argocd-source-lint

Static linter for detecting silent failures in multi-source ArgoCD Application resources.

It catches cases that are easy to miss because ArgoCD may still report an Application as healthy and synced: manifests that are never referenced, broken $values references, missing ignoreDifferences, invalid targets, conflicting Applications, and similar configuration issues.

argocd-source-lint works from the Git checkout already available in CI. It doesn't connect to the Kubernetes cluster and does not require a kubeconfig or cluster credentials.

Contents

• What the tool does
• How it works
• Limitations
• Installation
• Usage
• Configuration
• Using it on an existing repository
• CI/CD integration
• Development
• Changelog
• Security policy
• License

What the tool does

Rule	Default severity	Detects
orphan-source	error	A manifest present in the repository but not covered by any declared source
broken-values-ref	error	A Helm valueFiles entry, including $ref, that points to a file that doesn't exist
missing-ignore-diff	warning	A known at-risk CRD with selfHeal: true but no matching ignoreDifferences configuration
phantom-target	error	A targetRevision or path that resolves to nothing in the repository
unresolvable-generator	info	An ApplicationSet generator that can't be resolved from the local checkout alone
double-coverage	error	A file covered by more than one different Application, with each Application syncing it independently
revision-mismatch	info	A source whose targetRevision differs from the checked-out revision
project-scope-violation	error	An Application source or destination outside the sourceRepos or destinations allowed by its AppProject
hpa-selfheal-conflict	warning	An HPA and ArgoCD selfHeal both managing spec.replicas without the required ignore configuration
sync-validation-disabled	info	The Validate=false sync option, which allows an invalid manifest to be applied
duplicate-application-name	error	Two or more Applications using the same namespace and name
malformed-ignore-diff-pointer	warning	An ignoreDifferences.jsonPointers entry that doesn't start with / as required by RFC 6901
malformed-ignore-diff-jq-expression	warning	An ignoreDifferences.jqPathExpressions entry that doesn't start with . and fails to compile as jq
unknown-sync-option	warning	An unknown or incorrectly cased ArgoCD sync option
unknown-resource-hook	warning	An unknown ArgoCD hook or hook deletion policy value
malformed-sync-wave	warning	A sync-wave annotation whose value isn't a valid integer

A few examples

duplicate-application-name catches two Applications using the same namespace and name. ArgoCD identifies an Application by that pair, so duplicates can end up competing for the same object.

With hpa-selfheal-conflict, the problem is spec.replicas. If an HPA owns it while ArgoCD self-heal is enabled, ArgoCD can keep restoring the configured replica count. The rule checks for both ignoreDifferences and the RespectIgnoreDifferences sync option.

A malformed JSON pointer is easier to miss than it looks. Entries under ignoreDifferences.jsonPointers have to start with /.

malformed-ignore-diff-jq-expression checks the other form of ignore rule. A malformed jq expression can invalidate the ignoreDifferences configuration for that Application.

Sync options are case-sensitive. Something that looks close enough can still be ignored by ArgoCD, which is what unknown-sync-option looks for.

For sync waves, the annotation value has to be an integer. An invalid value falls back to wave 0.

Sample run using the default table output:

$ argocd-source-lint .

Rule                 Severity  File                                 Application       Message
────────────────────────────────────────────────────────────────────────────────────────────────
phantom-target       error     apps/payments/application.yaml       payments-service  targetRevision "release-3.2"
                                                                                     does not resolve to any
                                                                                     local ref
orphan-source        error     manifests/legacy/old-ingress.yaml    -                 not covered by any
                                                                                     declared source
double-coverage      error     manifests/shared/configmap.yaml      -                 covered by both "team-a"
                                                                                     and "team-b"
missing-ignore-diff  warning   apps/postgres/application.yaml       postgres-cluster  selfHeal: true with no
                                                                                     ignoreDifferences on a
                                                                                     CNPG Cluster

4 findings (3 error, 1 warning, 0 info) — exit code 1

How it works

flowchart LR
    A["Git repo checkout"] --> B["Discovery<br/>Applications + ApplicationSets"]
    B --> C["Rules<br/>orphan-source, broken-values-ref,<br/>missing-ignore-diff, phantom-target,<br/>unresolvable-generator, double-coverage,<br/>revision-mismatch, project-scope-violation,<br/>hpa-selfheal-conflict, sync-validation-disabled,<br/>duplicate-application-name, malformed-ignore-diff-pointer,<br/>malformed-ignore-diff-jq-expression, unknown-sync-option,<br/>unknown-resource-hook, malformed-sync-wave"]
    C --> D{"Policy<br/>severity overrides + baseline"}
    D --> E["Reporters<br/>table, json, sarif, gitlab-codequality, junit"]

Discovery and rule evaluation only read the filesystem and the local Git repository. There are no network calls and no cluster credentials are required.

That makes the linter suitable for a normal CI job as long as the repository has already been checked out.

Limitations

Kubernetes cluster

The linter works from the repository checkout and doesn't query the Kubernetes cluster. Checks that require live cluster state aren't covered.

Kustomize

Kustomize overlays aren't rendered. If you need to validate the rendered result, run kustomize build or a dedicated Kustomize validation tool separately.

orphan-source does inspect kustomization.yaml, though. It follows local references from:

• resources
• bases
• components
• crds
• patches
• generators

This keeps referenced files in an overlay from being reported as orphans.

Remote Kustomize resources are skipped because they cannot be verified from the local checkout.

See DESIGN.md for more details.

ApplicationSet

The following generators can be resolved locally:

• list
• git with directories
• git with files
• matrix
• merge

Applications produced from them go through the same rules as regular Application resources.

Some generators need information that is not available from a checkout alone. This includes:

• clusters
• scmProvider
• pullRequest
• plugin
• goTemplate: true
• generator-level selector filtering

Those cases are reported as unresolvable-generator.

Multi-repository Applications

If an Application points to another Git repository, the linter cannot inspect that repository from the current checkout.

The source is still detected and reported as info.

Installation

pip install argocd-source-lint

Usage

Run the linter from the root of the repository:

argocd-source-lint .

Available output formats are:

table
json
sarif
gitlab-codequality
junit

For example:

argocd-source-lint . --format sarif --output results.sarif

Exit codes

The command returns:

• 0 when there is no blocking finding
• 1 when at least one blocking finding is present

An error always blocks CI.

An unverifiable result also blocks by default. This can happen when a Git revision can't be resolved locally, for example with an incomplete shallow clone.

You can change that behavior with:

unverifiable_blocks_ci: false

Configuration

Copy .argocd-lint.example.yaml to .argocd-lint.yaml at the root of the repository.

Any setting you leave out keeps its default value.

scan_roots:
  - manifests/
  - infra/

rules:
  orphan-source: error
  broken-values-ref: error
  missing-ignore-diff: warning
  phantom-target: error
  unresolvable-generator: info
  double-coverage: error
  revision-mismatch: info
  project-scope-violation: error
  hpa-selfheal-conflict: warning
  sync-validation-disabled: info
  duplicate-application-name: error
  malformed-ignore-diff-pointer: warning
  malformed-ignore-diff-jq-expression: warning
  unknown-sync-option: warning
  unknown-resource-hook: warning
  malformed-sync-wave: warning

unverifiable_blocks_ci: true

exclude_paths:
  - manifests/legacy/**

# Additional operator signatures.
# These are added to the built-in signatures for:
# CNPG, cert-manager, Elastic ECK, RabbitMQ, Strimzi,
# Zalando Postgres Operator, Keycloak Operator and
# External Secrets Operator.
known_operators:
  - crd_trigger: my-operator.io/MyCRD
    name_from: metadata.name
    expect_ignore_on:
      - kind: Secret
        name_pattern: "{name}-credentials"

Custom known_operators entries extend the built-in operator list. They don't replace it.

Using it on an existing repository

Running the linter for the first time on an established repository may uncover findings you don't want to fix immediately.

For example, there may be a leftover manifest from a decommissioned component or files that are deliberately deployed through another process.

You can record the current state as a baseline:

argocd-source-lint . --write-baseline

This creates:

.argocd-lint-baseline.yaml

Commit the file with the repository. Later runs will still report new findings, while entries already recorded in the baseline are accepted.

The baseline is plain YAML, so it's easy to review or edit when needed.

Running --write-baseline again replaces the existing baseline with the current findings.

CI/CD integration

GitHub Actions

The action publishes its SARIF report through github/codeql-action/upload-sarif.

That upload needs permissions on the calling job:

jobs:
  lint:
    runs-on: ubuntu-latest

    permissions:
      security-events: write
      actions: read
      contents: read

    steps:
      - uses: actions/checkout@v4

      - uses: gillesl-dev/argocd-source-lint@v1.0.2
        with:
          path: .

actions: read and contents: read are needed for private repositories.

GitLab CI

GitLab components have to be hosted on the same GitLab instance as the project using them.

argocd-source-lint is hosted on GitHub. Start by copying templates/lint.yml into a project on your GitLab instance.

You'll also need a README.md at the root of that project for GitLab's component layout.

Then include the component using a tag, branch, or commit SHA:

include:
  - component: $CI_SERVER_FQDN/<your-gitlab-group>/argocd-source-lint/lint@v1.0.2
    inputs:
      scope: manifests/

You don't have to publish the component in the GitLab CI/CD Catalog. A normal include: works without Catalog publication.

pre-commit

repos:
  - repo: https://github.com/gillesl-dev/argocd-source-lint
    rev: v1.0.2
    hooks:
      - id: argocd-source-lint

Development

Install the project and development dependencies:

uv sync --extra dev

Run the linter locally:

uv run argocd-source-lint .

Run the tests:

uv run pytest

To try a version published on TestPyPI:

pip install \
  --index-url https://test.pypi.org/simple/ \
  --extra-index-url https://pypi.org/simple/ \
  argocd-source-lint

For implementation details, see DESIGN.md.

To add a rule or operator signature, see CONTRIBUTING.md.

Version history is available in CHANGELOG.md.

License

MIT. See LICENSE.