Adds ‘tittle’ built-in function. (#9087)

The tittle function returns a copy of the string with the first characters of all the words capitalized.

config/interpolate_funcs.go

@@ -81,6 +81,7 @@ func Funcs() map[string]ast.Function {
 		"signum":       interpolationFuncSignum(),
 		"sort":         interpolationFuncSort(),
 		"split":        interpolationFuncSplit(),
+		"title":        interpolationFuncTitle(),
 		"trimspace":    interpolationFuncTrimSpace(),
 		"upper":        interpolationFuncUpper(),
 	}
@@ -996,3 +997,16 @@ func interpolationFuncUUID() ast.Function {
 		},
 	}
 }
+
+// interpolationFuncTitle implements the "title" function that returns a copy of the
+// string in which first characters of all the words are capitalized.
+func interpolationFuncTitle() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			toTitle := args[0].(string)
+			return strings.Title(toTitle), nil
+		},
+	}
+}

config/interpolate_funcs_test.go

@@ -1553,6 +1553,36 @@ func TestInterpolateFuncSha256(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncTitle(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${title("hello")}`,
+				"Hello",
+				false,
+			},
+
+			{
+				`${title("hello world")}`,
+				"Hello World",
+				false,
+			},
+
+			{
+				`${title("")}`,
+				"",
+				false,
+			},
+
+			{
+				`${title()}`,
+				nil,
+				true,
+			},
+		},
+	})
+}
+
 func TestInterpolateFuncTrimSpace(t *testing.T) {
 	testFunction(t, testFunctionConfig{
 		Cases: []testFunctionCase{

website/source/docs/configuration/interpolation.html.md

@@ -240,6 +240,8 @@ The supported built-in functions are:
       `a_resource_param = ["${split(",", var.CSV_STRING)}"]`.
       Example: `split(",", module.amod.server_ids)`
 
+  * `title(string)` - Returns a copy of the string with the first characters of all the words capitalized.
+
   * `trimspace(string)` - Returns a copy of the string with all leading and trailing white spaces removed.
 
   * `upper(string)` - Returns a copy of the string with all Unicode letters mapped to their upper case.