Support a config file to use instead of commandline arguments

Signed-off-by: Dave Henderson <[email protected]>

cmd/gomplate/config.go

@@ -0,0 +1,229 @@
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hairyhenderson/gomplate/v3/env"
+	"github.com/hairyhenderson/gomplate/v3/internal/config"
+
+	"github.com/rs/zerolog"
+
+	"github.com/spf13/afero"
+	"github.com/spf13/cobra"
+)
+
+const (
+	defaultConfigFile = ".gomplate.yaml"
+)
+
+var fs = afero.NewOsFs()
+
+// loadConfig is intended to be called before command execution. It:
+// - creates a config.Config from the cobra flags
+// - creates a config.Config from the config file (if present)
+// - merges the two (flags take precedence)
+// - validates the final config
+// - converts the config to a *gomplate.Config for further use (TODO: eliminate this part)
+func loadConfig(cmd *cobra.Command, args []string) (*config.Config, error) {
+	flagConfig, err := cobraConfig(cmd, args)
+	if err != nil {
+		return nil, err
+	}
+
+	cfg, err := readConfigFile(cmd)
+	if err != nil {
+		return nil, err
+	}
+	if cfg == nil {
+		cfg = flagConfig
+	} else {
+		cfg = cfg.MergeFrom(flagConfig)
+	}
+
+	// reset defaults before validation
+	cfg.ApplyDefaults()
+
+	err = cfg.Validate()
+	if err != nil {
+		return nil, fmt.Errorf("failed to validate merged config: %w\n%+v", err, cfg)
+	}
+	return cfg, nil
+}
+
+func pickConfigFile(cmd *cobra.Command) (cfgFile string, required bool) {
+	cfgFile = defaultConfigFile
+	if c := env.Getenv("GOMPLATE_CONFIG"); c != "" {
+		cfgFile = c
+		required = true
+	}
+	if cmd.Flags().Changed("config") && cmd.Flag("config").Value.String() != "" {
+		// Use config file from the flag if specified
+		cfgFile = cmd.Flag("config").Value.String()
+		required = true
+	}
+	return cfgFile, required
+}
+
+func readConfigFile(cmd *cobra.Command) (cfg *config.Config, err error) {
+	ctx := cmd.Context()
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	log := zerolog.Ctx(ctx)
+
+	cfgFile, configRequired := pickConfigFile(cmd)
+
+	f, err := fs.Open(cfgFile)
+	if err != nil {
+		if configRequired {
+			return cfg, fmt.Errorf("config file requested, but couldn't be opened: %w", err)
+		}
+		return nil, nil
+	}
+
+	cfg, err = config.Parse(f)
+	if err != nil && configRequired {
+		return cfg, fmt.Errorf("config file requested, but couldn't be parsed: %w", err)
+	}
+
+	log.Debug().Str("cfgFile", cfgFile).Msg("using config file")
+
+	return cfg, err
+}
+
+// cobraConfig - initialize a config from the commandline options
+func cobraConfig(cmd *cobra.Command, args []string) (cfg *config.Config, err error) {
+	cfg = &config.Config{}
+	cfg.InputFiles, err = getStringSlice(cmd, "file")
+	if err != nil {
+		return nil, err
+	}
+	cfg.Input, err = getString(cmd, "in")
+	if err != nil {
+		return nil, err
+	}
+	cfg.InputDir, err = getString(cmd, "input-dir")
+	if err != nil {
+		return nil, err
+	}
+
+	cfg.ExcludeGlob, err = getStringSlice(cmd, "exclude")
+	if err != nil {
+		return nil, err
+	}
+	includesFlag, err := getStringSlice(cmd, "include")
+	if err != nil {
+		return nil, err
+	}
+	// support --include
+	cfg.ExcludeGlob = processIncludes(includesFlag, cfg.ExcludeGlob)
+
+	cfg.OutputFiles, err = getStringSlice(cmd, "out")
+	if err != nil {
+		return nil, err
+	}
+	cfg.Templates, err = getStringSlice(cmd, "template")
+	if err != nil {
+		return nil, err
+	}
+	cfg.OutputDir, err = getString(cmd, "output-dir")
+	if err != nil {
+		return nil, err
+	}
+	cfg.OutputMap, err = getString(cmd, "output-map")
+	if err != nil {
+		return nil, err
+	}
+	cfg.OutMode, err = getString(cmd, "chmod")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(args) > 0 {
+		cfg.PostExec = args
+	}
+
+	cfg.ExecPipe, err = getBool(cmd, "exec-pipe")
+	if err != nil {
+		return nil, err
+	}
+
+	cfg.LDelim, err = getString(cmd, "left-delim")
+	if err != nil {
+		return nil, err
+	}
+	cfg.RDelim, err = getString(cmd, "right-delim")
+	if err != nil {
+		return nil, err
+	}
+
+	ds, err := getStringSlice(cmd, "datasource")
+	if err != nil {
+		return nil, err
+	}
+	cx, err := getStringSlice(cmd, "context")
+	if err != nil {
+		return nil, err
+	}
+	hdr, err := getStringSlice(cmd, "datasource-header")
+	if err != nil {
+		return nil, err
+	}
+	err = cfg.ParseDataSourceFlags(ds, cx, hdr)
+	if err != nil {
+		return nil, err
+	}
+
+	pl, err := getStringSlice(cmd, "plugin")
+	if err != nil {
+		return nil, err
+	}
+	err = cfg.ParsePluginFlags(pl)
+	if err != nil {
+		return nil, err
+	}
+	return cfg, nil
+}
+
+func getStringSlice(cmd *cobra.Command, flag string) (s []string, err error) {
+	if cmd.Flag(flag) != nil && cmd.Flag(flag).Changed {
+		s, err = cmd.Flags().GetStringSlice(flag)
+	}
+	return s, err
+}
+
+func getString(cmd *cobra.Command, flag string) (s string, err error) {
+	if cmd.Flag(flag) != nil && cmd.Flag(flag).Changed {
+		s, err = cmd.Flags().GetString(flag)
+	}
+	return s, err
+}
+
+func getBool(cmd *cobra.Command, flag string) (b bool, err error) {
+	if cmd.Flag(flag) != nil && cmd.Flag(flag).Changed {
+		b, err = cmd.Flags().GetBool(flag)
+	}
+	return b, err
+}
+
+// process --include flags - these are analogous to specifying --exclude '*',
+// then the inverse of the --include options.
+func processIncludes(includes, excludes []string) []string {
+	if len(includes) == 0 && len(excludes) == 0 {
+		return nil
+	}
+
+	out := []string{}
+	// if any --includes are set, we start by excluding everything
+	if len(includes) > 0 {
+		out = make([]string, 1+len(includes))
+		out[0] = "*"
+	}
+	for i, include := range includes {
+		// includes are just the opposite of an exclude
+		out[i+1] = "!" + include
+	}
+	out = append(out, excludes...)
+	return out
+}