feat: use more specific codes during detect

cmd/exit.go

@@ -12,9 +12,10 @@ const (
 	CodeInvalidArgs = 3
 	// 4: CodeInvalidEnv
 	// 5: CodeNotFound
-	CodeFailedDetect = 6
-	CodeFailedBuild  = 7
-	CodeFailedLaunch = 8
+	CodeFailedDetect           = 100
+	CodeFailedDetectWithErrors = 101
+	CodeFailedBuild            = 7
+	CodeFailedLaunch           = 8
 	// 9: CodeFailedUpdate
 	CodeFailedSave   = 10
 	CodeIncompatible = 11

cmd/lifecycle/detector.go

@@ -79,11 +79,17 @@ func (da detectArgs) detect() (lifecycle.BuildpackGroup, lifecycle.BuildPlan, er
 		Logger:        cmd.Logger,
 	})
 	if err != nil {
-		if err == lifecycle.ErrFail {
+		switch err {
+		case lifecycle.ErrFailedDetection:
 			cmd.Logger.Error("No buildpack groups passed detection.")
 			cmd.Logger.Error("Please check that you are running against the correct path.")
+			return lifecycle.BuildpackGroup{}, lifecycle.BuildPlan{}, cmd.FailErrCode(err, cmd.CodeFailedDetect, "detect")
+		case lifecycle.ErrBuildpack:
+			cmd.Logger.Error("No buildpack groups passed detection.")
+			return lifecycle.BuildpackGroup{}, lifecycle.BuildPlan{}, cmd.FailErrCode(err, cmd.CodeFailedDetectWithErrors, "detect")
+		default:
+			return lifecycle.BuildpackGroup{}, lifecycle.BuildPlan{}, cmd.FailErrCode(err, 1, "detect")
 		}
-		return lifecycle.BuildpackGroup{}, lifecycle.BuildPlan{}, cmd.FailErrCode(err, cmd.CodeFailedDetect, "detect")
 	}
 
 	return group, plan, nil

detector.go

@@ -20,7 +20,8 @@ const (
 	EnvBuildpackDir = "CNB_BUILDPACK_DIR"
 )
 
-var ErrFail = errors.New("no buildpacks participating")
+var ErrFailedDetection = errors.New("no buildpacks participating")
+var ErrBuildpack = errors.New("buildpack(s) failed with err")
 
 type BuildPlan struct {
 	Entries []BuildPlanEntry `toml:"entries"`
@@ -83,6 +84,7 @@ func (c *DetectConfig) process(done []Buildpack) ([]Buildpack, []BuildPlanEntry,
 
 	results := detectResults{}
 	detected := true
+	buildpackErr := false
 	for i, bp := range done {
 		run := runs[i]
 		switch run.Code {
@@ -98,14 +100,19 @@ func (c *DetectConfig) process(done []Buildpack) ([]Buildpack, []BuildPlanEntry,
 			detected = detected && bp.Optional
 		case -1:
 			c.Logger.Debugf("err:  %s", bp)
+			buildpackErr = true
 			detected = detected && bp.Optional
 		default:
 			c.Logger.Debugf("err:  %s (%d)", bp, run.Code)
+			buildpackErr = true
 			detected = detected && bp.Optional
 		}
 	}
 	if !detected {
-		return nil, nil, ErrFail
+		if buildpackErr {
+			return nil, nil, ErrBuildpack
+		}
+		return nil, nil, ErrFailedDetection
 	}
 
 	i := 0
@@ -159,7 +166,7 @@ func (c *DetectConfig) runTrial(i int, trial detectTrial) (depMap, detectTrial,
 			retry = true
 			if !bp.Optional {
 				c.Logger.Debugf("fail: %s requires %s", bp, name)
-				return ErrFail
+				return ErrFailedDetection
 			}
 			c.Logger.Debugf("skip: %s requires %s", bp, name)
 			trial = trial.remove(bp)
@@ -172,7 +179,7 @@ func (c *DetectConfig) runTrial(i int, trial detectTrial) (depMap, detectTrial,
 			retry = true
 			if !bp.Optional {
 				c.Logger.Debugf("fail: %s provides unused %s", bp, name)
-				return ErrFail
+				return ErrFailedDetection
 			}
 			c.Logger.Debugf("skip: %s provides unused %s", bp, name)
 			trial = trial.remove(bp)
@@ -184,7 +191,7 @@ func (c *DetectConfig) runTrial(i int, trial detectTrial) (depMap, detectTrial,
 
 	if len(trial) == 0 {
 		c.Logger.Debugf("fail: no viable buildpacks in group")
-		return nil, nil, ErrFail
+		return nil, nil, ErrFailedDetection
 	}
 	return deps, trial, nil
 }
@@ -301,10 +308,14 @@ func (bo BuildpackOrder) Detect(c *DetectConfig) (BuildpackGroup, BuildPlan, err
 
 func (bo BuildpackOrder) detect(done, next []Buildpack, optional bool, wg *sync.WaitGroup, c *DetectConfig) ([]Buildpack, []BuildPlanEntry, error) {
 	ngroup := BuildpackGroup{Group: next}
+	buildpackErr := false
 	for _, group := range bo {
 		// FIXME: double-check slice safety here
 		found, plan, err := group.append(ngroup).detect(done, wg, c)
-		if err == ErrFail {
+		if err == ErrBuildpack {
+			buildpackErr = true
+		}
+		if err == ErrFailedDetection || err == ErrBuildpack {
 			wg = &sync.WaitGroup{}
 			continue
 		}
@@ -313,7 +324,11 @@ func (bo BuildpackOrder) detect(done, next []Buildpack, optional bool, wg *sync.
 	if optional {
 		return ngroup.detect(done, wg, c)
 	}
-	return nil, nil, ErrFail
+
+	if buildpackErr {
+		return nil, nil, ErrBuildpack
+	}
+	return nil, nil, ErrFailedDetection
 }
 
 func hasID(bps []Buildpack, id string) bool {

detector_test.go

@@ -80,7 +80,7 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 			_, _, err := lifecycle.BuildpackOrder{
 				{Group: []lifecycle.Buildpack{{ID: "E", Version: "v1"}}},
 			}.Detect(config)
-			if err != lifecycle.ErrFail {
+			if err != lifecycle.ErrFailedDetection {
 				t.Fatalf("Unexpected error:\n%s\n", err)
 			}
 
@@ -127,7 +127,7 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 
 		it("should fail if the group is empty", func() {
 			_, _, err := lifecycle.BuildpackOrder([]lifecycle.BuildpackGroup{{}}).Detect(config)
-			if err != lifecycle.ErrFail {
+			if err != lifecycle.ErrFailedDetection {
 				t.Fatalf("Unexpected error:\n%s\n", err)
 			}
 
@@ -148,7 +148,7 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 					{ID: "B", Version: "v1", Optional: true},
 				}},
 			}.Detect(config)
-			if err != lifecycle.ErrFail {
+			if err != lifecycle.ErrFailedDetection {
 				t.Fatalf("Unexpected error:\n%s\n", err)
 			}
 
@@ -163,6 +163,29 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 			}
 		})
 
+		it("should fail with specific error if any bp detect fails in an unexpected way", func() {
+			mkappfile("100", "detect-status")
+			mkappfile("0", "detect-status-A-v1")
+			mkappfile("127", "detect-status-B-v1")
+			_, _, err := lifecycle.BuildpackOrder{
+				{Group: []lifecycle.Buildpack{
+					{ID: "A", Version: "v1", Optional: false},
+					{ID: "B", Version: "v1", Optional: false},
+				}},
+			}.Detect(config)
+			if err != lifecycle.ErrBuildpack {
+				t.Fatalf("Unexpected error:\n%s\n", err)
+			}
+
+			if s := allLogs(logHandler); !strings.HasSuffix(s,
+				"======== Results ========\n"+
+					"pass: A@v1\n"+
+					"err:  B@v1 (127)\n",
+			) {
+				t.Fatalf("Unexpected log:\n%s\n", s)
+			}
+		})
+
 		it("should select an appropriate env type", func() {
 			mkappfile("0", "detect-status-A-v1.clear", "detect-status-B-v1")
 
@@ -297,7 +320,7 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 						{ID: "C", Version: "v1"},
 					}},
 				}.Detect(config)
-				if err != lifecycle.ErrFail {
+				if err != lifecycle.ErrFailedDetection {
 					t.Fatalf("Unexpected error:\n%s\n", err)
 				}
 
@@ -325,7 +348,7 @@ func testDetector(t *testing.T, when spec.G, it spec.S) {
 						{ID: "C", Version: "v1", Optional: true},
 					}},
 				}.Detect(config)
-				if err != lifecycle.ErrFail {
+				if err != lifecycle.ErrFailedDetection {
 					t.Fatalf("Unexpected error:\n%s\n", err)
 				}