Merge 'substr scalar should also work with non-text values' from Diego Reis

Closes #3306
Not only blobs, but numbers are also cast to text

Closes #3439

core/types.rs

@@ -387,6 +387,7 @@ impl Value {
         };
     }
 
+    /// Cast Value to String, if Value is NULL returns None
     pub fn cast_text(&self) -> Option<String> {
         Some(match self {
             Value::Null => return None,

core/vdbe/execute.rs

@@ -8352,12 +8352,12 @@ impl Value {
     }
 
     pub fn exec_substring(
-        str_value: &Value,
+        value: &Value,
         start_value: &Value,
         length_value: Option<&Value>,
     ) -> Value {
-        if let (Value::Text(str), Value::Integer(start)) = (str_value, start_value) {
-            let str_len = str.as_str().len() as i64;
+        if let (Some(str), Value::Integer(start)) = (value.cast_text(), start_value) {
+            let str_len = str.len() as i64;
 
             // The left-most character of X is number 1.
             // If Y is negative then the first character of the substring is found by counting from the right rather than the left.

testing/scalar-functions.test

@@ -622,6 +622,27 @@ do_execsql_test substring-2-args-exceed-length {
   SELECT substring('limbo', 10);
 } {}
 
+do_execsql_test substring-with-blob {
+    select substr(x'446F6E7450616E696321', 0);
+} {DontPanic!}
+
+do_execsql_test substring-with-blob-size {
+    select substr(x'446F6E7450616E696321', 5, 6);
+} {Panic!}
+
+# https://github.com/tursodatabase/turso/issues/3306
+do_execsql_test substring-with-blob-sanity {
+    with t as (select hex(substr(x'414243',2,1)) as slice) select slice, typeof(slice), length(slice) from t;
+} {42|text|2}
+
+do_execsql_test substring-with-numbers {
+    select substr(12345678987654, 5, 6);
+} {567898}
+
+do_execsql_test substring-with-numbers {
+    select substr(12345678987654, 0);
+} {12345678987654}
+
 do_execsql_test typeof-null {
   SELECT typeof(null);
 } {null}