Generalize instructions for entrypoint and working directory

Summary:
Introduce new `build.EntryPoint` and `build.WorkingDirectory`
instructions to allow configuration to inject them instead of hard
coding their generation in the Docker compiler.

Simplified the Docker compiler to simply iterate over build phases as
returned by a new function `build.Phases()`.

Depends on D990

Test Plan: Run `go test ./...`.

Reviewers: thcipriani, demon, hashar, #release-engineering-team

Reviewed By: thcipriani, #release-engineering-team

Tags: #release-engineering-team

Differential Revision: https://phabricator.wikimedia.org/D991

3 files changed, 29 insertions, 17 deletions

diff --git a/docker/compiler.go b/docker/compiler.go
index 5929692..b0d5dce 100644
--- a/docker/compiler.go
+++ b/docker/compiler.go
@@ -5,7 +5,6 @@ package docker
 
 import (
 	"bytes"
-	"strings"
 
 	"phabricator.wikimedia.org/source/blubber/build"
 	"phabricator.wikimedia.org/source/blubber/config"
@@ -61,22 +60,8 @@ func compileStage(buffer *bytes.Buffer, stage string, vcfg *config.VariantConfig
 
 	writeln(buffer, "FROM ", baseAndStage)
 
-	compilePhase(buffer, vcfg, build.PhasePrivileged)
-
-	compilePhase(buffer, vcfg, build.PhasePrivilegeDropped)
-
-	if vcfg.Lives.In != "" {
-		writeln(buffer, "WORKDIR ", vcfg.Lives.In)
-	}
-
-	compilePhase(buffer, vcfg, build.PhasePreInstall)
-
-	compilePhase(buffer, vcfg, build.PhaseInstall)
-
-	compilePhase(buffer, vcfg, build.PhasePostInstall)
-
-	if len(vcfg.EntryPoint) > 0 {
-		writeln(buffer, "ENTRYPOINT [\"", strings.Join(vcfg.EntryPoint, "\", \""), "\"]")
+	for _, phase := range build.Phases() {
+		compilePhase(buffer, vcfg, phase)
 	}
 }
 
diff --git a/docker/instructions.go b/docker/instructions.go
index c031d01..8463b0e 100644
--- a/docker/instructions.go
+++ b/docker/instructions.go
@@ -31,6 +31,10 @@ func NewInstruction(bi build.Instruction) (Instruction, error) {
 			i.flags = []string{"from"}
 		}
 
+	case build.EntryPoint:
+		i.name = "ENTRYPOINT"
+		i.array = true
+
 	case build.Env:
 		i.name = "ENV"
 		i.separator = " "
@@ -45,6 +49,9 @@ func NewInstruction(bi build.Instruction) (Instruction, error) {
 	case build.Volume:
 		i.name = "VOLUME"
 		i.array = true
+
+	case build.WorkingDirectory:
+		i.name = "WORKDIR"
 	}
 
 	if i.name == "" {
diff --git a/docker/instructions_test.go b/docker/instructions_test.go
index 37eeaf1..6215841 100644
--- a/docker/instructions_test.go
+++ b/docker/instructions_test.go
@@ -61,6 +61,16 @@ func TestCopyFrom(t *testing.T) {
 	}
 }
 
+func TestEntryPoint(t *testing.T) {
+	i := build.EntryPoint{[]string{"foo", "bar"}}
+
+	di, err := docker.NewInstruction(i)
+
+	if assert.NoError(t, err) {
+		assert.Equal(t, "ENTRYPOINT [\"foo\", \"bar\"]\n", di.Compile())
+	}
+}
+
 func TestEnv(t *testing.T) {
 	i := build.Env{map[string]string{"foo": "bar", "bar": "foo"}}
 
@@ -101,6 +111,16 @@ func TestVolume(t *testing.T) {
 	}
 }
 
+func TestWorkingDirectory(t *testing.T) {
+	i := build.WorkingDirectory{"/foo/dir"}
+
+	di, err := docker.NewInstruction(i)
+
+	if assert.NoError(t, err) {
+		assert.Equal(t, "WORKDIR \"/foo/dir\"\n", di.Compile())
+	}
+}
+
 func TestEscapeRun(t *testing.T) {
 	i := build.Run{"/bin/true\nRUN echo HACKED!", []string{}}