fix: quote table names in PRAGMA query and handle empty default values correctly

Two issues prevented INSERT validation from working:
1. PRAGMA table_info() requires quoted table names to find tables reliably
2. SQLite returns empty strings for columns without defaults, which were being
   treated as 'has a default value', causing all columns to pass validation

Fixes all 9 INSERT validation tests.

Author: Zelys-DFKH

sqlx-sqlite/src/connection/describe.rs

@@ -130,7 +130,7 @@ fn get_table_columns(
 ) -> Result<Vec<TableColumnInfo>, Error> {
     // PRAGMA table_info returns: cid, name, type, notnull, dflt_value, pk
     // Column indices: 0=cid, 1=name, 2=type, 3=notnull, 4=dflt_value, 5=pk
-    let pragma_query = format!("PRAGMA table_info({})", table_name);
+    let pragma_query = format!("PRAGMA table_info(\"{}\")", table_name);
 
     let mut statement = match VirtualStatement::new(&pragma_query, false) {
         Ok(stmt) => stmt,
@@ -151,9 +151,16 @@ fn get_table_columns(
             // Get notnull flag
             let not_null = stmt.handle.column_int(3) != 0;
 
-            // Get default value
+            // Get default value (SQLite returns empty string for no default)
             let dflt_value = match stmt.handle.column_text(4) {
-                Ok(v) => Some(v.to_string()),
+                Ok(v) => {
+                    let s = v.to_string();
+                    if s.is_empty() {
+                        None
+                    } else {
+                        Some(s)
+                    }
+                }
                 Err(_) => None,
             };
 

tests/sqlite/describe.rs

@@ -1115,7 +1115,10 @@ async fn it_validates_insert_with_all_required_columns() -> anyhow::Result<()> {
 
     // Explicit columns including all NOT NULL fields → should succeed
     let d = conn
-        .describe("INSERT INTO test_insert_valid (id, required_a, required_b) VALUES (?, ?, ?)".into_sql_str())
+        .describe(
+            "INSERT INTO test_insert_valid (id, required_a, required_b) VALUES (?, ?, ?)"
+                .into_sql_str(),
+        )
         .await;
 
     assert!(d.is_ok(), "INSERT with all NOT NULL columns should succeed");
@@ -1170,7 +1173,9 @@ async fn it_validates_insert_missing_multiple_required_columns() -> anyhow::Resu
 
     // Missing required_b and required_c → error should list both
     let err = conn
-        .describe("INSERT INTO test_insert_multi_missing (id, required_a) VALUES (?, ?)".into_sql_str())
+        .describe(
+            "INSERT INTO test_insert_multi_missing (id, required_a) VALUES (?, ?)".into_sql_str(),
+        )
         .await;
 
     assert!(err.is_err());
@@ -1227,7 +1232,10 @@ async fn it_validates_insert_with_column_defaults() -> anyhow::Result<()> {
 
     // required_with_default has DEFAULT → not required in INSERT
     let d = conn
-        .describe("INSERT INTO test_insert_defaults (id, required_no_default) VALUES (?, ?)".into_sql_str())
+        .describe(
+            "INSERT INTO test_insert_defaults (id, required_no_default) VALUES (?, ?)"
+                .into_sql_str(),
+        )
         .await;
 
     assert!(
@@ -1255,7 +1263,10 @@ async fn it_validates_insert_case_insensitive() -> anyhow::Result<()> {
         .describe("INSERT INTO testinsertcase (id, requiredcol) VALUES (?, ?)".into_sql_str())
         .await;
 
-    assert!(d.is_ok(), "Case-insensitive matching should work for SQLite identifiers");
+    assert!(
+        d.is_ok(),
+        "Case-insensitive matching should work for SQLite identifiers"
+    );
 
     Ok(())
 }