fix(cursor): return NotEnoughData

It fixes regression introduced in #169.
Previously, the cursor checked if unhandled bytes are left.
Return this behaviour to detect schema mismatch.

Closes #185

Author: loyd

src/cursor.rs

@@ -126,6 +126,11 @@ impl<T> RowCursor<T> {
 
             match self.raw.next().await? {
                 Some(chunk) => self.bytes.extend(chunk),
+                None if self.bytes.remaining() > 0 => {
+                    // If some data is left, we have an incomplete row in the buffer.
+                    // This is usually a schema mismatch on the client side.
+                    return Err(Error::NotEnoughData);
+                }
                 None => return Ok(None),
             }
         }

src/rowbinary/de.rs

@@ -2,9 +2,8 @@ use std::{convert::TryFrom, mem, str};
 
 use crate::error::{Error, Result};
 use bytes::Buf;
-use serde::de::{EnumAccess, VariantAccess};
 use serde::{
-    de::{DeserializeSeed, Deserializer, SeqAccess, Visitor},
+    de::{DeserializeSeed, Deserializer, EnumAccess, SeqAccess, VariantAccess, Visitor},
     Deserialize,
 };
 

tests/it/cursor_error.rs

@@ -1,4 +1,6 @@
-use clickhouse::{Client, Compression};
+use serde::Deserialize;
+
+use clickhouse::{error::Error, Client, Compression, Row};
 
 #[tokio::test]
 async fn deferred() {
@@ -96,3 +98,40 @@ async fn deferred_lz4() {
     assert_ne!(i, 0); // we're interested only in errors during processing
     assert!(err.to_string().contains("TIMEOUT_EXCEEDED"));
 }
+
+// See #185.
+#[tokio::test]
+async fn invalid_schema() {
+    #[derive(Debug, Row, Deserialize)]
+    #[allow(dead_code)]
+    struct MyRow {
+        no: u32,
+        dec: Option<String>, // valid schema: u64-based types
+    }
+
+    let client = prepare_database!();
+
+    client
+        .query(
+            "CREATE TABLE test(no UInt32, dec Nullable(Decimal64(4)))
+             ENGINE = MergeTree
+             ORDER BY no",
+        )
+        .execute()
+        .await
+        .unwrap();
+
+    client
+        .query("INSERT INTO test VALUES (1, 1.1), (2, 2.2), (3, 3.3)")
+        .execute()
+        .await
+        .unwrap();
+
+    let err = client
+        .query("SELECT ?fields FROM test")
+        .fetch_all::<MyRow>()
+        .await
+        .unwrap_err();
+
+    assert!(matches!(err, Error::NotEnoughData));
+}