Small crate to handle errors and results more easily. Simply include it in the dependencies section using the latest available version and enable the features that will include mapped errors from different crates.
The features for this crate are determined by the external crates supported. If you want to use the mapping for tokio
for example, add the feature "tokio", the same way with chrono, or any other crate you want to map.
The only error support that'll be loaded by default and cannot be disabled is the support for std Rust errors.
To use only the functions and the TheResult type, add to dependencies with no features, and to include mapping for every
crate available, use the full feature.
The result enum is a customized TheResult type, which is an alias for Result<T, TheError>, where TheError is a struct type containing the following members:
Rust
pub struct TheError {
pub error: TheErrorType,
pub file: String,
pub location: String,
pub datestamp: String,
pub timestamp: String
}
Where the error member of type TheErrorType is a struct containing:
Rust
pub struct TheErrorType {
pub error_type: SystemErrorCodes,
pub error_content: String,
}
SystemErrorCodes is an enum type that contains all the possible error types with a good degree of precision. It's
bound to keep growing as more crates are added to error_mapper.
This crate implements the std::fmt::Display trait for all its error data types. The output result of the fully
displayed error will be similar to the following example:
src\data\db_conn.rs 9:23 @ 2023-09-02::22:26:40 -> Parse: URL parse error: relative URL without a base
First the file where the error occurred is displayed, followed by the number of line and column. The next element displayed is the date and time of the error for the local timezone (to log the date and time Utc::now() is used). To the right of the arrow, the error type will be displayed, and following the colon, the error message. This message comes directly from the crate, it's remapped here but its contents are not modified, meaning that if you got a connection error with, let's say mysql_async, the error message returned from that crate will be redirected to your output.
Using errormapper is very simple. To demonstrate it, we'll use an example of an error connection to a MySQL database, using the mysqlasync crate:
```Rust
async fn example_fn() -> TheResult
let pool = match Pool::from_url(EnvironmentConfig::instance().get_db_url().await) {
Ok(pool) => pool,
Err(e) => {
return Err(map_to_new_error!(e))
}
};
match pool.get_conn().await {
Ok(conn) => Ok(conn),
Err(e) => {
Err(map_to_new_error!(e))
}
}
} ```
The pool variable represents the connection pool returned from trying to contact the database, and will return a
mysql_async::Error error type if it fails.
Since we don't want to deal with this specific error type, we'll use the
map_to_new_error! macro to deal with a generalized and simpler type of error, that actually retains all the original info and adds
some new important and useful data such as the date, time and file location of the error.
The calling function of example_fn() will receive the error as a TheError type, enclosed in a TheResult type. And since
the type TheResult is an alias for the enum core::Result built into Rust, you can propagate the error to control
the execution flow, and handle it elsewhere in case it fails.
The previous example instructions are now contained inside the async function getconn(), then you can call it from our examplefn() and propagate the error if it fails, but continue execution normally if it doesn't:
```Rust
async fn example_fn() -> TheResult
let conn = get_conn().await?;
Ok(conn)
} ```