perf(context): build template funcs by mode

context/template.go

@@ -23,14 +23,18 @@ func (k Context) RunTemplate(t gomplate.Template, env map[string]any) (string, e
 	} else {
 		l.V(1).Infof("Running template: %s", t.String())
 	}
-	for _, f := range CelEnvFuncs {
-		t.CelEnvs = append(t.CelEnvs, f(k))
-	}
-	if t.Functions == nil {
-		t.Functions = make(map[string]any)
+	if t.Expression != "" {
+		for _, f := range CelEnvFuncs {
+			t.CelEnvs = append(t.CelEnvs, f(k))
+		}
 	}
-	for name, v := range TemplateFuncs {
-		t.Functions[name] = v(k)
+	if t.Template != "" {
+		if t.Functions == nil {
+			t.Functions = make(map[string]any)
+		}
+		for name, v := range TemplateFuncs {
+			t.Functions[name] = v(k)
+		}
 	}
 
 	if t.Template != "" {

context/template_test.go

@@ -4,9 +4,50 @@ import (
 	"testing"
 
 	"github.com/flanksource/gomplate/v3"
+	"github.com/google/cel-go/cel"
 	. "github.com/onsi/gomega"
 )
 
+func TestRunTemplateOnlyBuildsMatchingFunctionContexts(t *testing.T) {
+	g := NewWithT(t)
+	oldCelEnvFuncs := CelEnvFuncs
+	oldTemplateFuncs := TemplateFuncs
+	defer func() {
+		CelEnvFuncs = oldCelEnvFuncs
+		TemplateFuncs = oldTemplateFuncs
+	}()
+
+	var celBuilds int
+	var templateBuilds int
+	CelEnvFuncs = map[string]func(Context) cel.EnvOption{
+		"unused_cel_context": func(ctx Context) cel.EnvOption {
+			celBuilds++
+			return cel.Variable("unused_cel_context", cel.AnyType)
+		},
+	}
+	TemplateFuncs = map[string]func(Context) any{
+		"unused_template_context": func(ctx Context) any {
+			templateBuilds++
+			return func() string { return "unused" }
+		},
+	}
+
+	ctx := New()
+	env := map[string]any{"name": "World"}
+
+	got, err := ctx.RunTemplate(gomplate.Template{Template: "Hello {{.name}}!"}, env)
+	g.Expect(err).NotTo(HaveOccurred())
+	g.Expect(got).To(Equal("Hello World!"))
+	g.Expect(celBuilds).To(Equal(0))
+	g.Expect(templateBuilds).To(Equal(1))
+
+	ok, err := ctx.RunTemplateBool(gomplate.Template{Expression: `name == "World"`}, env)
+	g.Expect(err).NotTo(HaveOccurred())
+	g.Expect(ok).To(BeTrue())
+	g.Expect(celBuilds).To(Equal(1))
+	g.Expect(templateBuilds).To(Equal(1))
+}
+
 func TestRunTemplate(t *testing.T) {
 	t.Parallel()