feat: add --write-output flag to helmfile fetch for air-gapped environments by yxxhero · Pull Request #2572 · helmfile/helmfile

yxxhero · 2026-05-02T09:11:33Z

Summary

Add --write-output flag to helmfile fetch that outputs a modified helmfile.yaml with chart references updated to point to downloaded local chart paths
Combined with --output-dir, this enables preparing all charts for deployment in air-gapped environments
Adds unit test for flag validation and integration test for the full fetch-with-write-output flow

Usage

# Download all charts and output modified helmfile.yaml
helmfile fetch --output-dir ./charts --write-output > helmfile-airgapped.yaml

# Transfer ./charts/ and helmfile-airgapped.yaml to air-gapped environment
# Deploy with:
helmfile -f helmfile-airgapped.yaml --skip-deps sync

Changes

pkg/config/fetch.go — Added WriteOutput field and accessor
pkg/app/config.go — Added WriteOutput() to FetchConfigProvider interface
pkg/app/app.go — Enhanced App.Fetch() to output modified helmfile.yaml when --write-output is set
cmd/fetch.go — Added --write-output flag and improved command description
pkg/app/app_test.go — Added unit tests
test/integration/test-cases/fetch-write-output.sh — New integration test
test/integration/test-cases/fetch-write-output/input/helmfile.yaml.gotmpl — Test input
test/integration/run.sh — Registered new test case

Fixes #2571

…nments Add --write-output flag to helmfile fetch that outputs a modified helmfile.yaml with chart references updated to point to downloaded local chart paths. Combined with --output-dir, this enables preparing all charts for deployment in air-gapped environments. Usage: helmfile fetch --output-dir ./charts --write-output > helmfile-airgapped.yaml Fixes #2571 Signed-off-by: yxxhero <[email protected]> Signed-off-by: yxxhero <[email protected]>

yxxhero · 2026-05-02T09:37:50Z

@copilot fix ci issue.

…st item chart field Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/d00f71ab-d40d-4220-9b11-97674597685f Co-authored-by: yxxhero <[email protected]>

Copilot · 2026-05-02T09:52:32Z

@copilot fix ci issue.

Fixed in commit f212179. The CI failure was caused by the integration test's grep pattern ^ *chart: not matching YAML list items ( - chart: /path). Instead, it was matching labels.chart: raw (a Helmfile auto-generated label). Updated the pattern to ^\s+(-\s+)?chart: which correctly matches both list-item and nested-key YAML forms, so head -1 now returns the release's actual chart path.

Copilot

Pull request overview

Adds an option to make helmfile fetch usable for air-gapped workflows by emitting a modified Helmfile with chart references rewritten to the locally fetched chart paths.

Changes:

Add --write-output flag plumbed through config/provider interfaces.
Update App.Fetch() to (optionally) rewrite release chart fields to the fetched local chart paths and print the resulting YAML to stdout.
Add unit + integration coverage for the new flag and end-to-end behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`cmd/fetch.go`	Adds the `--write-output` CLI flag and expands command help text.
`pkg/config/fetch.go`	Extends fetch options/config with `WriteOutput` and accessor.
`pkg/app/config.go`	Extends `FetchConfigProvider` interface with `WriteOutput()`.
`pkg/app/app.go`	Implements write-output behavior in `App.Fetch()` and enforces `--output-dir` requirement.
`pkg/app/app_test.go`	Adds a unit test validating `--write-output` requires `--output-dir`.
`test/integration/test-cases/fetch-write-output.sh`	New integration test exercising fetch + write-output end-to-end.
`test/integration/test-cases/fetch-write-output/input/helmfile.yaml.gotmpl`	Integration test input Helmfile.
`test/integration/run.sh`	Registers the new integration test case.

+	if c.WriteOutput() && c.OutputDir() == "" {
+		return fmt.Errorf("--output-dir is required when --write-output is set")
+	}
+


@@ -403,6 +407,27 @@ func (a *App) Fetch(c FetchConfigProvider) error {
 			OutputDirTemplate: c.OutputDirTemplate(),
 			Concurrency:       c.Concurrency(),
 		}, func() []error {


yxxhero · 2026-05-02T10:35:50Z

@copilot fix comments.

… in --write-output mode Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/d338e24c-4f6f-4a59-a319-4b975e0efdcb Co-authored-by: yxxhero <[email protected]>

Copilot · 2026-05-02T10:45:12Z

@copilot fix comments.

Fixed in commit bd9fcf1:

Stdout corruption (run.go): Changed fmt.Printf("Charts will be downloaded to: ...") → fmt.Fprintf(os.Stderr, ...) so the status message goes to stderr and never appears in the YAML output written to stdout.
Concurrent interleaving (app.go): Added a.SequentialHelmfiles = true in Fetch() when WriteOutput() is true, forcing sequential state-file processing so YAML documents are never interleaved.

Integration test updated to capture stdout only (2>/dev/null) and assert the status message is absent from stdout.

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

+		// without interleaving when multiple helmfile state files are processed.
+		a.SequentialHelmfiles = true


+
+				sourceFile, err := run.state.FullFilePath()
+				if err != nil {
+					return []error{err}
+				}
+				fmt.Printf("---\n#  Source: %s\n\n%+v", sourceFile, stateYaml)


yxxhero · 2026-05-02T10:51:36Z

@copilot fix comments.

…ng formatting Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/cfa9f3f4-c72f-4760-9c51-88bc6f30add2 Co-authored-by: yxxhero <[email protected]>

…te-output Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/cfa9f3f4-c72f-4760-9c51-88bc6f30add2 Co-authored-by: yxxhero <[email protected]>

Copilot · 2026-05-02T11:04:29Z

@copilot fix comments.

Fixed in commit 39da580:

SequentialHelmfiles mutation (app.go): Now saved and restored via defer so the App instance is not permanently affected after Fetch returns.
%+v → %s (app.go): stateYaml is now printed with %s for explicit, predictable string formatting.
Test (app_test.go): Added TestFetch_WriteOutputRestoresSequentialHelmfiles which uses mockHelmExec to exercise the actual defer path — it verifies that SequentialHelmfiles (starting as false) is restored to false after a full Fetch run with --write-output.

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

+cat ${fetch_write_output_tmp}/helmfile-tests/local-chart/raw/latest/Chart.yaml || fail "Chart.yaml should exist in fetched output directory"
+
+info "Verifying the chart path in output matches the actual downloaded location"
+chart_path=$(echo "${output}" | grep -E "^\s+(-\s+)?chart:" | head -1 | sed 's/.*chart: *//' | tr -d '"')


+test_start "$case_title"
+
+info "Testing helmfile fetch --write-output with local chart"
+output=$(${helmfile} -f ${fetch_write_output_input_dir}/helmfile.yaml.gotmpl fetch --output-dir ${fetch_write_output_tmp} --write-output 2>/dev/null) \


+    fail "chart path '${chart_path}' from output should point to a directory containing Chart.yaml"
+fi
+
+rm -rf ${fetch_write_output_tmp}


Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

+	if c.WriteOutput() {
+		// Force sequential processing to ensure YAML documents are emitted in order
+		// without interleaving when multiple helmfile state files are processed.
+		// Restore the original value when Fetch returns so the App instance is not
+		// permanently mutated (important for tests and library usage).
+		prev := a.SequentialHelmfiles
+		a.SequentialHelmfiles = true
+		defer func() { a.SequentialHelmfiles = prev }()
+	}


yxxhero · 2026-05-02T23:11:11Z

@copilot fix comments.

…ear error Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/f608a0d0-7f52-4e3f-9fac-ab966bd01efb Co-authored-by: yxxhero <[email protected]>

Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/f608a0d0-7f52-4e3f-9fac-ab966bd01efb Co-authored-by: yxxhero <[email protected]>

Copilot · 2026-05-02T23:21:22Z

@copilot fix comments.

Fixed in commit 9de91ac. Added a processedStateFileCount closure variable in Fetch() that increments on each ForEachState callback invocation. When --write-output is set and the count exceeds 1, the callback immediately returns a clear error:

--write-output requires a single helmfile state file, but multiple were found; use -f to specify a single helmfile instead of a directory or a helmfile with nested helmfiles: entries

This prevents silently emitting a multi-document YAML stream whose documents would be merged in semantics-altering ways when fed back to helmfile -f. The SequentialHelmfiles = true setting ensures the error fires on the exact second file rather than some arbitrary concurrency-dependent invocation. A new test TestFetch_WriteOutput_ErrorsOnMultipleStateFiles covers this path using a helmfile.d/ directory with two state files.

yxxhero · 2026-05-02T23:32:36Z

@copilot fix ci issue.

…et lint error Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/4b060131-a977-44b0-98f7-42bc108ae8e8 Co-authored-by: yxxhero <[email protected]>

Copilot · 2026-05-02T23:40:29Z

@copilot fix ci issue.

Fixed in commit 92b649e. The lint failure was a nakedret violation: the anonymous callback in Fetch was 56 lines (exceeds the max-func-lines: 50 threshold), and the bare return at the end triggered the linter. Changed it to return ok, errs to make the return explicit.

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

+				if err != nil {
+					return []error{err}
+				}
+				fmt.Printf("---\n#  Source: %s\n\n%s", sourceFile, stateYaml)
+			}


 	f.IntVar(&fetchOptions.Concurrency, "concurrency", 0, "maximum number of concurrent helm processes to run, 0 is unlimited")
 	f.StringVar(&fetchOptions.OutputDir, "output-dir", "", "directory to store charts (default: temporary directory which is deleted when the command terminates)")
 	f.StringVar(&fetchOptions.OutputDirTemplate, "output-dir-template", state.DefaultFetchOutputDirTemplate, "go text template for generating the output directory. Available fields: {{ .OutputDir }}, {{ .ChartName }}, {{ .Release.* }}, {{ .Environment.Name }}, {{ .Environment.KubeContext }}, {{ .Environment.Values.* }}")
+	f.BoolVar(&fetchOptions.WriteOutput, "write-output", false, "write a helmfile.yaml to stdout with chart references updated to point to the downloaded local chart paths. Requires --output-dir.")


yxxhero · 2026-05-03T01:41:39Z

@copilot fix comments

Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/50c6ad2e-125c-43c1-b9c3-37fe1686a8eb Co-authored-by: yxxhero <[email protected]>

Copilot · 2026-05-03T01:51:21Z

@copilot fix comments

Fixed in commits e341afa and c424589:

Buffered YAML output (app.go): Replaced direct fmt.Printf inside the ForEachState callback with writes to a strings.Builder. The buffer is only flushed to stdout after ForEachState returns without error, so partial/corrupted YAML never reaches stdout on failure.
Flag description (cmd/fetch.go): Shortened the --write-output flag help to a concise one-liner. The single-file limitation and the -f guidance are now in the command's Long help text instead.

yxxhero · 2026-05-03T08:53:20Z

@copilot review 代码确保符合预期

Copilot · 2026-05-03T08:58:58Z

@copilot review 代码确保符合预期

Code review confirms all changes meet expectations:

pkg/app/app.go: SequentialHelmfiles and helm.SetEnableLiveOutput are both mutated temporarily and restored via defer; YAML is buffered in strings.Builder and only flushed to stdout after ForEachState succeeds (no partial output on failure); multi-file inputs produce a clear error on the second state file.
cmd/fetch.go: --write-output flag has a concise one-liner description; the single-state-file limitation is documented in the Long help text.
pkg/app/run.go: Charts will be downloaded to: goes to stderr.
pkg/app/app_test.go: Three unit tests covering validation, multi-file error, and the defer-restore path (with enableLiveOutput starting true so removing the defer causes a test failure).
Integration test: POSIX-portable [[:space:]] in grep, proper quoting for all path variables.

All TestFetch_WriteOutput* unit tests pass (ok github.com/helmfile/helmfile/pkg/app 1.096s) and go build ./... succeeds.

@copilot review 代码确保符合预期

Code review complete — everything is correct and tests pass.

Key properties verified:

SequentialHelmfiles and helm.enableLiveOutput are both saved/restored via defer (unit test TestFetch_WriteOutputRestoresSequentialHelmfiles would fail without either defer)
YAML is buffered in strings.Builder and only written to stdout after ForEachState returns nil — no partial output on failure
Multi-file input detected on the 2nd callback invocation and returns an error before any YAML reaches stdout
Status messages go to stderr; live output disabled during callback
--write-output flag description and Long help both document the --output-dir requirement and single-file limitation
Integration test uses POSIX-portable [[:space:]] and quoted variables throughout

yxxhero requested review from aditmeno, itscaro, mumoshu, xiaomudk and zhaque44 as code owners May 2, 2026 09:11

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refactor: apply code review suggestions for variable and test naming

28900d1

Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/f608a0d0-7f52-4e3f-9fac-ab966bd01efb Co-authored-by: yxxhero <[email protected]>

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fix: buffer YAML output and update --write-output flag description

e341afa

Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/50c6ad2e-125c-43c1-b9c3-37fe1686a8eb Co-authored-by: yxxhero <[email protected]>

fix: shorten --write-output flag description, move detail to Long help

c424589

Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/50c6ad2e-125c-43c1-b9c3-37fe1686a8eb Co-authored-by: yxxhero <[email protected]>

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yxxhero merged commit 08a2277 into main May 3, 2026
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yxxhero deleted the feat/fetch-write-output-airgapped branch May 3, 2026 10:32

		// without interleaving when multiple helmfile state files are processed.
		a.SequentialHelmfiles = true

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yxxhero commented May 2, 2026

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