Add the trim() interpolation function

config/interpolate_funcs.go

@@ -41,6 +41,7 @@ func Funcs() map[string]ast.Function {
 		"split":        interpolationFuncSplit(),
 		"sha1":         interpolationFuncSha1(),
 		"sha256":       interpolationFuncSha256(),
+		"strip":        interpolationFuncStrip(),
 		"base64encode": interpolationFuncBase64Encode(),
 		"base64decode": interpolationFuncBase64Decode(),
 		"upper":        interpolationFuncUpper(),
@@ -617,3 +618,14 @@ func interpolationFuncSha256() ast.Function {
 		},
 	}
 }
+
+func interpolationFuncTrim() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			trim := args[0].(string)
+			return strings.TrimSpace(trim), nil
+		},
+	}
+}

config/interpolate_funcs_test.go

@@ -858,6 +858,18 @@ func TestInterpolateFuncSha256(t *testing.T) {
 	})
 }
 
+func TestInterpolateFuncTrim(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${trim(" test ")}`,
+				"test",
+				false,
+			},
+		},
+	})
+}
+
 type testFunctionConfig struct {
 	Cases []testFunctionCase
 	Vars  map[string]ast.Variable

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

@@ -176,6 +176,8 @@ The supported built-in functions are:
       `a_resource_param = ["${split(",", var.CSV_STRING)}"]`.
       Example: `split(",", module.amod.server_ids)`
 
+  * `trim(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.
 
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