Dockerfile file analysis should support Buildkit's `RUN --mount` · GoogleContainerTools/skaffold#6091

2021-06-28T14:41:47.000Z

_(From the [`#skaffold` Slack channel](https://kubernetes.slack.com/archives/CABQMSZA6/p1624662175123800))_ Buildkit supports [`run --mount=type=bind,source=xxx,target=yyy`](https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/syntax.md#run---mounttypebind-the-default-mount-type) which behaves similar to a `COPY xxx yyy`. The `type=bind` can be omitted as this is the default mount type. The doc does say that this is only valid with [dockerfile syntax 1.2 or above](https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/syntax.md#build-mounts-run---mount): > To use this flag set Dockerfile version to at least 1.2 > > `# syntax=docker/dockerfile:1.2` ### Expected behavior Skaffold would detect changes to the source in `xxx` and trigger a rebuild. ### Actual behavior [Skaffold doesn't detect the source changes.](https://kubernetes.slack.com/archives/CABQMSZA6/p1624662175123800) ### Information - Skaffold version: unspecified ### Workaround Insert manual `COPY` statements.

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area/buildbuild/dockerhelp wantedkind/feature-requestpriority/p2

Description

(From the #skaffold Slack channel)

Buildkit supports run --mount=type=bind,source=xxx,target=yyy which behaves similar to a COPY xxx yyy. The type=bind can be omitted as this is the default mount type.

The doc does say that this is only valid with dockerfile syntax 1.2 or above:

To use this flag set Dockerfile version to at least 1.2

# syntax=docker/dockerfile:1.2

Expected behavior

Skaffold would detect changes to the source in xxx and trigger a rebuild.

Actual behavior

Skaffold doesn't detect the source changes.

Information

Skaffold version: unspecified

Workaround

Insert manual COPY statements.

Contributor guide

Tech stack: dockerkubernetesgo
Domain: backenddevopsinfrastructurebuild system
Issue type: feature
Difficulty: 3
Estimated time: 1-2 days
Activity status: stale
Clarity: clear
Prerequisites: Basic knowledge of Dockerfile syntaxUnderstanding of Buildkit RUN mount
Newbie friendliness: 40
Research direction: Investigate how Skaffold currently parses Dockerfiles and tracks file dependencies. Look for code that handles `COPY` instructions and extend it to also recognize `RUN mount=type=bind` instructions. The relevant code is likely in the file change detection logic. Also consider the Dockerfile syntax version requirement (1.2 or above). Examine existing tests and the `pkg/skaffold/docker` directory for parsing logic.