Stabilize helmfile-diff output (#1619)

`helmfile-diff` sorts multiple and concurrent helm-diff outputs and stabilizes writes to stdout.

It's required to use the stdout from helmfile-diff to detect if there was another change(s) between 2 points in time.

For example, terraform-provider-helmfile runs a helmfile-diff on `terraform plan` and another on `terraform apply`. `terraform`, by design, fails when helmfile-diff outputs were not equivalent. Stabilized helmfile-diff output rescues that.

pkg/helmexec/context.go

@@ -1,6 +1,7 @@
 package helmexec
 
 import (
+	"io"
 	"os"
 	"path/filepath"
 )
@@ -10,6 +11,7 @@ type HelmContext struct {
 	TillerNamespace string
 	HistoryMax      int
 	WorkerIndex     int
+	Writer          io.Writer
 }
 
 func (context *HelmContext) GetTillerlessArgs(helm *execer) []string {

pkg/helmexec/exec.go

@@ -183,7 +183,7 @@ func (helm *execer) SyncRelease(context HelmContext, name, chart string, flags .
 	}
 
 	out, err := helm.exec(append(append(preArgs, "upgrade", "--install", "--reset-values", name, chart), flags...), env)
-	helm.write(out)
+	helm.write(nil, out)
 	return err
 }
 
@@ -192,7 +192,7 @@ func (helm *execer) ReleaseStatus(context HelmContext, name string, flags ...str
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
 	out, err := helm.exec(append(append(preArgs, "status", name), flags...), env)
-	helm.write(out)
+	helm.write(nil, out)
 	return err
 }
 
@@ -219,7 +219,7 @@ func (helm *execer) List(context HelmContext, filter string, flags ...string) (s
 		lines = lines[1:]
 		out = []byte(strings.Join(lines, "\n"))
 	}
-	helm.write(out)
+	helm.write(nil, out)
 	return string(out), err
 }
 
@@ -317,12 +317,16 @@ func (helm *execer) TemplateRelease(name string, chart string, flags ...string)
 	}
 
 	out, err := helm.exec(append(args, flags...), map[string]string{})
-	helm.write(out)
+	helm.write(nil, out)
 	return err
 }
 
 func (helm *execer) DiffRelease(context HelmContext, name, chart string, suppressDiff bool, flags ...string) error {
-	helm.logger.Infof("Comparing release=%v, chart=%v", name, chart)
+	if context.Writer != nil {
+		fmt.Fprintf(context.Writer, "Comparing release=%v, chart=%v\n", name, chart)
+	} else {
+		helm.logger.Infof("Comparing release=%v, chart=%v", name, chart)
+	}
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
 	out, err := helm.exec(append(append(preArgs, "diff", "upgrade", "--reset-values", "--allow-unreleased", name, chart), flags...), env)
@@ -340,13 +344,13 @@ func (helm *execer) DiffRelease(context HelmContext, name, chart string, suppres
 		case ExitError:
 			if e.ExitStatus() == 2 {
 				if !(suppressDiff) {
-					helm.write(out)
+					helm.write(context.Writer, out)
 				}
 				return err
 			}
 		}
 	} else if !(suppressDiff) {
-		helm.write(out)
+		helm.write(context.Writer, out)
 	}
 	return err
 }
@@ -354,7 +358,7 @@ func (helm *execer) DiffRelease(context HelmContext, name, chart string, suppres
 func (helm *execer) Lint(name, chart string, flags ...string) error {
 	helm.logger.Infof("Linting release=%v, chart=%v", name, chart)
 	out, err := helm.exec(append([]string{"lint", chart}, flags...), map[string]string{})
-	helm.write(out)
+	helm.write(nil, out)
 	return err
 }
 
@@ -370,7 +374,7 @@ func (helm *execer) DeleteRelease(context HelmContext, name string, flags ...str
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
 	out, err := helm.exec(append(append(preArgs, "delete", name), flags...), env)
-	helm.write(out)
+	helm.write(nil, out)
 	return err
 }
 
@@ -380,7 +384,7 @@ func (helm *execer) TestRelease(context HelmContext, name string, flags ...strin
 	env := context.getTillerlessEnv()
 	args := []string{"test", name}
 	out, err := helm.exec(append(append(preArgs, args...), flags...), env)
-	helm.write(out)
+	helm.write(nil, out)
 	return err
 }
 
@@ -413,9 +417,12 @@ func (helm *execer) info(out []byte) {
 	}
 }
 
-func (helm *execer) write(out []byte) {
+func (helm *execer) write(w io.Writer, out []byte) {
 	if len(out) > 0 {
-		fmt.Printf("%s\n", out)
+		if w == nil {
+			w = os.Stdout
+		}
+		fmt.Fprintf(w, "%s\n", out)
 	}
 }
 

pkg/state/state.go

@@ -1418,7 +1418,9 @@ func (st *HelmState) LintReleases(helm helmexec.Interface, additionalValues []st
 }
 
 type diffResult struct {
-	err *ReleaseError
+	release *ReleaseSpec
+	err     *ReleaseError
+	buf     *bytes.Buffer
 }
 
 type diffPrepareResult struct {
@@ -1600,6 +1602,14 @@ func (st *HelmState) createHelmContext(spec *ReleaseSpec, workerIndex int) helme
 	}
 }
 
+func (st *HelmState) createHelmContextWithWriter(spec *ReleaseSpec, w io.Writer) helmexec.HelmContext {
+	ctx := st.createHelmContext(spec, 0)
+
+	ctx.Writer = w
+
+	return ctx
+}
+
 type DiffOpts struct {
 	Context int
 	NoColor bool
@@ -1617,7 +1627,13 @@ func (o *DiffOpts) Apply(opts *DiffOpts) {
 type DiffOpt interface{ Apply(*DiffOpts) }
 
 // DiffReleases wrapper for executing helm diff on the releases
-// It returns releases that had any changes
+// It returns releases that had any changes, and errors if any.
+//
+// This function has responsibility to stabilize the order of writes to stdout from multiple concurrent helm-diff runs.
+// It's required to use the stdout from helmfile-diff to detect if there was another change(s) between 2 points in time.
+// For example, terraform-provider-helmfile runs a helmfile-diff on `terraform plan` and another on `terraform apply`.
+// `terraform`, by design, fails when helmfile-diff outputs were not equivalent.
+// Stabilized helmfile-diff output rescues that.
 func (st *HelmState) DiffReleases(helm helmexec.Interface, additionalValues []string, workerLimit int, detailedExitCode, includeTests, suppressSecrets, suppressDiff, triggerCleanupEvents bool, opt ...DiffOpt) ([]ReleaseSpec, []error) {
 	opts := &DiffOpts{}
 	for _, o := range opt {
@@ -1644,6 +1660,7 @@ func (st *HelmState) DiffReleases(helm helmexec.Interface, additionalValues []st
 	results := make(chan diffResult, len(preps))
 
 	rs := []ReleaseSpec{}
+	outputs := map[string]*bytes.Buffer{}
 	errs := []error{}
 
 	// The exit code returned by helm-diff when it detected any changes
@@ -1662,19 +1679,20 @@ func (st *HelmState) DiffReleases(helm helmexec.Interface, additionalValues []st
 			for prep := range jobQueue {
 				flags := prep.flags
 				release := prep.release
+				buf := &bytes.Buffer{}
 				if prep.upgradeDueToSkippedDiff {
-					results <- diffResult{&ReleaseError{ReleaseSpec: release, err: nil, Code: HelmDiffExitCodeChanged}}
+					results <- diffResult{release, &ReleaseError{ReleaseSpec: release, err: nil, Code: HelmDiffExitCodeChanged}, buf}
-				} else if err := helm.DiffRelease(st.createHelmContext(release, workerIndex), release.Name, normalizeChart(st.basePath, release.Chart), suppressDiff, flags...); err != nil {
+				} else if err := helm.DiffRelease(st.createHelmContextWithWriter(release, buf), release.Name, normalizeChart(st.basePath, release.Chart), suppressDiff, flags...); err != nil {
 					switch e := err.(type) {
 					case helmexec.ExitError:
 						// Propagate any non-zero exit status from the external command like `helm` that is failed under the hood
-						results <- diffResult{&ReleaseError{release, err, e.ExitStatus()}}
+						results <- diffResult{release, &ReleaseError{release, err, e.ExitStatus()}, buf}
 					default:
-						results <- diffResult{&ReleaseError{release, err, 0}}
+						results <- diffResult{release, &ReleaseError{release, err, 0}, buf}
 					}
 				} else {
 					// diff succeeded, found no changes
-					results <- diffResult{}
+					results <- diffResult{release, nil, buf}
 				}
 
 				if triggerCleanupEvents {
@@ -1693,10 +1711,18 @@ func (st *HelmState) DiffReleases(helm helmexec.Interface, additionalValues []st
 						rs = append(rs, *res.err.ReleaseSpec)
 					}
 				}
+
+				outputs[ReleaseToID(res.release)] = res.buf
 			}
 		},
 	)
 
+	for _, p := range preps {
+		if stdout, ok := outputs[ReleaseToID(p.release)]; ok {
+			fmt.Print(stdout.String())
+		}
+	}
+
 	return rs, errs
 }