Method shellPreprocessArgs

cmd/dagger/shell_exec.go:504–646

shellPreprocessArgs converts positional arguments to flag arguments Values are not processed. This function is used to leverage pflags to parse flags interspersed with positional arguments, so a function's required arguments can be placed anywhere. Then we get the unprocessed flags in order to vali

(
	ctx context.Context,
	fn *modFunction,
	args []string,
)

// Additionally, if there's only one required argument that is a list of strings,
// all positional arguments are used as elements of that list.
func (h *shellCallHandler) shellPreprocessArgs(
	ctx context.Context,
	fn *modFunction,
	args []string,
) (map[string]any, []string, error) {
	// Final map of resolved argument values
	values := make(map[string]any, len(fn.Args))

	flags := pflag.NewFlagSet(fn.CmdName(), pflag.ContinueOnError)
	flags.SetOutput(io.MultiWriter(
		interp.HandlerCtx(ctx).Stderr,
		telemetry.SpanStdio(ctx, InstrumentationLibrary).Stderr,
	))

	opts := fn.OptionalArgs()
	reqs := fn.RequiredArgs()

	// All CLI arguments are strings at first, but booleans can be omitted.
	// We don't wan't to process values yet, just validate and consume the flags
	// so we get the remaining positional args.

	// Add required arguments as flags so they can be specified as named arguments
	for _, arg := range reqs {
		name := arg.FlagName()

		switch arg.TypeDef.Kind {
		case dagger.TypeDefKindListKind:
			switch arg.TypeDef.AsList.ElementTypeDef.Kind {
			case dagger.TypeDefKindBooleanKind:
				flags.BoolSlice(name, nil, "")
			default:
				flags.StringSlice(name, nil, "")
			}
		case dagger.TypeDefKindBooleanKind:
			flags.Bool(name, false, "")
		default:
			flags.String(name, "", "")
		}
	}

	// Add optional arguments as flags
	for _, arg := range opts {
		name := arg.FlagName()

		switch arg.TypeDef.Kind {
		case dagger.TypeDefKindListKind:
			switch arg.TypeDef.AsList.ElementTypeDef.Kind {
			case dagger.TypeDefKindBooleanKind:
				flags.BoolSlice(name, nil, "")
			default:
				flags.StringSlice(name, nil, "")
			}
		case dagger.TypeDefKindBooleanKind:
			flags.Bool(name, false, "")
		default:
			flags.String(name, "", "")
		}
	}