Create limactl tmpl yq command to query a template

The following commands are equivalent: limactl tmpl yq $TEMPLATE $EXPRESSION limactl tmpl copy --fill $TEMPLATE - | yq $EXPRESSION The new `yq` variant is clearer, but more importantly does not require that `yq` is installed. Since we already include all the code in limactl anyways, we get this functionality almost for free. Signed-off-by: Jan Dubois <[email protected]>
lima-vm · Mar 6, 2025 · be64942 · be64942
1 parent 7d5b7bd
commit be64942
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Showing 3 changed files with 105 additions and 52 deletions.
diff --git a/cmd/limactl/template.go b/cmd/limactl/template.go
@@ -12,6 +12,7 @@ import (
 	"github.com/lima-vm/lima/pkg/limatmpl"
 	"github.com/lima-vm/lima/pkg/limayaml"
 	"github.com/lima-vm/lima/pkg/store/dirnames"
+	"github.com/lima-vm/lima/pkg/yqutil"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
@@ -34,6 +35,7 @@ func newTemplateCommand() *cobra.Command {
 	templateCommand.AddCommand(
 		newTemplateCopyCommand(),
 		newTemplateValidateCommand(),
+		newTemplateYQCommand(),
 	)
 	return templateCommand
 }
@@ -71,7 +73,24 @@ func newTemplateCopyCommand() *cobra.Command {
 	return templateCopyCommand
 }
 
+func fillDefaults(tmpl *limatmpl.Template) error {
+	limaDir, err := dirnames.LimaDir()
+	if err != nil {
+		return err
+	}
+	// Load() will merge the template with override.yaml and default.yaml via FillDefaults().
+	// FillDefaults() needs the potential instance directory to validate host templates using {{.Dir}}.
+	filePath := filepath.Join(limaDir, tmpl.Name+".yaml")
+	tmpl.Config, err = limayaml.Load(tmpl.Bytes, filePath)
+	if err == nil {
+		tmpl.Bytes, err = limayaml.Marshal(tmpl.Config, false)
+	}
+	return err
+}
+
 func templateCopyAction(cmd *cobra.Command, args []string) error {
+	source := args[0]
+	target := args[1]
 	embed, err := cmd.Flags().GetBool("embed")
 	if err != nil {
 		return err
@@ -97,12 +116,12 @@ func templateCopyAction(cmd *cobra.Command, args []string) error {
 	if embed && verbatim {
 		return errors.New("--verbatim cannot be used with any of --embed, --embed-all, or --fill")
 	}
-	tmpl, err := limatmpl.Read(cmd.Context(), "", args[0])
+	tmpl, err := limatmpl.Read(cmd.Context(), "", source)
 	if err != nil {
 		return err
 	}
 	if len(tmpl.Bytes) == 0 {
-		return fmt.Errorf("don't know how to interpret %q as a template locator", args[0])
+		return fmt.Errorf("don't know how to interpret %q as a template locator", source)
 	}
 	if !verbatim {
 		if embed {
@@ -117,24 +136,11 @@ func templateCopyAction(cmd *cobra.Command, args []string) error {
 		}
 	}
 	if fill {
-		limaDir, err := dirnames.LimaDir()
-		if err != nil {
-			return err
-		}
-		// Load() will merge the template with override.yaml and default.yaml via FillDefaults().
-		// FillDefaults() needs the potential instance directory to validate host templates using {{.Dir}}.
-		filePath := filepath.Join(limaDir, tmpl.Name+".yaml")
-		tmpl.Config, err = limayaml.Load(tmpl.Bytes, filePath)
-		if err != nil {
-			return err
-		}
-		tmpl.Bytes, err = limayaml.Marshal(tmpl.Config, false)
-		if err != nil {
+		if err := fillDefaults(tmpl); err != nil {
 			return err
 		}
 	}
 	writer := cmd.OutOrStdout()
-	target := args[1]
 	if target != "-" {
 		file, err := os.OpenFile(target, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
 		if err != nil {
@@ -147,6 +153,51 @@ func templateCopyAction(cmd *cobra.Command, args []string) error {
 	return err
 }
 
+const templateYQHelp = `Use the builtin YQ evaluator to extract information from a template.
+External references are embedded and default values are filled in
+before the YQ expression is evaluated.
+
+Example:
+  limactl template yq template://default '.images[].location'
+
+The example command is equivalent to using an external yq command like this:
+  limactl template copy --fill template://default - | yq '.images[].location'
+`
+
+func newTemplateYQCommand() *cobra.Command {
+	templateYQCommand := &cobra.Command{
+		Use:   "yq TEMPLATE EXPR",
+		Short: "Query template expressions",
+		Long:  templateYQHelp,
+		Args:  WrapArgsError(cobra.ExactArgs(2)),
+		RunE:  templateYQAction,
+	}
+	return templateYQCommand
+}
+
+func templateYQAction(cmd *cobra.Command, args []string) error {
+	locator := args[0]
+	expr := args[1]
+	tmpl, err := limatmpl.Read(cmd.Context(), "", locator)
+	if err != nil {
+		return err
+	}
+	if len(tmpl.Bytes) == 0 {
+		return fmt.Errorf("don't know how to interpret %q as a template locator", locator)
+	}
+	if err := tmpl.Embed(cmd.Context(), true, true); err != nil {
+		return err
+	}
+	if err := fillDefaults(tmpl); err != nil {
+		return err
+	}
+	out, err := yqutil.EvaluateExpressionPlain(expr, string(tmpl.Bytes))
+	if err == nil {
+		_, err = fmt.Fprint(cmd.OutOrStdout(), out)
+	}
+	return err
+}
+
 func newTemplateValidateCommand() *cobra.Command {
 	templateValidateCommand := &cobra.Command{
 		Use:   "validate TEMPLATE [TEMPLATE, ...]",

diff --git a/hack/test-templates.sh b/hack/test-templates.sh
@@ -102,26 +102,15 @@ if limactl ls -q | grep -q "$NAME"; then
 	exit 1
 fi
 
-# Create ${NAME}-tmp to inspect the enabled features.
-# TODO: skip downloading and converting the image here.
-# Probably `limactl create` should have "dry run" mode that just generates `lima.yaml`.
-# shellcheck disable=SC2086
-"${LIMACTL_CREATE[@]}" ${LIMACTL_CREATE_ARGS} --set ".additionalDisks=null" --name="${NAME}-tmp" "$FILE_HOST"
-# skipping the missing yq as it is not a fatal error because networks we are looking for are not supported on windows
-if command -v yq &>/dev/null; then
-	case "$(yq '.networks[].lima' "${LIMA_HOME}/${NAME}-tmp/lima.yaml")" in
-	"shared")
-		CHECKS["vmnet"]=1
-		;;
-	"user-v2")
-		CHECKS["port-forwards"]=""
-		CHECKS["user-v2"]=1
-		;;
-	esac
-else
-	WARNING "yq not found. Skipping network checks"
-fi
-limactl rm -f "${NAME}-tmp"
+case "$(limactl tmpl yq "$FILE_HOST" '.networks[].lima')" in
+"shared")
+	CHECKS["vmnet"]=1
+	;;
+"user-v2")
+	CHECKS["port-forwards"]=""
+	CHECKS["user-v2"]=1
+	;;
+esac
 
 if [[ -n ${CHECKS["port-forwards"]} ]]; then
 	tmpconfig="$HOME_HOST/lima-config-tmp"

diff --git a/pkg/yqutil/yqutil.go b/pkg/yqutil/yqutil.go
@@ -39,25 +39,12 @@ func ValidateContent(content []byte) error {
 	return err
 }
 
-// EvaluateExpression evaluates the yq expression and returns the modified yaml.
-func EvaluateExpression(expression string, content []byte) ([]byte, error) {
+// EvaluateExpressionPlain evaluates the yq expression and returns the yq result.
+func EvaluateExpressionPlain(expression, content string) (string, error) {
 	if expression == "" {
 		return content, nil
 	}
 	logrus.Debugf("Evaluating yq expression: %q", expression)
-	formatter, err := yamlfmtBasicFormatter()
-	if err != nil {
-		return nil, err
-	}
-	// `ApplyFeatures()` is being called directly before passing content to `yqlib`.
-	// This results in `ApplyFeatures()` being called twice with `FeatureApplyBefore`:
-	// once here and once inside `formatter.Format`.
-	// Currently, calling `ApplyFeatures()` with `FeatureApplyBefore` twice is not an issue,
-	// but future changes to `yamlfmt` might cause problems if it is called twice.
-	_, contentModified, err := formatter.Features.ApplyFeatures(context.Background(), content, yamlfmt.FeatureApplyBefore)
-	if err != nil {
-		return nil, err
-	}
 	memory := logging.NewMemoryBackend(0)
 	backend := logging.AddModuleLevel(memory)
 	logging.SetBackend(backend)
@@ -68,7 +55,7 @@ func EvaluateExpression(expression string, content []byte) ([]byte, error) {
 	encoderPrefs.ColorsEnabled = false
 	encoder := yqlib.NewYamlEncoder(encoderPrefs)
 	decoder := yqlib.NewYamlDecoder(yqlib.ConfiguredYamlPreferences)
-	out, err := yqlib.NewStringEvaluator().EvaluateAll(expression, string(contentModified), encoder, decoder)
+	out, err := yqlib.NewStringEvaluator().EvaluateAll(expression, content, encoder, decoder)
 	if err != nil {
 		logger := logrus.StandardLogger()
 		for node := memory.Head(); node != nil; node = node.Next() {
@@ -90,6 +77,32 @@ func EvaluateExpression(expression string, content []byte) ([]byte, error) {
 				entry.Debug(message)
 			}
 		}
+		return "", err
+	}
+	return out, nil
+}
+
+// EvaluateExpression evaluates the yq expression and returns the output formatted with yamlfmt.
+func EvaluateExpression(expression string, content []byte) ([]byte, error) {
+	if expression == "" {
+		return content, nil
+	}
+	formatter, err := yamlfmtBasicFormatter()
+	if err != nil {
+		return nil, err
+	}
+	// `ApplyFeatures()` is being called directly before passing content to `yqlib`.
+	// This results in `ApplyFeatures()` being called twice with `FeatureApplyBefore`:
+	// once here and once inside `formatter.Format`.
+	// Currently, calling `ApplyFeatures()` with `FeatureApplyBefore` twice is not an issue,
+	// but future changes to `yamlfmt` might cause problems if it is called twice.
+	_, contentModified, err := formatter.Features.ApplyFeatures(context.Background(), content, yamlfmt.FeatureApplyBefore)
+	if err != nil {
+		return nil, err
+	}
+
+	out, err := EvaluateExpressionPlain(expression, string(contentModified))
+	if err != nil {
 		return nil, err
 	}
 	return formatter.Format([]byte(out))