Error handling in Rust is "some assembly required" -- error detail is available, and error handling models (early exit, bubble up, ignore) are supported, but there is not a well-accepted and complete convention for handling lower-level errors and bubbling u your own.

State of play

Best statement of currently recommended technique

• .map_err() and .map_ok()
• use this_error with some wrinkles

Examples of gaps in error model

tbs

To handle

• a standard error type for all your code

  • Capture arbitrary detail from lower level error
  • Cascadable, so if you return the type, your caller can do likewise

• deal with lower level crates that return crate-specific error type

• Support all the error handling possibilities:

  • anticipate specific error return and process it as an alternative success case
  • capture detail from error, add your own consequence of failure, bubble up to caller
  • use '?
  • use Err(Box (dyn Error)) (if Error trait has enough power)