chore: expression for vars value (#7411)

apis/apps/v1alpha1/type.go

@@ -979,6 +979,24 @@ type EnvVar struct {
 	//
 	// +optional
 	ValueFrom *VarSource `json:"valueFrom,omitempty"`
+
+	// A Go template expression that will be applied to the resolved value of the var.
+	//
+	// The expression will only be evaluated if the var is successfully resolved to a non-credential value.
+	//
+	// The resolved value can be accessed by its name within the expression, system vars and other user-defined
+	// non-credential vars can be used within the expression in the same way.
+	// Notice that, when accessing vars by its name, you should replace all the "-" in the name with "_", because of
+	// that "-" is not a valid identifier in Go.
+	//
+	// All expressions are evaluated in the order the vars are defined. If a var depends on any vars that also
+	// have expressions defined, be careful about the evaluation order as it may use intermediate values.
+	//
+	// The result of evaluation will be used as the final value of the var. If the expression fails to evaluate,
+	// the resolving of var will also be considered failed.
+	//
+	// +optional
+	Expression *string `json:"expression,omitempty"`
 }
 
 // VarSource represents a source for the value of an EnvVar.

config/crd/bases/apps.kubeblocks.io_componentdefinitions.yaml

@@ -13348,6 +13348,23 @@ spec:
                   description: EnvVar represents a variable present in the env of
                     Pod/Action or the template of config/script.
                   properties:
+                    expression:
+                      description: "A Go template expression that will be applied
+                        to the resolved value of the var. \n The expression will only
+                        be evaluated if the var is successfully resolved to a non-credential
+                        value. \n The resolved value can be accessed by its name within
+                        the expression, system vars and other user-defined non-credential
+                        vars can be used within the expression in the same way. Notice
+                        that, when accessing vars by its name, you should replace
+                        all the \"-\" in the name with \"_\", because of that \"-\"
+                        is not a valid identifier in Go. \n All expressions are evaluated
+                        in the order the vars are defined. If a var depends on any
+                        vars that also have expressions defined, be careful about
+                        the evaluation order as it may use intermediate values. \n
+                        The result of evaluation will be used as the final value of
+                        the var. If the expression fails to evaluate, the resolving
+                        of var will also be considered failed."
+                      type: string
                     name:
                       description: Name of the variable. Must be a C_IDENTIFIER.
                       type: string

deploy/helm/crds/apps.kubeblocks.io_componentdefinitions.yaml

@@ -13348,6 +13348,23 @@ spec:
                   description: EnvVar represents a variable present in the env of
                     Pod/Action or the template of config/script.
                   properties:
+                    expression:
+                      description: "A Go template expression that will be applied
+                        to the resolved value of the var. \n The expression will only
+                        be evaluated if the var is successfully resolved to a non-credential
+                        value. \n The resolved value can be accessed by its name within
+                        the expression, system vars and other user-defined non-credential
+                        vars can be used within the expression in the same way. Notice
+                        that, when accessing vars by its name, you should replace
+                        all the \"-\" in the name with \"_\", because of that \"-\"
+                        is not a valid identifier in Go. \n All expressions are evaluated
+                        in the order the vars are defined. If a var depends on any
+                        vars that also have expressions defined, be careful about
+                        the evaluation order as it may use intermediate values. \n
+                        The result of evaluation will be used as the final value of
+                        the var. If the expression fails to evaluate, the resolving
+                        of var will also be considered failed."
+                      type: string
                     name:
                       description: Name of the variable. Must be a C_IDENTIFIER.
                       type: string

docs/developer_docs/api-reference/cluster.md

@@ -11335,6 +11335,27 @@ VarSource
 <p>Source for the variable&rsquo;s value. Cannot be used if value is not empty.</p>
 </td>
 </tr>
+<tr>
+<td>
+<code>expression</code><br/>
+<em>
+string
+</em>
+</td>
+<td>
+<em>(Optional)</em>
+<p>A Go template expression that will be applied to the resolved value of the var.</p>
+<p>The expression will only be evaluated if the var is successfully resolved to a non-credential value.</p>
+<p>The resolved value can be accessed by its name within the expression, system vars and other user-defined
+non-credential vars can be used within the expression in the same way.
+Notice that, when accessing vars by its name, you should replace all the &ldquo;-&rdquo; in the name with &ldquo;_&rdquo;, because of
+that &ldquo;-&rdquo; is not a valid identifier in Go.</p>
+<p>All expressions are evaluated in the order the vars are defined. If a var depends on any vars that also
+have expressions defined, be careful about the evaluation order as it may use intermediate values.</p>
+<p>The result of evaluation will be used as the final value of the var. If the expression fails to evaluate,
+the resolving of var will also be considered failed.</p>
+</td>
+</tr>
 </tbody>
 </table>
 <h3 id="apps.kubeblocks.io/v1alpha1.EnvVarRef">EnvVarRef

pkg/controller/component/vars.go

@@ -28,7 +28,9 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"text/template"
 
+	"github.com/Masterminds/sprig/v3"
 	"golang.org/x/exp/maps"
 	corev1 "k8s.io/api/core/v1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
@@ -45,6 +47,7 @@ import (
 
 var (
 	varReferenceRegExp = regexp.MustCompile(`\$\(([^)]+)\)`)
+	varTemplate        = template.New("vars").Option("missingkey=error").Funcs(sprig.TxtFuncMap())
 )
 
 func VarReferenceRegExp() *regexp.Regexp {
@@ -154,6 +157,9 @@ func resolveBuiltinNObjectRefVars(ctx context.Context, cli client.Reader, synthe
 		return nil, nil, err
 	}
 	vars = append(vars, vars1...)
+	if err = evaluateObjectVarsExpression(definedVars, vars2, &vars); err != nil {
+		return nil, nil, err
+	}
 	return vars, vars2, nil
 }
 
@@ -373,6 +379,75 @@ func buildEnv4UserDefined(annotations map[string]string) ([]corev1.EnvVar, error
 	return vars, nil
 }
 
+func evaluateObjectVarsExpression(definedVars []appsv1alpha1.EnvVar, credentialVars []corev1.EnvVar, vars *[]corev1.EnvVar) error {
+	var (
+		isValues = make(map[string]bool)
+		values   = make(map[string]string)
+	)
+	normalize := func(name string) string {
+		return strings.ReplaceAll(name, "-", "_")
+	}
+	for _, v := range [][]corev1.EnvVar{*vars, credentialVars} {
+		for _, vv := range v {
+			if vv.ValueFrom == nil {
+				isValues[vv.Name] = true
+				values[normalize(vv.Name)] = vv.Value
+			} else {
+				isValues[vv.Name] = false
+			}
+		}
+	}
+
+	evaluable := func(v appsv1alpha1.EnvVar) bool {
+		if v.Expression == nil || len(*v.Expression) == 0 {
+			return false
+		}
+		isValue, ok := isValues[v.Name]
+		// !ok is for vars that defined and resolved successfully, but have nil value.
+		return !ok || isValue
+	}
+
+	update := func(name, value string) {
+		if val, exist := values[normalize(name)]; exist {
+			if val != value {
+				for i := range *vars {
+					if (*vars)[i].Name == name {
+						(*vars)[i].Value = value
+						break
+					}
+				}
+			}
+		} else {
+			// TODO: insert the var to keep orders?
+			*vars = append(*vars, corev1.EnvVar{Name: name, Value: value})
+		}
+		values[normalize(name)] = value
+	}
+
+	eval := func(v appsv1alpha1.EnvVar) error {
+		if !evaluable(v) {
+			return nil
+		}
+		tpl, err := varTemplate.Parse(*v.Expression)
+		if err != nil {
+			return err
+		}
+		var buf strings.Builder
+		if err = tpl.Execute(&buf, values); err != nil {
+			return err
+		}
+		update(v.Name, buf.String())
+		return nil
+	}
+
+	for _, v := range definedVars {
+		if err := eval(v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func resolveClusterObjectRefVars(ctx context.Context, cli client.Reader, synthesizedComp *SynthesizedComponent,
 	definedVars []appsv1alpha1.EnvVar) ([]corev1.EnvVar, []corev1.EnvVar, error) {
 	if synthesizedComp == nil {