Add support for Go build flags

There are use cases, where multiple Go build flags need to be set. However, the
environment variable to pass flags to Go build has some limits for `ldFlags`.

Add GoReleaser inspired configuration section to `.ko.yaml` to support setting
specific Go build and ldFlags to be used by the build.

Add support for environment variables `KO_GOBUILD_FLAGS` to add extra build
flags and `KO_GOBUILD_LDFLAGS` to add extra ldFlags.

README.md

@@ -123,6 +123,31 @@ baseImageOverrides:
   github.com/my-user/my-repo/cmd/foo: registry.example.com/base/for/foo
 ```
 
+### Overriding Go build settings
+
+By default, `ko` builds the binary with no additional arguments other than `--trimpath` (if available) and the ones required to name the binary accordingly. You can extend the `go build` arguments by providing extra build flags using a [GoReleaser](https://github.com/goreleaser/goreleaser) influenced `builds` configuration section in your `.ko.yaml`.
+
+```yaml
+builds:
+- id: foo
+  dir: ./foobar/foo
+  flags:
+  - -tags
+  - netgo
+  ldflags:
+  - -s -w
+  - -extldflags "-static"
+- id: bar
+  main: ./foobar/bar/main.go
+  ldflags:
+    - -s
+    - -w
+```
+
+For the build, `ko` will pick the entry based on the respective import path being used. It will be matched against the local path that is configured using `dir` and `main`. In the context of `ko`, it is fine just to specify `dir` with the intended import path.
+
+_Please note:_ Even though the configuration section is similar to the [GoReleaser `builds` section](https://goreleaser.com/customization/build/), only the `flags` and `ldflags` fields are currently supported.
+
 ## Naming Images
 
 `ko` provides a few different strategies for naming the image it pushes, to
@@ -324,6 +349,18 @@ instead:
 GOFLAGS="-ldflags=-X=main.version=1.2.3" ko publish .
 ```
 
+## How can I set multiple `ldflags`?
+
+Currently, there is a limitation that does not allow to set multiple arguments in `ldflags` using `GOFLAGS`. Using `-ldflags` multiple times also does not work. For this, `ko` supports two ways to have more complex Go build setups:
+
+- Using [`builds` section](#overriding-go-build-settings) in `.ko.yaml`.
+- Using environment variables `KO_GOBUILD_FLAGS` and `KO_GOBUILD_LDFLAGS`.
+
+```sh
+export KO_GOBUILD_LDFLAGS="-X main.buildVersion=v0.1.0 -X main.buildCommit=123456AF -X main.buildTime=2021-04-06T11:53:52Z"
+ko publish .
+```
+
 ## Why are my images all created in 1970?
 
 In order to support [reproducible builds](https://reproducible-builds.org), `ko`

go.mod

@@ -11,20 +11,18 @@ require (
 	github.com/go-training/helloworld v0.0.0-20200225145412-ba5f4379d78b
 	github.com/google/go-cmp v0.5.4
 	github.com/google/go-containerregistry v0.4.1-0.20210216200643-d81088d9983e
+	github.com/goreleaser/goreleaser v0.162.1
 	github.com/gregjones/httpcache v0.0.0-20190212212710-3befbb6ad0cc // indirect
 	github.com/mattmoor/dep-notify v0.0.0-20190205035814-a45dec370a17
 	github.com/onsi/gomega v1.10.3 // indirect
-	github.com/spf13/cobra v1.0.0
+	github.com/spf13/cobra v1.1.3
 	github.com/spf13/jwalterweatherman v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.5
-	github.com/spf13/viper v1.4.0
-	golang.org/x/crypto v0.0.0-20201002170205-7f63de1d35b0 // indirect
+	github.com/spf13/viper v1.7.1
 	golang.org/x/mod v0.4.1 // indirect
 	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a
-	golang.org/x/sys v0.0.0-20210216163648-f7da38b97c65 // indirect
 	golang.org/x/tools v0.1.0
-	gopkg.in/check.v1 v1.0.0-20200902074654-038fdea0a05b // indirect
-	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776
+	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
 	gotest.tools/v3 v3.0.2 // indirect
 	k8s.io/apimachinery v0.19.7
 	k8s.io/cli-runtime v0.19.7

pkg/build/gobuild.go

@@ -38,6 +38,7 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/mutate"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
 	"github.com/google/go-containerregistry/pkg/v1/types"
+	goreleaserCfg "github.com/goreleaser/goreleaser/pkg/config"
 )
 
 const (
@@ -64,7 +65,7 @@ For more information see:
 // GetBase takes an importpath and returns a base image.
 type GetBase func(context.Context, string) (Result, error)
 
-type builder func(context.Context, string, v1.Platform, bool) (string, error)
+type builder func(context.Context, string, v1.Platform, []string) (string, error)
 
 type buildContext interface {
 	Import(path string, srcDir string, mode gb.ImportMode) (*gb.Package, error)
@@ -80,6 +81,7 @@ type gobuild struct {
 	creationTime         v1.Time
 	build                builder
 	disableOptimizations bool
+	buildCfgOverrides    map[string]goreleaserCfg.Build
 	mod                  *modules
 	buildContext         buildContext
 	platformMatcher      *platformMatcher
@@ -94,6 +96,7 @@ type gobuildOpener struct {
 	creationTime         v1.Time
 	build                builder
 	disableOptimizations bool
+	buildCfgOverrides    map[string]goreleaserCfg.Build
 	mod                  *modules
 	buildContext         buildContext
 	platform             string
@@ -113,6 +116,7 @@ func (gbo *gobuildOpener) Open() (Interface, error) {
 		creationTime:         gbo.creationTime,
 		build:                gbo.build,
 		disableOptimizations: gbo.disableOptimizations,
+		buildCfgOverrides:    gbo.buildCfgOverrides,
 		mod:                  gbo.mod,
 		buildContext:         gbo.buildContext,
 		labels:               gbo.labels,
@@ -303,19 +307,16 @@ func platformToString(p v1.Platform) string {
 	return fmt.Sprintf("%s/%s", p.OS, p.Architecture)
 }
 
-func build(ctx context.Context, ip string, platform v1.Platform, disableOptimizations bool) (string, error) {
+func build(ctx context.Context, ip string, platform v1.Platform, buildArgs []string) (string, error) {
 	tmpDir, err := ioutil.TempDir("", "ko")
 	if err != nil {
 		return "", err
 	}
 	file := filepath.Join(tmpDir, "out")
 
-	args := make([]string, 0, 7)
+	args := make([]string, 0, 5+len(buildArgs))
 	args = append(args, "build")
-	if disableOptimizations {
-		// Disable optimizations (-N) and inlining (-l).
-		args = append(args, "-gcflags", "all=-N -l")
-	}
+	args = append(args, buildArgs...)
 	args = append(args, "-o", file)
 	args = addGo113TrimPathFlag(args)
 	args = append(args, ip)
@@ -520,6 +521,37 @@ func (g *gobuild) tarKoData(ref reference) (*bytes.Buffer, error) {
 	return buf, walkRecursive(tw, root, kodataRoot)
 }
 
+func (g *gobuild) buildArgs(ip string) []string {
+	var args []string
+
+	if g.disableOptimizations {
+		// Disable optimizations (-N) and inlining (-l).
+		args = append(args, "-gcflags", "all=-N -l")
+	}
+
+	var buildFlags []string
+	if additionalBuildFlags, ok := os.LookupEnv("KO_GOBUILD_FLAGS"); ok {
+		buildFlags = append(buildFlags, strings.Split(additionalBuildFlags, " ")...)
+	}
+
+	var buildLdFlags []string
+	if additionalBuildLdFlags, ok := os.LookupEnv("KO_GOBUILD_LDFLAGS"); ok {
+		buildLdFlags = append(buildLdFlags, strings.Split(additionalBuildLdFlags, " ")...)
+	}
+
+	if buildCfg, ok := g.buildCfgOverrides[ip]; ok {
+		buildFlags = append(buildFlags, buildCfg.Flags...)
+		buildLdFlags = append(buildLdFlags, buildCfg.Ldflags...)
+	}
+
+	args = append(args, buildFlags...)
+	if len(buildLdFlags) > 0 {
+		args = append(args, fmt.Sprintf("-ldflags=%s", strings.Join(buildLdFlags, " ")))
+	}
+
+	return args
+}
+
 func (g *gobuild) buildOne(ctx context.Context, s string, base v1.Image, platform *v1.Platform) (v1.Image, error) {
 	ref := newRef(s)
 
@@ -536,7 +568,7 @@ func (g *gobuild) buildOne(ctx context.Context, s string, base v1.Image, platfor
 	}
 
 	// Do the build into a temporary file.
-	file, err := g.build(ctx, ref.Path(), *platform, g.disableOptimizations)
+	file, err := g.build(ctx, ref.Path(), *platform, g.buildArgs(ref.Path()))
 	if err != nil {
 		return nil, err
 	}

pkg/build/gobuild_test.go

@@ -132,7 +132,7 @@ func TestGoBuildIsSupportedRefWithModules(t *testing.T) {
 }
 
 // A helper method we use to substitute for the default "build" method.
-func writeTempFile(_ context.Context, s string, _ v1.Platform, _ bool) (string, error) {
+func writeTempFile(_ context.Context, s string, _ v1.Platform, _ []string) (string, error) {
 	tmpDir, err := ioutil.TempDir("", "ko")
 	if err != nil {
 		return "", err

pkg/build/options.go

@@ -16,6 +16,7 @@ package build
 
 import (
 	v1 "github.com/google/go-containerregistry/pkg/v1"
+	goreleaserCfg "github.com/goreleaser/goreleaser/pkg/config"
 )
 
 // WithBaseImages is a functional option for overriding the base images
@@ -45,6 +46,13 @@ func WithDisabledOptimizations() Option {
 	}
 }
 
+func WithGoReleaserBuildConfig(buildCfgOverrides map[string]goreleaserCfg.Build) Option {
+	return func(gbo *gobuildOpener) error {
+		gbo.buildCfgOverrides = buildCfgOverrides
+		return nil
+	}
+}
+
 // WithPlatforms is a functional option for building certain platforms for
 // multi-platform base images. To build everything from the base, use "all",
 // otherwise use a comma-separated list of platform specs, i.e.:

pkg/commands/config.go

@@ -20,6 +20,7 @@ import (
 	"log"
 	"os"
 	"os/signal"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"syscall"
@@ -31,12 +32,14 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/remote"
 	"github.com/google/go-containerregistry/pkg/v1/types"
 	"github.com/google/ko/pkg/build"
+	goreleaserCfg "github.com/goreleaser/goreleaser/pkg/config"
 	"github.com/spf13/viper"
 )
 
 var (
 	defaultBaseImage   name.Reference
 	baseImageOverrides map[string]name.Reference
+	buildCfgOverrides  map[string]goreleaserCfg.Build
 )
 
 func getBaseImage(platform string) build.GetBase {
@@ -160,4 +163,30 @@ func init() {
 		}
 		baseImageOverrides[k] = bi
 	}
+
+	var builds []goreleaserCfg.Build
+	if err := viper.UnmarshalKey("builds", &builds); err != nil {
+		log.Fatalf("configuration section 'builds' cannot be parsed")
+	}
+
+	buildCfgOverrides = make(map[string]goreleaserCfg.Build)
+	for _, build := range builds {
+		path := build.Dir
+		if len(path) == 0 {
+			path = "./"
+		}
+
+		if len(build.Main) > 0 {
+			if mainDir := filepath.Dir(build.Main); mainDir != "." {
+				path = path + string(filepath.Separator) + mainDir
+			}
+		}
+
+		importPath, err := qualifyLocalImport(path)
+		if err != nil {
+			log.Fatalf("failed to create qualified import path using path %s", path)
+		}
+
+		buildCfgOverrides[importPath] = build
+	}
 }

pkg/commands/resolver.go

@@ -93,6 +93,11 @@ func gobuildOptions(bo *options.BuildOptions) ([]build.Option, error) {
 		}
 		opts = append(opts, build.WithLabel(parts[0], parts[1]))
 	}
+
+	if len(buildCfgOverrides) > 0 {
+		opts = append(opts, build.WithGoReleaserBuildConfig(buildCfgOverrides))
+	}
+
 	return opts, nil
 }