Renovate doesn't handle single-quoted empty value for Dockerfile's ARG

[gavvvr]

How are you running Renovate?

Self-hosted Renovate CLI

Which platform you running Renovate on?

GitHub.com

Which version of Renovate are you using?

43.197.0

Please tell us more about your question or problem

Consider the following Dockerfile in the repo:

ARG DOCKER_HUB_MIRROR=''
ARG NODE_VERSION=21
FROM ${DOCKER_HUB_MIRROR}node:${NODE_VERSION}-alpine
RUN apk upgrade --no-cache

I know, that most examples at docker.com use double-quotes, but single-quotes here are also valid and docker builds the image with no errors or warnings.

Meanwhile Renovate will fail with:

Failed to look up docker package ''node: no-result

as if '' was the value of DOCKER_HUB_MIRROR.

Logs (if relevant)

Logs

 INFO: Docker Hub lookup failure (repository=gavvvr/repros, baseBranch=renovate-issues)
       "err": {"message": "page-not-found"}
       Error: page-not-found
           at getAuthHeaders (file:///usr/local/renovate/lib/modules/datasource/docker/common.ts:77:13)
           at processTicksAndRejections (node:internal/process/task_queues:104:5)
           at DockerDatasource.getDockerApiTags (file:///usr/local/renovate/lib/modules/datasource/docker/index.ts:695:21)
           at DockerDatasource._getTags (file:///usr/local/renovate/lib/modules/datasource/docker/index.ts:789:16)
           at withCache (file:///usr/local/renovate/lib/util/cache/package/with-cache.ts:126:18)
           at DockerDatasource._getReleases (file:///usr/local/renovate/lib/modules/datasource/docker/index.ts:1172:36)
           at withCache (file:///usr/local/renovate/lib/util/cache/package/with-cache.ts:126:18)
           at getRegistryReleases (file:///usr/local/renovate/lib/modules/datasource/index.ts:96:15)
           at fetchReleases (file:///usr/local/renovate/lib/modules/datasource/index.ts:385:15)
           at lookupUpdates (file:///usr/local/renovate/lib/workers/repository/process/lookup/index.ts:159:56)
           at file:///usr/local/renovate/lib/workers/repository/process/fetch.ts:81:12
           at LookupStats.wrap (file:///usr/local/renovate/lib/util/stats.ts:39:20)
           at file:///usr/local/renovate/lib/workers/repository/process/fetch.ts:141:14
           at file:///usr/local/renovate/node_modules/.pnpm/p-map@6.0.0/node_modules/p-map/index.js:139:20

WARN: Package lookup failures (repository=gavvvr/repros)
      "warnings": ["Failed to look up docker package ''node: no-result"],
      "files": ["Dockerfile"]

Here is the repo: https://github.com/gavvvr/repros/tree/renovate-43631
and CI logs: https://github.com/gavvvr/repros/actions/runs/26522833187/job/78118379664#step:3:118

[gavvvr]

@mg1986jp Yeah, this looks like a Renovate parser bug.

I was about to report the bug to Renovate, but the Issues template redirected me to Discussions instead.
The discussion I started already looks like a bug report, so if GitHub can convert a discussion into an issue, let's do that.

[jamietanna]

Sorry, this user is spamming the Discussions with AI generated replies. I've blocked them now

@RahulGautamSingh mind taking a look at this question?

[RahulGautamSingh]

Issue Created: #44497

PR welcome