diff --git a/config/interpolate_funcs.go b/config/interpolate_funcs.go index e98ade2f0..5538763c0 100644 --- a/config/interpolate_funcs.go +++ b/config/interpolate_funcs.go @@ -25,6 +25,7 @@ func init() { "cidrhost": interpolationFuncCidrHost(), "cidrnetmask": interpolationFuncCidrNetmask(), "cidrsubnet": interpolationFuncCidrSubnet(), + "coalesce": interpolationFuncCoalesce(), "compact": interpolationFuncCompact(), "concat": interpolationFuncConcat(), "element": interpolationFuncElement(), @@ -145,6 +146,30 @@ func interpolationFuncCidrSubnet() ast.Function { } } +// interpolationFuncCoalesce implements the "coalesce" function that +// returns the first non null / empty string from the provided input +func interpolationFuncCoalesce() ast.Function { + return ast.Function{ + ArgTypes: []ast.Type{ast.TypeString}, + ReturnType: ast.TypeString, + Variadic: true, + VariadicType: ast.TypeString, + Callback: func(args []interface{}) (interface{}, error) { + if len(args) < 2 { + return nil, fmt.Errorf("must provide at least two arguments") + } + for _, arg := range args { + argument := arg.(string) + + if argument != "" { + return argument, nil + } + } + return "", nil + }, + } +} + // interpolationFuncConcat implements the "concat" function that // concatenates multiple strings. This isn't actually necessary anymore // since our language supports string concat natively, but for backwards diff --git a/config/interpolate_funcs_test.go b/config/interpolate_funcs_test.go index bbfdd484a..3aeb50db1 100644 --- a/config/interpolate_funcs_test.go +++ b/config/interpolate_funcs_test.go @@ -147,6 +147,33 @@ func TestInterpolateFuncCidrSubnet(t *testing.T) { }) } +func TestInterpolateFuncCoalesce(t *testing.T) { + testFunction(t, testFunctionConfig{ + Cases: []testFunctionCase{ + { + `${coalesce("first", "second", "third")}`, + "first", + false, + }, + { + `${coalesce("", "second", "third")}`, + "second", + false, + }, + { + `${coalesce("", "", "")}`, + "", + false, + }, + { + `${coalesce("foo")}`, + nil, + true, + }, + }, + }) +} + func TestInterpolateFuncDeprecatedConcat(t *testing.T) { testFunction(t, testFunctionConfig{ Cases: []testFunctionCase{ diff --git a/website/source/docs/configuration/interpolation.html.md b/website/source/docs/configuration/interpolation.html.md index 049c71825..21efbd83e 100644 --- a/website/source/docs/configuration/interpolation.html.md +++ b/website/source/docs/configuration/interpolation.html.md @@ -95,6 +95,9 @@ The supported built-in functions are: CIDR notation (like ``10.0.0.0/8``) and extends its prefix to include an additional subnet number. For example, ``cidrsubnet("10.0.0.0/8", 8, 2)`` returns ``10.2.0.0/16``. + + * `coalesce(string1, string2, ...)` - Returns the first non-empty value from + the given arguments. At least two arguments must be provided. * `compact(list)` - Removes empty string elements from a list. This can be useful in some cases, for example when passing joined lists as module