#15291: config/interpolate_funcs: Added contains() function to test if a given element is present in the list

config/interpolate_funcs.go

@@ -70,6 +70,7 @@ func Funcs() map[string]ast.Function {
 		"coalescelist": interpolationFuncCoalesceList(),
 		"compact":      interpolationFuncCompact(),
 		"concat":       interpolationFuncConcat(),
+		"contains":     interpolationFuncContains(),
 		"dirname":      interpolationFuncDirname(),
 		"distinct":     interpolationFuncDistinct(),
 		"element":      interpolationFuncElement(),
@@ -356,6 +357,22 @@ func interpolationFuncCoalesceList() ast.Function {
 	}
 }
 
+// interpolationFuncContains returns true if an element is in the list
+// and return false otherwise
+func interpolationFuncContains() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeList, ast.TypeString},
+		ReturnType: ast.TypeBool,
+		Callback: func(args []interface{}) (interface{}, error) {
+			_, err := interpolationFuncIndex().Callback(args)
+			if err != nil {
+				return false, nil
+			}
+			return true, nil
+		},
+	}
+}
+
 // interpolationFuncConcat implements the "concat" function that concatenates
 // multiple lists.
 func interpolationFuncConcat() ast.Function {

config/interpolate_funcs_test.go

@@ -943,6 +943,43 @@ func TestInterpolateFuncConcat(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncContains(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Vars: map[string]ast.Variable{
+			"var.listOfStrings": interfaceToVariableSwallowError([]string{"notfoo", "stillnotfoo", "bar"}),
+			"var.listOfInts":    interfaceToVariableSwallowError([]int{1, 2, 3}),
+		},
+		Cases: []testFunctionCase{
+			{
+				`${contains(var.listOfStrings, "bar")}`,
+				"true",
+				false,
+			},
+
+			{
+				`${contains(var.listOfStrings, "foo")}`,
+				"false",
+				false,
+			},
+			{
+				`${contains(var.listOfInts, 1)}`,
+				"true",
+				false,
+			},
+			{
+				`${contains(var.listOfInts, 10)}`,
+				"false",
+				false,
+			},
+			{
+				`${contains(var.listOfInts, "2")}`,
+				"true",
+				false,
+			},
+		},
+	})
+}
+
 func TestInterpolateFuncMerge(t *testing.T) {
 	testFunction(t, testFunctionConfig{
 		Cases: []testFunctionCase{

website/docs/configuration/interpolation.html.md

@@ -205,6 +205,9 @@ The supported built-in functions are:
   * `concat(list1, list2, ...)` - Combines two or more lists into a single list.
      Example: `concat(aws_instance.db.*.tags.Name, aws_instance.web.*.tags.Name)`
 
+  * `contains(list, element)` - Returns *true* if a list contains the given element
+     and returns *false* otherwise. Examples: `element(var.list_of_strings, "an_element")`
+
   * `dirname(path)` - Returns all but the last element of path, typically the path's directory.
 
   * `distinct(list)` - Removes duplicate items from a list. Keeps the first