Better error reporting on invalid column type.

src/types/chrono.rs

@@ -21,8 +21,8 @@ impl ToSql for NaiveDate {
 
 /// "YYYY-MM-DD" => ISO 8601 calendar date without timezone.
 impl FromSql for NaiveDate {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_str().and_then(|s| match NaiveDate::parse_from_str(s, "%Y-%m-%d") {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_str(idx).and_then(|s| match NaiveDate::parse_from_str(s, "%Y-%m-%d") {
             Ok(dt) => Ok(dt),
             Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
         })
@@ -39,8 +39,8 @@ impl ToSql for NaiveTime {
 
 /// "HH:MM"/"HH:MM:SS"/"HH:MM:SS.SSS" => ISO 8601 time without timezone.
 impl FromSql for NaiveTime {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_str().and_then(|s| {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_str(idx).and_then(|s| {
             let fmt = match s.len() {
                 5 => "%H:%M",
                 8 => "%H:%M:%S",
@@ -65,8 +65,8 @@ impl ToSql for NaiveDateTime {
 /// "YYYY-MM-DD HH:MM:SS"/"YYYY-MM-DD HH:MM:SS.SSS" => ISO 8601 combined date and time
 /// without timezone. ("YYYY-MM-DDTHH:MM:SS"/"YYYY-MM-DDTHH:MM:SS.SSS" also supported)
 impl FromSql for NaiveDateTime {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_str().and_then(|s| {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_str(idx).and_then(|s| {
             let fmt = if s.len() >= 11 && s.as_bytes()[10] == b'T' {
                 "%Y-%m-%dT%H:%M:%S%.f"
             } else {
@@ -91,10 +91,10 @@ impl<Tz: TimeZone> ToSql for DateTime<Tz> {
 
 /// RFC3339 ("YYYY-MM-DDTHH:MM:SS.SSS[+-]HH:MM") into DateTime<UTC>.
 impl FromSql for DateTime<UTC> {
-    fn column_result(value: ValueRef) -> Result<Self> {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
         {
             // Try to parse value as rfc3339 first.
-            let s = try!(value.as_str());
+            let s = try!(value.as_str(idx));
 
             // If timestamp looks space-separated, make a copy and replace it with 'T'.
             let s = if s.len() >= 11 && s.as_bytes()[10] == b' ' {
@@ -115,14 +115,14 @@ impl FromSql for DateTime<UTC> {
         }
 
         // Couldn't parse as rfc3339 - fall back to NaiveDateTime.
-        NaiveDateTime::column_result(value).map(|dt| UTC.from_utc_datetime(&dt))
+        NaiveDateTime::column_result(value, idx).map(|dt| UTC.from_utc_datetime(&dt))
     }
 }
 
 /// RFC3339 ("YYYY-MM-DDTHH:MM:SS.SSS[+-]HH:MM") into DateTime<Local>.
 impl FromSql for DateTime<Local> {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        let utc_dt = try!(DateTime::<UTC>::column_result(value));
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        let utc_dt = try!(DateTime::<UTC>::column_result(value, idx));
         Ok(utc_dt.with_timezone(&Local))
     }
 }

src/types/from_sql.rs

@@ -4,34 +4,34 @@ use ::error::Error;
 
 /// A trait for types that can be created from a SQLite value.
 pub trait FromSql: Sized {
-    fn column_result(value: ValueRef) -> Result<Self>;
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self>;
 }
 
 impl FromSql for i32 {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        i64::column_result(value).map(|i| i as i32)
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        i64::column_result(value, idx).map(|i| i as i32)
     }
 }
 
 impl FromSql for i64 {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_i64()
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_i64(idx)
     }
 }
 
 impl FromSql for f64 {
-    fn column_result(value: ValueRef) -> Result<Self> {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
         match value {
             ValueRef::Integer(i) => Ok(i as f64),
             ValueRef::Real(f) => Ok(f),
-            _ => Err(Error::InvalidColumnType),
+            _ => Err(Error::InvalidColumnType(idx, value.data_type())),
         }
     }
 }
 
 impl FromSql for bool {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        i64::column_result(value).map(|i| match i {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        i64::column_result(value, idx).map(|i| match i {
             0 => false,
             _ => true,
         })
@@ -39,28 +39,28 @@ impl FromSql for bool {
 }
 
 impl FromSql for String {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_str().map(|s| s.to_string())
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_str(idx).map(|s| s.to_string())
     }
 }
 
 impl FromSql for Vec<u8> {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_blob().map(|b| b.to_vec())
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_blob(idx).map(|b| b.to_vec())
     }
 }
 
 impl<T: FromSql> FromSql for Option<T> {
-    fn column_result(value: ValueRef) -> Result<Self> {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
         match value {
             ValueRef::Null => Ok(None),
-            _ => FromSql::column_result(value).map(Some),
+            _ => FromSql::column_result(value, idx).map(Some),
         }
     }
 }
 
 impl FromSql for Value {
-    fn column_result(value: ValueRef) -> Result<Self> {
+    fn column_result(value: ValueRef, _: i32) -> Result<Self> {
         Ok(value.into())
     }
 }

src/types/mod.rs

@@ -56,6 +56,8 @@ pub use self::from_sql::FromSql;
 pub use self::to_sql::ToSql;
 pub use self::value_ref::ValueRef;
 
+use std::fmt;
+
 mod value_ref;
 mod from_sql;
 mod to_sql;
@@ -102,6 +104,39 @@ pub enum Value {
     Blob(Vec<u8>),
 }
 
+impl Value {
+    pub fn data_type(&self) -> Type {
+        match *self {
+            Value::Null => Type::Null,
+            Value::Integer(_) => Type::Integer,
+            Value::Real(_) => Type::Real,
+            Value::Text(_) => Type::Text,
+            Value::Blob(_) => Type::Blob,
+        }
+    }
+}
+
+#[derive(Clone,Debug,PartialEq)]
+pub enum Type {
+    Null,
+    Integer,
+    Real,
+    Text,
+    Blob,
+}
+
+impl fmt::Display for Type {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Type::Null => write!(f, "Null"),
+            Type::Integer => write!(f, "Integer"),
+            Type::Real => write!(f, "Real"),
+            Type::Text => write!(f, "Text"),
+            Type::Blob => write!(f, "Blob"),
+        }
+    }
+}
+
 #[cfg(test)]
 #[cfg_attr(feature="clippy", allow(similar_names))]
 mod test {
@@ -175,7 +210,7 @@ mod test {
     fn test_mismatched_types() {
         fn is_invalid_column_type(err: Error) -> bool {
             match err {
-                Error::InvalidColumnType => true,
+                Error::InvalidColumnType(_, _) => true,
                 _ => false,
             }
         }

src/types/serde_json.rs

@@ -19,12 +19,13 @@ impl ToSql for Value {
 
 /// Deserialize text/blob to JSON `Value`.
 impl FromSql for Value {
-    fn column_result(value: ValueRef) -> Result<Self> {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
         match value {
-            ValueRef::Text(ref s) => serde_json::from_str(s),
-            ValueRef::Blob(ref b) => serde_json::from_slice(b),
-            _ => return Err(Error::InvalidColumnType),
-        }.map_err(|err| Error::FromSqlConversionFailure(Box::new(err)))
+                ValueRef::Text(ref s) => serde_json::from_str(s),
+                ValueRef::Blob(ref b) => serde_json::from_slice(b),
+                _ => return Err(Error::InvalidColumnType(idx, value.data_type())),
+            }
+            .map_err(|err| Error::FromSqlConversionFailure(Box::new(err)))
     }
 }
 

src/types/time.rs

@@ -16,8 +16,8 @@ impl ToSql for time::Timespec {
 }
 
 impl FromSql for time::Timespec {
-    fn column_result(value: ValueRef) -> Result<Self> {
-        value.as_str().and_then(|s| match time::strptime(s, SQLITE_DATETIME_FMT) {
+    fn column_result(value: ValueRef, idx: i32) -> Result<Self> {
+        value.as_str(idx).and_then(|s| match time::strptime(s, SQLITE_DATETIME_FMT) {
             Ok(tm) => Ok(tm.to_timespec()),
             Err(err) => Err(Error::FromSqlConversionFailure(Box::new(err))),
         })

src/types/value_ref.rs

@@ -1,6 +1,6 @@
 use ::Result;
 use ::error::Error;
-use super::Value;
+use super::{Value, Type};
 
 /// A non-owning [dynamic type value](http://sqlite.org/datatype3.html). Typically the
 /// memory backing this value is owned by SQLite.
@@ -20,40 +20,52 @@ pub enum ValueRef<'a> {
     Blob(&'a [u8]),
 }
 
+impl<'a> ValueRef<'a> {
+    pub fn data_type(&self) -> Type {
+        match *self {
+            ValueRef::Null => Type::Null,
+            ValueRef::Integer(_) => Type::Integer,
+            ValueRef::Real(_) => Type::Real,
+            ValueRef::Text(_) => Type::Text,
+            ValueRef::Blob(_) => Type::Blob,
+        }
+    }
+}
+
 impl<'a> ValueRef<'a> {
     /// If `self` is case `Integer`, returns the integral value. Otherwise, returns
     /// `Err(Error::InvalidColumnType)`.
-    pub fn as_i64(&self) -> Result<i64> {
+    pub fn as_i64(&self, idx: i32) -> Result<i64> {
         match *self {
             ValueRef::Integer(i) => Ok(i),
-            _ => Err(Error::InvalidColumnType),
+            _ => Err(Error::InvalidColumnType(idx, self.data_type())),
         }
     }
 
     /// If `self` is case `Real`, returns the floating point value. Otherwise, returns
     /// `Err(Error::InvalidColumnType)`.
-    pub fn as_f64(&self) -> Result<f64> {
+    pub fn as_f64(&self, idx: i32) -> Result<f64> {
         match *self {
             ValueRef::Real(f) => Ok(f),
-            _ => Err(Error::InvalidColumnType),
+            _ => Err(Error::InvalidColumnType(idx, self.data_type())),
         }
     }
 
     /// If `self` is case `Text`, returns the string value. Otherwise, returns
     /// `Err(Error::InvalidColumnType)`.
-    pub fn as_str(&self) -> Result<&str> {
+    pub fn as_str(&self, idx: i32) -> Result<&str> {
         match *self {
             ValueRef::Text(ref t) => Ok(t),
-            _ => Err(Error::InvalidColumnType),
+            _ => Err(Error::InvalidColumnType(idx, self.data_type())),
         }
     }
 
     /// If `self` is case `Blob`, returns the byte slice. Otherwise, returns
     /// `Err(Error::InvalidColumnType)`.
-    pub fn as_blob(&self) -> Result<&[u8]> {
+    pub fn as_blob(&self, idx: i32) -> Result<&[u8]> {
         match *self {
             ValueRef::Blob(ref b) => Ok(b),
-            _ => Err(Error::InvalidColumnType),
+            _ => Err(Error::InvalidColumnType(idx, self.data_type())),
         }
     }
 }