Release v0.5.0

Breaking Changes - 0.5.0

• GroupContext::message() now combines all available fields:

  • Before: Displayed only the first available field in priority order (message → location → tags → metadata)

  • After: Combines all fields into one cohesive unit with format [tag1, tag2] at file:line: message (key1=value1, key2=value2)

  • Rationale: Improves readability by presenting each context as a unified information unit rather than fragmented parts separated by "->" arrows

  • Migration: Code parsing ErrorContext::message() output needs to be updated to handle the new combined format. Single-field contexts remain unchanged.

  • Recommended: Use ErrorContext::builder() to create grouped contexts that display as cohesive units in error chains:

    // Before: Multiple separate contexts
    
    err.with_context(tag!("database"))
    
       .with_context(location!())
    
       .with_context(metadata!("host", "localhost"))
    
    // Output: -> [database] -> at main.rs:42 -> (host=localhost)
    
    
    
    // After: Single grouped context  
    
    err.with_context(ErrorContext::builder()
    
        .tag("database")
    
        .location(file!(), line!())
    
        .metadata("host", "localhost")
    
        .build())
    
    // Output: -> [database] at main.rs:42 (host=localhost)

Added - 0.5.0

• ResultExt trait: New ergonomic extension trait for adding context to Result types

  • .ctx(msg) - Add static context message

  • .ctx_with(|| format!(...)) - Add lazily-evaluated context (2.1x faster on success)

• BoxedResultExt trait: Chain contexts on already-boxed ComposableError results

  • .ctx_boxed(msg) - Add context to boxed error

  • .ctx_boxed_with(|| ...) - Add lazy context to boxed error

• prelude module: Convenient re-exports for quick starts

  • Import everything with use error_rail::prelude::*;

  • Includes BoxedResult<T, E> type alias for ergonomic return types

Changed - 0.5.0

• Removed redundant type aliases: SimpleComposableError<E> and TaggedComposableError<E> have been completely removed

  • Rationale: These aliases provided no additional functionality over ComposableError<E> and created unnecessary complexity

  • Migration: Use ComposableError<E> directly - these were simple type aliases with no behavior change

  • Impact: Code using these aliases will need to be updated to use ComposableError<E> instead

• Enhanced error messages: Added #[diagnostic::on_unimplemented] to IntoErrorContext trait for better compiler guidance when trait bounds are not satisfied

• Improved DX: Added helpful implementation examples and links to documentation in trait documentation

• Deprecated individual context macros: location!(), tag!(), and metadata!() macros are now deprecated in favor of the new group! macro

  • Rationale: The new group! macro provides lazy evaluation for grouped contexts, combining multiple fields into a single cohesive unit while maintaining performance benefits

  • Migration: Replace individual macro calls with function-call style group!():

    // Before: Multiple separate contexts (eager allocation)
    
    err.with_context(location!())
    
       .with_context(tag!("database"))
    
       .with_context(metadata!("host", "localhost"));
    
    // Output: -> at main.rs:42 -> [database] -> (host=localhost)
    
    
    
    // After: Single grouped context (lazy evaluation)
    
    err.with_context(group!(
    
        location(file!(), line!()),
    
        tag("database"),
    
        metadata("host", "localhost")
    
    ));
    
    // Output: -> [database] at main.rs:42 (host=localhost)

  • Benefits:

    • Lazy evaluation: No string formatting until error occurs

    • Unified display: All fields appear as one cohesive context unit

    • Better performance: Reduced allocations on success paths

  • Removal timeline: Deprecated macros will be removed in version 0.6.0

  • New exports: group! macro and LazyGroupContext type added to prelude

Deprecated - 0.5.0

• location!(), tag!(), and metadata!() macros - Use group! macro instead (scheduled for removal in 0.6.0)

Removed - 0.5.0

• SimpleComposableError<E> - Use ComposableError<E> directly (completely removed)

• TaggedComposableError<E> - Use ComposableError<E> with ErrorContext::tag() instead (completely removed)