added support for mandatory variables to cli/compose

Signed-off-by: Arash Deshmeh <adeshmeh@ca.ibm.com>

cli/compose/template/template.go

@@ -7,7 +7,7 @@ import (
 )
 
 var delimiter = "\\$"
-var substitution = "[_a-z][_a-z0-9]*(?::?-[^}]+)?"
+var substitution = "[_a-z][_a-z0-9]*(?::?[-?][^}]+)?"
 
 var patternString = fmt.Sprintf(
 	"%s(?i:(?P<escaped>%s)|(?P<named>%s)|{(?P<braced>%s)}|(?P<invalid>))",
@@ -69,6 +69,26 @@ func Substitute(template string, mapping Mapping) (string, error) {
 				return value
 			}
 
+			if strings.Contains(substitution, ":?") {
+				name, errorMessage := partition(substitution, ":?")
+				value, ok := mapping(name)
+				if !ok || value == "" {
+					err = &InvalidTemplateError{Template: errorMessage}
+					return ""
+				}
+				return value
+			}
+
+			if strings.Contains(substitution, "?") {
+				name, errorMessage := partition(substitution, "?")
+				value, ok := mapping(name)
+				if !ok {
+					err = &InvalidTemplateError{Template: errorMessage}
+					return ""
+				}
+				return value
+			}
+
 			// No default (fall back to empty string)
 			value, ok := mapping(substitution)
 			if !ok {

cli/compose/template/template_test.go

@@ -81,3 +81,63 @@ func TestNonAlphanumericDefault(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, "ok /non:-alphanumeric", result)
 }
+
+func TestMandatoryVariableErrors(t *testing.T) {
+	testCases := []struct {
+		template      string
+		expectedError string
+	}{
+		{
+			template:      "not ok ${UNSET_VAR:?Mandatory Variable Unset}",
+			expectedError: "Mandatory Variable Unset",
+		},
+		{
+			template:      "not ok ${BAR:?Mandatory Variable Empty}",
+			expectedError: "Mandatory Variable Empty",
+		},
+		{
+			template:      "not ok ${UNSET_VAR:?}",
+			expectedError: "",
+		},
+		{
+			template:      "not ok ${UNSET_VAR?Mandatory Variable Unset",
+			expectedError: "Mandatory Variable Unset",
+		},
+		{
+			template:      "not ok ${UNSET_VAR?}",
+			expectedError: "",
+		},
+	}
+
+	for _, tc := range testCases {
+		_, err := Substitute(tc.template, defaultMapping)
+		assert.Error(t, err)
+		assert.IsType(t, &InvalidTemplateError{tc.expectedError}, err)
+	}
+}
+
+func TestDefaultsForMandatoryVariables(t *testing.T) {
+	testCases := []struct {
+		template string
+		expected string
+	}{
+		{
+			template: "ok ${FOO:?err}",
+			expected: "ok first",
+		},
+		{
+			template: "ok ${FOO?err}",
+			expected: "ok first",
+		},
+		{
+			template: "ok ${BAR?err}",
+			expected: "ok ",
+		},
+	}
+
+	for _, tc := range testCases {
+		result, err := Substitute(tc.template, defaultMapping)
+		assert.Nil(t, err)
+		assert.Equal(t, tc.expected, result)
+	}
+}