build: handle missing build contexts (#6141)

Before this change, if you specified a directory that doesn't
exist as your docker_build context, you would get an empty build context.

After this change, if you specify a directory that doesn't exist,
you get a build-time error. You can use "-" to specify an empty build context.

this is a breaking change, but i think makes us more consistent with
how the docker cli works.

fixes #3897
fixes #6125

Signed-off-by: Nick Santos <nick.santos@docker.com>

internal/build/container_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/tilt-dev/tilt/internal/container"
 	"github.com/tilt-dev/tilt/internal/docker"
@@ -145,3 +146,42 @@ RUN echo 'failed to create LLB definition: failed commit on ref "unknown-sha256:
 	assert.Contains(t, out.String(), "[1/2] FROM docker.io/library/alpine")                     // buildkit-style output
 	assert.True(t, regexp.MustCompile("Step 1/[0-9]+ : FROM alpine").MatchString(out.String())) // Legacy output
 }
+
+func TestDockerBuildEmptyContext(t *testing.T) {
+	f := newDockerBuildFixture(t)
+
+	df := dockerfile.Dockerfile(`
+FROM alpine
+`)
+
+	spec := v1alpha1.DockerImageSpec{
+		DockerfileContents: df.String(),
+		Context:            "-",
+	}
+	refs, _, err := f.b.BuildImage(f.ctx, f.ps, f.getNameFromTest(), spec,
+		defaultCluster,
+		nil,
+		model.EmptyMatcher)
+	require.NoError(t, err)
+	f.assertImageHasLabels(refs.LocalRef, docker.BuiltLabelSet)
+}
+
+func TestDockerBuildMissingContext(t *testing.T) {
+	f := newDockerBuildFixture(t)
+
+	df := dockerfile.Dockerfile(`
+FROM alpine
+`)
+
+	spec := v1alpha1.DockerImageSpec{
+		DockerfileContents: df.String(),
+		Context:            "unknown-dir",
+	}
+	_, _, err := f.b.BuildImage(f.ctx, f.ps, f.getNameFromTest(), spec,
+		defaultCluster,
+		nil,
+		model.EmptyMatcher)
+	if assert.Error(t, err) {
+		assert.Contains(t, err.Error(), "reading build context: stat unknown-dir: no such file or directory")
+	}
+}

internal/build/docker_builder.go

@@ -206,6 +206,27 @@ func (d *DockerBuilder) BuildImage(ctx context.Context, ps *PipelineState, refs
 func (d *DockerBuilder) buildToDigest(ctx context.Context, spec v1alpha1.DockerImageSpec, filter model.PathMatcher, allowBuildkit bool) (digest.Digest, []v1alpha1.DockerImageStageStatus, error) {
 	var contextReader io.Reader
 
+	buildContext := spec.Context
+
+	// Treat context: "-" as an empty context.
+	if buildContext == "-" {
+		emptyContextDir, err := os.MkdirTemp("", "tilt-dockercontext-")
+		if err != nil {
+			return "", nil, fmt.Errorf("creating context directory: %v", err)
+		}
+
+		defer func() {
+			_ = os.RemoveAll(emptyContextDir)
+		}()
+
+		buildContext = emptyContextDir
+	}
+
+	_, err := os.Stat(buildContext)
+	if err != nil {
+		return "", nil, fmt.Errorf("reading build context: %v", err)
+	}
+
 	// Buildkit allows us to use a fs sync server instead of uploading up-front.
 	useFSSync := allowBuildkit && d.dCli.BuilderVersion() == types.BuilderBuildKit
 	if !useFSSync {
@@ -217,7 +238,7 @@ func (d *DockerBuilder) buildToDigest(ctx context.Context, spec v1alpha1.DockerI
 		go func(ctx context.Context) {
 			paths := []PathMapping{
 				{
-					LocalPath:     spec.Context,
+					LocalPath:     buildContext,
 					ContainerPath: "/",
 				},
 			}
@@ -242,7 +263,7 @@ func (d *DockerBuilder) buildToDigest(ctx context.Context, spec v1alpha1.DockerI
 		if err != nil {
 			return "", nil, err
 		}
-		options.SyncedDirs = toSyncedDirs(spec.Context, dockerfileDir, filter)
+		options.SyncedDirs = toSyncedDirs(buildContext, dockerfileDir, filter)
 		options.Dockerfile = DockerfileName
 
 		defer func() {

internal/engine/buildcontrol/docker_compose_build_and_deployer_test.go

@@ -4,6 +4,7 @@ import (
 	"archive/tar"
 	"context"
 	"fmt"
+	"os"
 	"testing"
 
 	"github.com/jonboulle/clockwork"
@@ -88,7 +89,7 @@ func TestTiltBuildsImageWithTag(t *testing.T) {
 
 	refWithTag := "gcr.io/foo:bar"
 	iTarget := model.MustNewImageTarget(container.MustParseSelector(refWithTag)).
-		WithBuildDetails(model.DockerBuild{})
+		WithBuildDetails(model.DockerBuild{DockerImageSpec: v1alpha1.DockerImageSpec{Context: "-"}})
 	manifest := manifestbuilder.New(f, "fe").
 		WithDockerCompose().
 		WithImageTarget(iTarget).
@@ -200,6 +201,10 @@ func newDCBDFixture(t *testing.T) *dcbdFixture {
 
 	f := tempdir.NewTempDirFixture(t)
 
+	// empty dirs for build contexts
+	_ = os.Mkdir(f.JoinPath("sancho"), 0777)
+	_ = os.Mkdir(f.JoinPath("sancho-base"), 0777)
+
 	dir := dirs.NewTiltDevDirAt(f.Path())
 	dcCli := dockercompose.NewFakeDockerComposeClient(t, ctx)
 	dCli := docker.NewFakeClient()

internal/engine/buildcontrol/image_build_and_deployer_test.go

@@ -4,6 +4,7 @@ import (
 	"archive/tar"
 	"context"
 	"fmt"
+	"os"
 	"sort"
 	"strings"
 	"testing"
@@ -1090,6 +1091,11 @@ type ibdFixture struct {
 
 func newIBDFixture(t *testing.T, env clusterid.Product) *ibdFixture {
 	f := tempdir.NewTempDirFixture(t)
+
+	// empty dirs for build contexts
+	_ = os.Mkdir(f.JoinPath("sancho"), 0777)
+	_ = os.Mkdir(f.JoinPath("sancho-base"), 0777)
+
 	dir := dirs.NewTiltDevDirAt(f.Path())
 
 	dockerClient := docker.NewFakeClient()