py: handle corner cases for str.find

Signed-off-by: Sebastien Binet <binet@cern.ch>

Author: sbinet

py/string.go

@@ -602,11 +602,18 @@ func (s String) find(args Tuple) (Object, error) {
 	}
 
 	var (
-		beg = int(pybeg.(Int))
-		end = int(pyend.(Int))
+		beg  = int(pybeg.(Int))
+		end  = int(pyend.(Int))
+		size = s.len()
 	)
+	if beg > size {
+		beg = size
+	}
 	if end < 0 {
-		end = s.len()
+		end = size
+	}
+	if end > size {
+		end = size
 	}
 
 	var (

py/string_test.go

@@ -67,6 +67,20 @@ func TestStringFind(t *testing.T) {
 			end: -1,
 			idx: 6,
 		},
+		{
+			str: "0123456789",
+			sub: "6",
+			beg: 100,
+			end: -1,
+			idx: -1,
+		},
+		{
+			str: "0123456789",
+			sub: "6",
+			beg: 2,
+			end: 1,
+			idx: -1,
+		},
 	} {
 		t.Run(tc.str+":"+tc.sub, func(t *testing.T) {
 			beg := tc.beg