Helper Helpers

buildpack.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"os"
 	"sort"
+	"strconv"
 	"strings"
 
 	"github.com/Masterminds/semver/v3"
@@ -345,6 +346,18 @@ func (c *ConfigurationResolver) Resolve(name string) (string, bool) {
 	return "", false
 }
 
+// ResolveBool resolves a boolean value for a configuration option. Returns true for 1, t, T, TRUE, true, True. Returns
+// false for all other values or unset.
+func (c *ConfigurationResolver) ResolveBool(name string) bool {
+	s, _ := c.Resolve(name)
+	t, err := strconv.ParseBool(s)
+	if err != nil {
+		return false
+	}
+
+	return t
+}
+
 // DependencyResolver provides functionality for resolving a dependency given a collection of constraints.
 type DependencyResolver struct {
 

buildpack_test.go

@@ -130,16 +130,23 @@ func testBuildpack(t *testing.T, context spec.G, it spec.S) {
 				Configurations: []libpak.BuildpackConfiguration{
 					{Name: "TEST_KEY_1", Default: "test-default-value-1"},
 					{Name: "TEST_KEY_2", Default: "test-default-value-2"},
+					{Name: "TEST_BOOL_3", Default: "true"},
+					{Name: "TEST_BOOL_4", Default: "false"},
+					{Name: "TEST_BOOL_6", Default: "test-value"},
 				},
 			}
 		)
 
 		it.Before(func() {
 			Expect(os.Setenv("TEST_KEY_1", "test-value-1")).To(Succeed())
+			Expect(os.Setenv("TEST_BOOL_1", "true")).To(Succeed())
+			Expect(os.Setenv("TEST_BOOL_2", "false")).To(Succeed())
 		})
 
 		it.After(func() {
 			Expect(os.Unsetenv("TEST_KEY_1")).To(Succeed())
+			Expect(os.Unsetenv("TEST_BOOL_1")).To(Succeed())
+			Expect(os.Unsetenv("TEST_BOOL_2")).To(Succeed())
 		})
 
 		it("returns configured value", func() {
@@ -159,6 +166,24 @@ func testBuildpack(t *testing.T, context spec.G, it spec.S) {
 			Expect(v).To(Equal(""))
 			Expect(ok).To(BeFalse())
 		})
+
+		it("returns configured bool", func() {
+			Expect(resolver.ResolveBool("TEST_BOOL_1")).To(BeTrue())
+			Expect(resolver.ResolveBool("TEST_BOOL_2")).To(BeFalse())
+		})
+
+		it("returns default bool", func() {
+			Expect(resolver.ResolveBool("TEST_BOOL_3")).To(BeTrue())
+			Expect(resolver.ResolveBool("TEST_BOOL_4")).To(BeFalse())
+		})
+
+		it("returns false for unset", func() {
+			Expect(resolver.ResolveBool("TEST_BOOL_5")).To(BeFalse())
+		})
+
+		it("return false for invalid", func() {
+			Expect(resolver.ResolveBool("TEST_BOOL_6")).To(BeFalse())
+		})
 	})
 
 	context("DependencyResolver", func() {

sherpa/env_var.go

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2018-2020 the original author or 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
+ *
+ *      https://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 sherpa
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+// AppendToEnvVar appends a collection of values to an env var separated by a delimiter. If the env var does not already
+// exist, joins the values with the delimiter and returns the result.
+func AppendToEnvVar(name string, delimiter string, values ...string) string {
+	var e []string
+	if s, ok := os.LookupEnv(name); ok {
+		e = append(e, s)
+	}
+	e = append(e, values...)
+	return strings.Join(e, delimiter)
+}
+
+// GetEnvRequired returns the value of an environment variable if it exists, otherwise returns an error with a
+// predictable message.
+func GetEnvRequired(name string) (string, error) {
+	if s, ok := os.LookupEnv(name); ok {
+		return s, nil
+	}
+
+	return "", fmt.Errorf("$%s must be set", name)
+}
+
+// GetEnvWithWithDefault returns the value of an environment variable if it exists, otherwise returns the default.
+func GetEnvWithDefault(name string, def string) string {
+	if s, ok := os.LookupEnv(name); ok {
+		return s
+	}
+	return def
+}

sherpa/env_var_test.go

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2018-2020 the original author or 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
+ *
+ *      https://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 sherpa_test
+
+import (
+	"os"
+	"testing"
+
+	. "github.com/onsi/gomega"
+	"github.com/sclevine/spec"
+
+	"github.com/paketo-buildpacks/libpak/sherpa"
+)
+
+func testEnvVar(t *testing.T, context spec.G, it spec.S) {
+	var (
+		Expect = NewWithT(t).Expect
+	)
+
+	context("AppendToEnvVar", func() {
+
+		context("No Existing", func() {
+
+			it("append one", func() {
+				Expect(sherpa.AppendToEnvVar("TEST_KEY", "|", "test-value-2")).
+					To(Equal("test-value-2"))
+			})
+
+			it("appends multiple", func() {
+				Expect(sherpa.AppendToEnvVar("TEST_KEY", "|", "test-value-2", "test-value-3")).
+					To(Equal("test-value-2|test-value-3"))
+			})
+		})
+
+		context("With Existing", func() {
+			it.Before(func() {
+				Expect(os.Setenv("TEST_KEY", "test-value-1")).To(Succeed())
+			})
+
+			it.After(func() {
+				Expect(os.Unsetenv("TEST_KEY")).To(Succeed())
+			})
+
+			it("append one", func() {
+				Expect(sherpa.AppendToEnvVar("TEST_KEY", "|", "test-value-2")).
+					To(Equal("test-value-1|test-value-2"))
+			})
+
+			it("appends multiple", func() {
+				Expect(sherpa.AppendToEnvVar("TEST_KEY", "|", "test-value-2", "test-value-3")).
+					To(Equal("test-value-1|test-value-2|test-value-3"))
+			})
+		})
+	})
+
+	context("GetEnvRequired", func() {
+		it.Before(func() {
+			Expect(os.Setenv("TEST_KEY", "test-value")).To(Succeed())
+		})
+
+		it.After(func() {
+			Expect(os.Unsetenv("TEST_KEY")).To(Succeed())
+		})
+
+		it("returns value if set", func() {
+			Expect(sherpa.GetEnvRequired("TEST_KEY")).To(Equal("test-value"))
+		})
+
+		it("returns error if not set", func() {
+			_, err := sherpa.GetEnvRequired("ANOTHER_KEY")
+			Expect(err).To(MatchError("$ANOTHER_KEY must be set"))
+		})
+	})
+
+	context("GetEnvWithDefault", func() {
+		it.Before(func() {
+			Expect(os.Setenv("TEST_KEY", "test-value")).To(Succeed())
+		})
+
+		it.After(func() {
+			Expect(os.Unsetenv("TEST_KEY")).To(Succeed())
+		})
+
+		it("returns value if set", func() {
+			Expect(sherpa.GetEnvWithDefault("TEST_KEY", "default-value")).To(Equal("test-value"))
+		})
+
+		it("returns default value if not set", func() {
+			Expect(sherpa.GetEnvWithDefault("ANOTHER_KEY", "default-value")).To(Equal("default-value"))
+		})
+	})
+}

sherpa/init_test.go

@@ -26,6 +26,7 @@ import (
 func TestUnit(t *testing.T) {
 	suite := spec.New("libpak/sherpa", spec.Report(report.Terminal{}))
 	suite("CopyFile", testCopyFile)
+	suite("EnvVar", testEnvVar)
 	suite("FileListing", testFileListing)
 	suite("NodeJS", testNodeJS)
 	suite("Sherpa", testSherpa)