Add a String.contains function

runtime/interpreter/value.go

@@ -1379,6 +1379,21 @@ func (v *StringValue) GetMember(interpreter *Interpreter, locationRange Location
 			},
 		)
 
+	case sema.StringTypeContainsFunctionName:
+		return NewBoundHostFunctionValue(
+			interpreter,
+			v,
+			sema.StringTypeContainsFunctionType,
+			func(invocation Invocation) Value {
+				other, ok := invocation.Arguments[0].(*StringValue)
+				if !ok {
+					panic(errors.NewUnreachableError())
+				}
+
+				return v.Contains(invocation.Interpreter, other)
+			},
+		)
+
 	case sema.StringTypeDecodeHexFunctionName:
 		return NewBoundHostFunctionValue(
 			interpreter,
@@ -1688,6 +1703,74 @@ func (v *StringValue) ForEach(
 	}
 }
 
+func (v *StringValue) IsBoundaryStart(start int) bool {
+	v.prepareGraphemes()
+	return v.isGraphemeBoundaryStartPrepared(start)
+}
+
+func (v *StringValue) isGraphemeBoundaryStartPrepared(start int) bool {
+
+	for {
+		boundaryStart, _ := v.graphemes.Positions()
+		if start == boundaryStart {
+			return true
+		} else if boundaryStart > start {
+			return false
+		}
+
+		if !v.graphemes.Next() {
+			return false
+		}
+	}
+}
+
+func (v *StringValue) IsBoundaryEnd(end int) bool {
+	v.prepareGraphemes()
+	return v.isGraphemeBoundaryEndPrepared(end)
+}
+
+func (v *StringValue) isGraphemeBoundaryEndPrepared(end int) bool {
+
+	for {
+		_, boundaryEnd := v.graphemes.Positions()
+		if end == boundaryEnd {
+			return true
+		} else if boundaryEnd > end {
+			return false
+		}
+
+		if !v.graphemes.Next() {
+			return false
+		}
+	}
+}
+
+func (v *StringValue) Contains(inter *Interpreter, other *StringValue) BoolValue {
+
+	// Meter computation as if the string was iterated.
+	// This is a conservative over-estimation.
+	inter.ReportComputation(common.ComputationKindLoop, uint(len(v.Str)*len(other.Str)))
+
+	v.prepareGraphemes()
+
+	for start := 0; start < len(v.Str); start++ {
+
+		start = strings.Index(v.Str[start:], other.Str)
+		if start < 0 {
+			break
+		}
+
+		if v.isGraphemeBoundaryStartPrepared(start) &&
+			v.isGraphemeBoundaryEndPrepared(start+len(other.Str)) {
+
+			return TrueValue
+		}
+	}
+
+	return FalseValue
+
+}
+
 type StringValueIterator struct {
 	graphemes *uniseg.Graphemes
 }

runtime/interpreter/value_test.go

@@ -4391,3 +4391,85 @@ func TestValue_ConformsToStaticType(t *testing.T) {
 	})
 
 }
+
+func TestStringIsBoundaryStart(t *testing.T) {
+
+	t.Parallel()
+
+	test := func(s string, i int, expected bool) {
+
+		name := fmt.Sprintf("%s, %d", s, i)
+
+		t.Run(name, func(t *testing.T) {
+			str := NewUnmeteredStringValue(s)
+			assert.Equal(t, expected, str.IsBoundaryStart(i))
+		})
+	}
+
+	test("", 0, true)
+	test("a", 0, true)
+	test("a", 1, false)
+	test("ab", 1, true)
+
+	// 🇪🇸🇪🇪 ("ES", "EE")
+	flagESflagEE := "\U0001F1EA\U0001F1F8\U0001F1EA\U0001F1EA"
+	require.Len(t, flagESflagEE, 16)
+	test(flagESflagEE, 0, true)
+	test(flagESflagEE, 1, false)
+	test(flagESflagEE, 2, false)
+	test(flagESflagEE, 3, false)
+	test(flagESflagEE, 4, false)
+	test(flagESflagEE, 5, false)
+	test(flagESflagEE, 6, false)
+	test(flagESflagEE, 7, false)
+
+	test(flagESflagEE, 8, true)
+	test(flagESflagEE, 9, false)
+	test(flagESflagEE, 10, false)
+	test(flagESflagEE, 11, false)
+	test(flagESflagEE, 12, false)
+	test(flagESflagEE, 13, false)
+	test(flagESflagEE, 14, false)
+	test(flagESflagEE, 15, false)
+}
+
+func TestStringIsBoundaryEnd(t *testing.T) {
+
+	t.Parallel()
+
+	test := func(s string, i int, expected bool) {
+
+		name := fmt.Sprintf("%s, %d", s, i)
+
+		t.Run(name, func(t *testing.T) {
+			str := NewUnmeteredStringValue(s)
+			assert.Equal(t, expected, str.IsBoundaryEnd(i))
+		})
+	}
+
+	test("", 0, true)
+	test("a", 0, true)
+	test("a", 1, true)
+	test("ab", 1, true)
+
+	// 🇪🇸🇪🇪 ("ES", "EE")
+	flagESflagEE := "\U0001F1EA\U0001F1F8\U0001F1EA\U0001F1EA"
+	require.Len(t, flagESflagEE, 16)
+	test(flagESflagEE, 0, true)
+	test(flagESflagEE, 1, false)
+	test(flagESflagEE, 2, false)
+	test(flagESflagEE, 3, false)
+	test(flagESflagEE, 4, false)
+	test(flagESflagEE, 5, false)
+	test(flagESflagEE, 6, false)
+	test(flagESflagEE, 7, false)
+
+	test(flagESflagEE, 8, true)
+	test(flagESflagEE, 9, false)
+	test(flagESflagEE, 10, false)
+	test(flagESflagEE, 11, false)
+	test(flagESflagEE, 12, false)
+	test(flagESflagEE, 13, false)
+	test(flagESflagEE, 14, false)
+	test(flagESflagEE, 15, false)
+}

runtime/sema/string_type.go

@@ -123,6 +123,12 @@ func init() {
 				StringTypeReplaceAllFunctionType,
 				StringTypeReplaceAllFunctionDocString,
 			),
+			NewUnmeteredPublicFunctionMember(
+				t,
+				StringTypeContainsFunctionName,
+				StringTypeContainsFunctionType,
+				stringTypeContainsFunctionDocString,
+			),
 		})
 	}
 }
@@ -170,6 +176,24 @@ It does not modify the original string.
 If either of the parameters are out of the bounds of the string, or the indices are invalid (` + "`from > upTo`" + `), then the function will fail
 `
 
+var StringTypeContainsFunctionType = NewSimpleFunctionType(
+	FunctionPurityView,
+	[]Parameter{
+		{
+			Label:          ArgumentLabelNotRequired,
+			Identifier:     "other",
+			TypeAnnotation: StringTypeAnnotation,
+		},
+	},
+	BoolTypeAnnotation,
+)
+
+const StringTypeContainsFunctionName = "contains"
+
+const stringTypeContainsFunctionDocString = `
+Returns true if this string contains the given other string as a substring.
+`
+
 const StringTypeReplaceAllFunctionName = "replaceAll"
 const StringTypeReplaceAllFunctionDocString = `
 Returns a new string after replacing all the occurrences of parameter ` + "`of` with the parameter `with`" + `.

runtime/tests/checker/string_test.go

@@ -534,3 +534,48 @@ func TestCheckStringReplaceAllTypeMissingArgumentLabelWith(t *testing.T) {
 
 	assert.IsType(t, &sema.MissingArgumentLabelError{}, errs[0])
 }
+
+func TestCheckStringContains(t *testing.T) {
+
+	t.Parallel()
+
+	t.Run("missing argument", func(t *testing.T) {
+
+		t.Parallel()
+
+		_, err := ParseAndCheck(t, `
+		  let a = "abcdef"
+		  let x: Bool = a.contains()
+		`)
+
+		errs := RequireCheckerErrors(t, err, 1)
+
+		assert.IsType(t, &sema.InsufficientArgumentsError{}, errs[0])
+	})
+
+	t.Run("wrong argument type", func(t *testing.T) {
+
+		t.Parallel()
+
+		_, err := ParseAndCheck(t, `
+		  let a = "abcdef"
+		  let x: Bool = a.contains(1)
+		`)
+
+		errs := RequireCheckerErrors(t, err, 1)
+
+		assert.IsType(t, &sema.TypeMismatchError{}, errs[0])
+	})
+
+	t.Run("valid", func(t *testing.T) {
+
+		t.Parallel()
+
+		_, err := ParseAndCheck(t, `
+		  let a = "abcdef"
+		  let x: Bool = a.contains("abc")
+		`)
+
+		require.NoError(t, err)
+	})
+}

runtime/tests/interpreter/interpreter_test.go

@@ -1128,7 +1128,10 @@ func TestInterpretStringSlicing(t *testing.T) {
 	}
 
 	runTest := func(test test) {
-		t.Run("", func(t *testing.T) {
+
+		name := fmt.Sprintf("%s, %d, %d", test.str, test.from, test.to)
+
+		t.Run(name, func(t *testing.T) {
 
 			t.Parallel()
 

runtime/tests/interpreter/string_test.go

@@ -643,3 +643,84 @@ func TestInterpretStringReplaceAll(t *testing.T) {
 	testCase(t, "testEmptyOf", interpreter.NewUnmeteredStringValue("1a1b1c1"))
 	testCase(t, "testNoMatch", interpreter.NewUnmeteredStringValue("pqrS;asdf"))
 }
+
+func TestInterpretStringContains(t *testing.T) {
+
+	t.Parallel()
+
+	type test struct {
+		str    string
+		subStr string
+		result bool
+	}
+
+	tests := []test{
+		{"abcdef", "", true},
+		{"abcdef", "a", true},
+		{"abcdef", "ab", true},
+		{"abcdef", "ac", false},
+		{"abcdef", "b", true},
+		{"abcdef", "bc", true},
+		{"abcdef", "bcd", true},
+		{"abcdef", "c", true},
+		{"abcdef", "cd", true},
+		{"abcdef", "cdef", true},
+		{"abcdef", "cdefg", false},
+		{"abcdef", "abcdef", true},
+		{"abcdef", "abcdefg", false},
+
+		// U+1F476 U+1F3FB is 👶🏻
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", " \\u{1F476}", false},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", "\\u{1F3FB}", false},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", " \\u{1F476}\\u{1F3FB}", true},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", "\\u{1F476}\\u{1F3FB}", true},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", "\\u{1F476}\\u{1F3FB} ", true},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", "\\u{D}", false},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", "\\u{A}", false},
+		{" \\u{1F476}\\u{1F3FB} ascii \\u{D}\\u{A}", " ascii ", true},
+
+		// 🇪🇸🇪🇪 ("ES", "EE") contains 🇪🇸("ES")
+		{"\\u{1F1EA}\\u{1F1F8}\\u{1F1EA}\\u{1F1EA}", "\\u{1F1EA}\\u{1F1F8}", true},
+		// 🇪🇸🇪🇪 ("ES", "EE") contains 🇪🇪 ("EE")
+		{"\\u{1F1EA}\\u{1F1F8}\\u{1F1EA}\\u{1F1EA}", "\\u{1F1EA}\\u{1F1EA}", true},
+		// 🇪🇸🇪🇪 ("ES", "EE") does NOT contain 🇸🇪 ("SE")
+		{"\\u{1F1EA}\\u{1F1F8}\\u{1F1EA}\\u{1F1EA}", "\\u{1F1F8}\\u{1F1EA}", false},
+		// neither prefix nor suffix of codepoints are valid
+		{"\\u{1F1EA}\\u{1F1F8}\\u{1F1EA}\\u{1F1EA}", "\\u{1F1EA}\\u{1F1F8}\\u{1F1EA}", false},
+		{"\\u{1F1EA}\\u{1F1F8}\\u{1F1EA}\\u{1F1EA}", "\\u{1F1F8}\\u{1F1EA}\\u{1F1EA}", false},
+	}
+
+	runTest := func(test test) {
+
+		name := fmt.Sprintf("%s, %s", test.str, test.subStr)
+
+		t.Run(name, func(t *testing.T) {
+
+			t.Parallel()
+
+			inter := parseCheckAndInterpret(t,
+				fmt.Sprintf(
+					`
+                      fun test(): Bool {
+                        let s = "%s"
+                        return s.contains("%s")
+                      }
+                    `,
+					test.str,
+					test.subStr,
+				),
+			)
+
+			value, err := inter.Invoke("test")
+			require.NoError(t, err)
+
+			require.IsType(t, interpreter.BoolValue(true), value)
+			actual := value.(interpreter.BoolValue)
+			require.Equal(t, test.result, bool(actual))
+		})
+	}
+
+	for _, test := range tests {
+		runTest(test)
+	}
+}