Change to_namespaced_keyword(s) to return a Result rather than Option to (#333)

reduce error handling throughout db code. Fixes #331. r=nalexander

db/src/db.rs

@@ -346,8 +346,6 @@ impl TypedSQLValue for TypedValue {
             (10, rusqlite::types::Value::Text(x)) => Ok(TypedValue::String(x)),
             (13, rusqlite::types::Value::Text(x)) => {
                 to_namespaced_keyword(&x).map(|k| TypedValue::Keyword(k))
-                    // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
-                    .ok_or(ErrorKind::NotYetImplemented(format!("InvalidNamespacedKeyword: {}", x)).into())
             },
             (_, value) => bail!(ErrorKind::BadSQLValuePair(value, value_type_tag)),
         }
@@ -402,10 +400,7 @@ pub fn read_ident_map(conn: &rusqlite::Connection) -> Result<IdentMap> {
     let mut stmt: rusqlite::Statement = conn.prepare("SELECT ident, entid FROM idents")?;
     let m = stmt.query_and_then(&[], |row| -> Result<(symbols::NamespacedKeyword, Entid)> {
         let ident: String = row.get(0);
-        to_namespaced_keyword(&ident)
+        to_namespaced_keyword(&ident).map(|i| (i, row.get(1)))
-            .map(|i| (i, row.get(1)))
-            // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
-            .ok_or(ErrorKind::NotYetImplemented(format!("InvalidNamespacedKeyword: {}", ident.clone())).into())
     })?.collect();
     m
 }
@@ -435,13 +430,9 @@ pub fn read_schema(conn: &rusqlite::Connection, ident_map: &IdentMap) -> Result<
         let ident = to_namespaced_keyword(&symbolic_ident);
         let attr = to_namespaced_keyword(&symbolic_attr);
         match (ident, attr, typed_value) {
-            (Some(ident), Some(attr), typed_value) => Ok((ident, attr, typed_value)),
+            (Ok(ident), Ok(attr), typed_value) => Ok((ident, attr, typed_value)),
-            (None, _, _) =>
+            (Err(e), _, _) => Err(e),
-                // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
+            (_, Err(e), _) => Err(e),
-                Err(ErrorKind::NotYetImplemented(format!("InvalidNamespacedKeyword: {}", &symbolic_ident)).into()),
-            (_, None, _) =>
-                // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
-                Err(ErrorKind::NotYetImplemented(format!("InvalidNamespacedKeyword: {}", &symbolic_attr)).into()),
         }
     })?.collect();
 

db/src/lib.rs

@@ -26,6 +26,7 @@ extern crate mentat_tx_parser;
 
 use itertools::Itertools;
 use std::iter::repeat;
+use errors::{ErrorKind, Result};
 
 pub mod db;
 mod bootstrap;
@@ -46,13 +47,16 @@ use edn::symbols;
 // TODO: replace with sqlite3_limit. #288.
 pub const SQLITE_MAX_VARIABLE_NUMBER: usize = 999;
 
-pub fn to_namespaced_keyword(s: &str) -> Option<symbols::NamespacedKeyword> {
+pub fn to_namespaced_keyword(s: &str) -> Result<symbols::NamespacedKeyword> {
     let splits = [':', '/'];
     let mut i = s.split(&splits[..]);
-    match (i.next(), i.next(), i.next(), i.next()) {
+    let nsk = match (i.next(), i.next(), i.next(), i.next()) {
         (Some(""), Some(namespace), Some(name), None) => Some(symbols::NamespacedKeyword::new(namespace, name)),
-        _ => None
+        _ => None,
-    }
+    };
+
+    // TODO Use custom ErrorKind https://github.com/brson/error-chain/issues/117
+    nsk.ok_or(ErrorKind::NotYetImplemented(format!("InvalidNamespacedKeyword: {}", s)).into())
 }
 
 /// Prepare an SQL `VALUES` block, like (?, ?, ?), (?, ?, ?).

db/src/schema.rs

@@ -11,7 +11,7 @@
 #![allow(dead_code)]
 
 use entids;
-use errors::*;
+use errors::{ErrorKind, Result};
 use edn::symbols;
 use mentat_core::{
     Attribute,