rewrite to use option funcs

Signed-off-by: Paul Brousseau <object88@gmail.com>

pkg/engine/engine.go

@@ -44,11 +44,15 @@ type Engine struct {
 	config *rest.Config
 }
 
-// NewWithClient creates a new instance of client-aware Engine
-func NewWithClient(config *rest.Config) *Engine {
-	return &Engine{
-		config: config,
+// New creates a new instance of Engine with the supplied options
+func New(opts ...Option) (*Engine, error) {
+	e := &Engine{}
+	for _, opt := range opts {
+		if err := opt(e); err != nil {
+			return nil, err
+		}
 	}
+	return e, nil
 }
 
 // Render takes a chart, optional values, and value overrides, and attempts to render the Go templates.

pkg/engine/engine_test.go

@@ -22,6 +22,8 @@ import (
 	"sync"
 	"testing"
 
+	"k8s.io/client-go/rest"
+
 	"helm.sh/helm/v3/pkg/chart"
 	"helm.sh/helm/v3/pkg/chartutil"
 )
@@ -738,3 +740,97 @@ func TestRenderRecursionLimit(t *testing.T) {
 	}
 
 }
+
+func TestOptions(t *testing.T) {
+	cfg := &rest.Config{}
+
+	tcs := []struct {
+		name        string
+		opts        []Option
+		expectError bool
+		validate    func(t *testing.T, e *Engine)
+	}{
+		{
+			name:        "defaults",
+			opts:        []Option{},
+			expectError: false,
+			validate: func(t *testing.T, e *Engine) {
+				if e.config != nil || e.LintMode != false || e.Strict != false {
+					t.Errorf("Unexpected engine: %#v", e)
+				}
+			},
+		},
+		{
+			name:        "explicit-defaults",
+			opts:        []Option{WithConfig(nil), WithLintMode(false), WithStrict(false)},
+			expectError: false,
+			validate: func(t *testing.T, e *Engine) {
+				if e.config != nil || e.LintMode != false || e.Strict != false {
+					t.Errorf("Unexpected engine: %#v", e)
+				}
+			},
+		},
+		{
+			name:        "resetting-option",
+			opts:        []Option{WithLintMode(true), WithLintMode(false)},
+			expectError: false,
+			validate: func(t *testing.T, e *Engine) {
+				if e.LintMode != false {
+					t.Errorf("Incorrect lint mode")
+				}
+			},
+		},
+		{
+			name:        "with-config",
+			opts:        []Option{WithConfig(cfg)},
+			expectError: false,
+			validate: func(t *testing.T, e *Engine) {
+				if e.config != cfg {
+					t.Errorf("Set incorrect config reference")
+				}
+			},
+		},
+		{
+			name:        "with-lint-mode",
+			opts:        []Option{WithLintMode(true)},
+			expectError: false,
+			validate: func(t *testing.T, e *Engine) {
+				if e.LintMode != true {
+					t.Errorf("Did not set lint mode")
+				}
+			},
+		},
+		{
+			name:        "with-strict",
+			opts:        []Option{WithStrict(true)},
+			expectError: false,
+			validate: func(t *testing.T, e *Engine) {
+				if e.Strict != true {
+					t.Errorf("Did not set strict")
+				}
+			},
+		},
+		{
+			name:        "with-erroring-option",
+			opts:        []Option{func(*Engine) error { return fmt.Errorf("No thank you") }},
+			expectError: true,
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			e, err := New(tc.opts...)
+			if tc.expectError {
+				if err == nil {
+					t.Error("Expected error but did not get one")
+				}
+			} else {
+				if err != nil {
+					t.Errorf("Got unexpected error: %q", err)
+				} else {
+					tc.validate(t, e)
+				}
+			}
+		})
+	}
+}

pkg/engine/option.go

@@ -0,0 +1,49 @@
+/*
+Copyright The Helm Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package engine
+
+import (
+	"k8s.io/client-go/rest"
+)
+
+// Option allows specifying various settings configurable by the user within Engine
+type Option func(*Engine) error
+
+// WithConfig specifies a rest.Config for the Engine during rendering
+func WithConfig(config *rest.Config) Option {
+	return func(e *Engine) error {
+		e.config = config
+		return nil
+	}
+}
+
+// WithLintMode allows missing required funcs to not fail on render
+func WithLintMode(lintMode bool) Option {
+	return func(e *Engine) error {
+		e.LintMode = lintMode
+		return nil
+	}
+}
+
+// WithStrict will cause rendering to fail if a referenced value is not passed
+// into the render
+func WithStrict(strict bool) Option {
+	return func(e *Engine) error {
+		e.Strict = strict
+		return nil
+	}
+}