Function interpret

pub fn interpret(err: &Error) -> Option<String>

Interpret an rusqlite::Error into a String.

use rusqlite::Connection;
use sqlite_err_parser::{register_interpreter, InterpretedError, interpret};

fn stringify(ie: &InterpretedError) -> Option<String> {
  match ie {
    InterpretedError::NotUnique(ids) => match ids.as_slice() {
      [("testtbl1", "id")] => Some("id already exists".into()),
      [("testtbl1", "name")] => Some("name already exists".into()),
      [("testtbl2", "name1"), ("testtbl2", "name2")] => {
        Some("name pair already exists".into())
      }
      _ => None
    },
    InterpretedError::Check(rule) => None,
    _ => None
  }
}

// Register translator function.
register_interpreter(stringify);

// Open and initialize database
let conn = Connection::open_in_memory().unwrap();
conn
   .execute("CREATE TABLE IF NOT EXISTS testtbl1 (
  id   INTEGER PRIMARY KEY,
  name TEXT UNIQUE NOT NULL
);", []).unwrap();
 conn
   .execute("CREATE TABLE IF NOT EXISTS testtbl2 (
  id    INTEGER PRIMARY KEY,
  name1 TEXT NOT NULL,
  name2 TEXT NOT NULL,
  UNIQUE(name1, name2)
);", []).unwrap();

// Populate with some test data
conn.execute(
  "INSERT INTO testtbl1 (id, name) VALUES (1, 'frank');", []
).unwrap();
conn.execute(
  "INSERT INTO testtbl2 (id, name1, name2) VALUES (1, 'bill', 'frank');",
  []
).unwrap();

// testtbl1.id uniqueness violation
let err = conn.execute(
  "INSERT INTO testtbl1 (id, name) VALUES (1, 'bill');", []
).unwrap_err();
assert_eq!(interpret(&err), Some("id already exists".into()));

// testtbl1.name uniqueness violation
let err = conn.execute(
  "INSERT INTO testtbl1 (name) VALUES ('frank');", []
).unwrap_err();
assert_eq!(interpret(&err), Some("name already exists".into()));

// (testtbl2.name1, testtbl2.name2) uniqueness violation
let err = conn.execute(
  "INSERT INTO testtbl2 (name1, name2) VALUES ('bill', 'frank');", []
).unwrap_err();
assert_eq!(interpret(&err), Some("name pair already exists".into()));