Add support for SOURCE_DATE_EPOCH

internal/provider/resource_ko_build.go

@@ -6,13 +6,17 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"os"
+	"strconv"
 	"sync"
+	"time"
 
 	"github.com/awslabs/amazon-ecr-credential-helper/ecr-login"
 	"github.com/chrismellard/docker-credential-acr-env/pkg/credhelper"
 	"github.com/google/go-containerregistry/pkg/authn"
 	"github.com/google/go-containerregistry/pkg/authn/github"
 	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/google"
 	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/ko/pkg/build"
@@ -178,6 +182,16 @@ func (o *buildOptions) makeBuilder(ctx context.Context) (*build.Caching, error)
 		return nil, fmt.Errorf("unknown sbom type: %q", o.sbom)
 	}
 
+	// We read the environment variable directly here instead of plumbing it through as a provider option to keep the behavior consistent with resolve.
+	// While CreationTime is a build.Option, it is not a field in options.BuildOptions and is inferred from the environment variable when a new resolver is created.
+	if epoch := os.Getenv("SOURCE_DATE_EPOCH"); epoch != "" {
+		s, err := strconv.ParseInt(epoch, 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("the environment variable %s should be the number of seconds since January 1st 1970, 00:00 UTC, got: %w", epoch, err)
+		}
+		bo = append(bo, build.WithCreationTime(v1.Time{Time: time.Unix(s, 0)}))
+	}
+
 	b, err := build.NewGo(ctx, o.workingDir, bo...)
 	if err != nil {
 		return nil, fmt.Errorf("NewGo: %w", err)

internal/provider/resource_ko_build_test.go

@@ -128,6 +128,33 @@ func TestAccResourceKoBuild(t *testing.T) {
 			}},
 		})
 	}
+
+	t.Run("SOURCE_DATE_EPOCH", func(t *testing.T) {
+		t.Setenv("SOURCE_DATE_EPOCH", "1234567890")
+		resource.Test(t, resource.TestCase{
+			ProviderFactories: providerFactories,
+			Steps: []resource.TestStep{{
+				Config: `resource "ko_build" "foo" {
+					importpath = "github.com/ko-build/terraform-provider-ko/cmd/test"
+				}`,
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestMatchResourceAttr("ko_build.foo", "image_ref", imageRefRE),
+				),
+			}},
+		})
+	})
+	t.Run("SOURCE_DATE_EPOCH_failure", func(t *testing.T) {
+		t.Setenv("SOURCE_DATE_EPOCH", "abc123")
+		resource.Test(t, resource.TestCase{
+			ProviderFactories: providerFactories,
+			Steps: []resource.TestStep{{
+				Config: `resource "ko_build" "foo" {
+					importpath = "github.com/ko-build/terraform-provider-ko/cmd/test"
+				}`,
+				ExpectError: regexp.MustCompile("should be the number of seconds since"),
+			}},
+		})
+	})
 }
 
 func TestAccResourceKoBuild_ImageRepo(t *testing.T) {