Module err 

Error construction macros

These are specialized macros specific to this project’s patterns for throwing Errors; they make Error construction succinct and reduce clutter. They are developed from folding existing patterns into the macro while fixing several anti-patterns in the codebase.

• The primary macros Err! and err! are provided. Err! simply wraps err! in the Result variant to reduce Err(err!(...)) boilerplate, thus err! can be used in any case.

1. The macro makes the general Error construction easy: return Err!("something went wrong") replaces the prior return Err(Error::Err("something went wrong".to_owned())).

2. The macro integrates format strings automatically: return Err!("something bad: {msg}") replaces the prior return Err(Error::Err(format!("something bad: {msg}"))).

3. The macro scopes variants of Error: return Err!(Database("problem with bad database.")) replaces the prior return Err(Error::Database("problem with bad database.")).

4. The macro matches and scopes some special-case sub-variants, for example with ruma ErrorKind: return Err!(Request(MissingToken("you must provide an access token"))).

5. The macro fixes the anti-pattern of repeating messages in an error! log and then again in an Error construction, often slightly different due to the Error variant not supporting a format string. Instead return Err(Database(error!("problem with db: {msg}"))) logs the error at the callsite and then returns the error with the same string. Caller has the option of replacing error! with debug_error!.

Structs

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Functions

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