context of information
+    // Attached to the 'withdraw' function
+    // You have to use the correct library to be able to use the 'with_context' method
+    fn process_transaction(balance: u64, amount: u64) -> anyhow::Result<()> {
+        withdraw(balance, amount)
+        println!("Failed to process withdrawal of ${}", amount);
+        Ok(())
+    }
+    let result = process_transaction(50, 100);
+    if let Err(e) = result {
+        // This will print a message that looks like an actual run-time error
+        println!("Error: {}", e); 
+        // This next line will print the following :
+        // Debug Trace: Failed to process withdrawal of $100
+        // Caused by:
+        // insufficient funds: available 50, requested 100
+        println!("\nDebug Trace: {:?}", e);
+    } 
 }