Chore: [AEA-0000] - get tag from dockerfile if not in devcontainer.json

[anthony-nhs]

Summary

• Routine Change

Details

• get tag from dockerfile if not in devcontainer.json

[github-actions]

This PR is linked to a ticket in an NHS Digital JIRA Project. Here's a handy link to the ticket:

AEA-0000

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

This PR updates the repo-config GitHub workflow to derive the devcontainer image tag from the .devcontainer/Dockerfile when it isn’t present in .devcontainer/devcontainer.json, and aligns the devcontainer files toward using the Dockerfile as the source of truth.

Changes:

• Remove IMAGE_NAME / IMAGE_VERSION build args from .devcontainer/devcontainer.json.
• Pin the devcontainer base image reference directly in .devcontainer/Dockerfile.
• Add a fallback in .github/workflows/get-repo-config.yml to parse the FROM ... reference in the Dockerfile when the JSON args are missing.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
.github/workflows/get-repo-config.yml	Adds Dockerfile parsing fallback for devcontainer image/version discovery.
.devcontainer/Dockerfile	Pins the base image reference (name + tag) directly in FROM.
.devcontainer/devcontainer.json	Removes image/version args that were previously used as the workflow’s source of truth.

[Copilot]

This workflow can now source devcontainer_image/devcontainer_version from the Dockerfile rather than devcontainer.json; please update the workflow output descriptions/comments accordingly to avoid misleading callers.

[Copilot]

Removing IMAGE_NAME/IMAGE_VERSION from devcontainer.json will break workflows/scripts that read these fields (e.g. .github/workflows/update-dev-container-version.yml reads .build.args.IMAGE_NAME and .build.args.IMAGE_VERSION). Either keep these args in devcontainer.json, or update the version-bump workflow(s) to derive and update the Dockerfile FROM tag instead.

[Copilot]

Add set -euo pipefail at the start of this step (and fail if the Dockerfile/ FROM line can't be read) so jq/awk failures don't silently produce empty/incorrect outputs.

Suggested change

	TAG_FORMAT=$(yq '.TAG_FORMAT' .github/config/settings.yml)
	DEVCONTAINER_IMAGE=$(jq -r '.build.args.IMAGE_NAME' .devcontainer/devcontainer.json)
	DEVCONTAINER_VERSION=$(jq -r '.build.args.IMAGE_VERSION' .devcontainer/devcontainer.json)
	if [ "$DEVCONTAINER_IMAGE" == "null" ]; then
	dockerfile=".devcontainer/Dockerfile"
	from_ref="$(
	awk '/^FROM[[:space:]]+/ { print $2; exit }' "$dockerfile"
	)"
	set -euo pipefail
	TAG_FORMAT=$(yq '.TAG_FORMAT' .github/config/settings.yml)
	DEVCONTAINER_IMAGE=$(jq -r '.build.args.IMAGE_NAME' .devcontainer/devcontainer.json)
	DEVCONTAINER_VERSION=$(jq -r '.build.args.IMAGE_VERSION' .devcontainer/devcontainer.json)
	if [ "$DEVCONTAINER_IMAGE" = "null" ]; then
	dockerfile=".devcontainer/Dockerfile"
	if [ ! -f "$dockerfile" ]; then
	echo "Error: Dockerfile '$dockerfile' not found; cannot derive DEVCONTAINER_IMAGE/DEVCONTAINER_VERSION." >&2
	exit 1
	fi
	from_ref="$(
	awk '/^FROM[[:space:]]+/ { print $2; exit }' "$dockerfile"
	)"
	if [ -z "$from_ref" ]; then
	echo "Error: No FROM line found in '$dockerfile'; cannot derive DEVCONTAINER_IMAGE/DEVCONTAINER_VERSION." >&2
	exit 1
	fi

[Copilot]

The fallback only checks DEVCONTAINER_IMAGE for "null". If IMAGE_NAME is present but IMAGE_VERSION is missing/"null" (or either value is empty), later steps will build an invalid RUNTIME_DOCKER_IMAGE. Consider checking both DEVCONTAINER_IMAGE and DEVCONTAINER_VERSION (and empty-string) before deciding whether to parse the Dockerfile.

Suggested change

	if [ "$DEVCONTAINER_IMAGE" == "null" ]; then
	if [ -z "$DEVCONTAINER_IMAGE" ] || [ "$DEVCONTAINER_IMAGE" = "null" ] || [ -z "$DEVCONTAINER_VERSION" ] || [ "$DEVCONTAINER_VERSION" = "null" ]; then

[Copilot]

The fallback hard-codes .devcontainer/Dockerfile, but devcontainer.json already declares the dockerfile path (.build.dockerfile). For a reusable workflow this can break repos that use a different filename; consider reading .build.dockerfile from devcontainer.json and constructing the path from that value.

Suggested change

	dockerfile=".devcontainer/Dockerfile"
	dockerfile_name=$(jq -r '.build.dockerfile // "Dockerfile"' .devcontainer/devcontainer.json)
	dockerfile=".devcontainer/${dockerfile_name}"

[Copilot]

Docs now appear out of date: README.md ("Update Dev Container Version" section) states devcontainer.json must include build.args.IMAGE_NAME and build.args.IMAGE_VERSION, but this PR removes them. Please update the documentation (and/or the update-dev-container-version workflow) to match the new source of truth (Dockerfile).