[FR] allow setting bazel-version explicitly

[betaboon]

Currently bazel.yaml set's two bazel-versions "implicitly", the version from .bazelversion and 8.0.0rc1. (source)

It would be great to be able to set the bazel-versions explicitly.

maybe something like this:

jobs:
  test:
    uses: bazel-contrib/.github/.github/workflows/bazel.yaml@v6
    with:
      bazelversions: |
        [
          "6.5.0",
          "7.4.1",
          "8.0.0rc1"
        ]

which could lead to the list being .bazelversion+those versions.

[betaboon]

I've been trying with the following patch.
would you be open for a PR like this?

diff --git a/.github/workflows/bazel.yaml b/.github/workflows/bazel.yaml
index b68669d..b3715ab 100644
--- a/.github/workflows/bazel.yaml
+++ b/.github/workflows/bazel.yaml
@@ -21,6 +21,15 @@ on:
           JSON-formatted array of folders to run 'bazel test' in.
           For example, '[".", "e2e/smoke"]'
         type: string
+      bazelversions:
+        description: |
+          JSON-formatted array of bazelversion to run 'bazel test' for.
+
+          If this option is not set, the version from .bazelversion is used.
+
+          For example, '["7.4.1", "8.0.0rc1"]'
+        type: string
+        default: "[]"
       exclude:
         description: |
           JSON-formatted array of exclusions to the generated matrix of tests.
@@ -85,11 +94,10 @@ jobs:
       - uses: actions/checkout@v4
       # NB: we assume this is Bazel 7
       - id: bazel_from_bazelversion
+        if: inputs.bazelversions == '[]'
         run: echo "bazelversion=$(head -n 1 .bazelversion)" >> $GITHUB_OUTPUT
-      - id: bazel_8
-        run: echo "bazelversion=8.0.0rc1" >> $GITHUB_OUTPUT
     outputs:
-      # Will look like ["<version from .bazelversion>", "x.y.z"]
+      # Will look like ["<version from .bazelversion>"]
       bazelversions: ${{ toJSON(steps.*.outputs.bazelversion) }}
 
   test:
@@ -105,7 +113,11 @@ jobs:
       fail-fast: false
       matrix:
         os: ${{ fromJSON(needs.matrix-prep-os.outputs.os) }}
-        bazelversion: ${{ fromJSON(needs.matrix-prep-bazelversion.outputs.bazelversions) }}
+        bazelversion:
+          [
+            "${{ fromJSON(needs.matrix-prep-bazelversion.outputs.bazelversions) }}",
+            "${{ fromJSON(inputs.bazelversions) }}",
+          ]
         folder: ${{ fromJSON(inputs.folders) }}
         bzlmodEnabled: [true, false]
         exclude: ${{ fromJSON(inputs.exclude) }}

[betaboon]

just to be explicit: I'd be willing to send a PR for this as long as this is a welcome change.

[alexeagle]

Yes I think we should improve this. I myself tripped over it last week, when updating the .bazelversion in a project to 8.0.0.

I'd be a bit concerned about wasted time/resources if bazelrc and the workflow use different versions of a major, like .bazelversion has 8.0.1 while ci.yaml workflow has 8.0.0 - the user didn't mean to test both of those.

https://github.com/bazel-contrib/bazel-lib/blob/b2d88f07223ff097a13e4851ccca455f3b430d10/.github/workflows/ci.yaml#L25-L35 is a much more complex setup. It makes my eyes bleed even though I love bash. However it does solve for that issue and it's worth studying.

[betaboon]

just to verify i understand:
assuming we allow declaring the tested bazelversions in the workflow, as described above, you're suggesting that the version from .bazelversion should overwrite the same major-version declared in the workflow?

if that's the case i see one downside tho:
if there are excludes in the workflow, that match one of the bazelversions declared in the workflow, they wouldn't apply anymore.
or we would need to do the same .bazelversion-overwrites-major-in-workflow thing.

also that assumes that testing for multiple minor- or patch-versions is not a usecase, which it might not be.