CI - Fix smoketests running twice (#4281)

# Description of Changes

Smoketests were running twice because `tests/foo.rs` automatically gets
turned into a test binary, but we also had a `mod.rs` that listed each
file, so they were getting tested via that as well.

This was first broken in
#4184.

# API and ABI breaking changes

None.

# Expected complexity level and risk

1

# Testing

- [x] CI passes
- [x] If I run `cargo ci smoketests` locally, I still see the CLI tests
running
- [x] If I run `cargo ci smoketests` locally, I do not see a particular
CLI test name appearing more than once (e.g.
`cli_cannot_publish_breaking_change_without_flag`)
- [x] `cargo ci smoketests check-mod-list` passes
- [x] `cargo ci smoketests check-mod-list` fails if I `touch
crates/smoketests/tests/smoketests/foo.rs`

---------

Signed-off-by: Zeke Foppa <196249+bfops@users.noreply.github.com>
Co-authored-by: Zeke Foppa <bfops@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: bfops

.github/workflows/ci.yml

@@ -1187,3 +1187,59 @@ jobs:
           fi
 
           echo "No Python smoketest changes detected."
+
+  smoketests_mod_rs_complete:
+    name: Check smoketests/mod.rs is complete
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    env:
+      CARGO_TARGET_DIR: ${{ github.workspace }}/target
+    steps:
+      - name: Find Git ref
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        shell: bash
+        run: |
+          PR_NUMBER="${{ github.event.inputs.pr_number || null }}"
+          if test -n "${PR_NUMBER}"; then
+            GIT_REF="$( gh pr view --repo clockworklabs/SpacetimeDB $PR_NUMBER --json headRefName --jq .headRefName )"
+          else
+            GIT_REF="${{ github.ref }}"
+          fi
+          echo "GIT_REF=${GIT_REF}" >>"$GITHUB_ENV"
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ env.GIT_REF }}
+      - uses: dsherret/rust-toolchain-file@v1
+      - name: Set default rust toolchain
+        run: rustup default $(rustup show active-toolchain | cut -d' ' -f1)
+      - name: Cache Rust dependencies
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: ${{ github.workspace }}
+          shared-key: spacetimedb
+          cache-on-failure: false
+          cache-all-crates: true
+          cache-workspace-crates: true
+          prefix-key: v1
+
+      # This step shouldn't be needed, but somehow we end up with caches that are missing librusty_v8.a.
+      # ChatGPT suspects that this could be due to different build invocations using the same target dir,
+      # and this makes sense to me because we only see it in this job where we mix `cargo build -p` with
+      # `cargo build --manifest-path` (which apparently build different dependency trees).
+      # However, we've been unable to fix it so... /shrug
+      - name: Check v8 outputs
+        shell: bash
+        run: |
+          find "${CARGO_TARGET_DIR}"/ -type f | grep '[/_]v8' || true
+          if ! [ -f "${CARGO_TARGET_DIR}"/debug/gn_out/obj/librusty_v8.a ]; then
+            echo "Could not find v8 output file librusty_v8.a; rebuilding manually."
+            cargo clean -p v8 || true
+            cargo build -p v8
+          fi
+
+      - name: Verify crates/smoketests/tests/smoketests/mod.rs lists all entries
+        run: |
+          cargo ci smoketests check-mod-list

crates/smoketests/tests/integration.rs

@@ -0,0 +1,6 @@
+// Single test binary entry point - includes all smoketests
+// We put the tests in a single submodule because if they are at the toplevel then
+// they all build and link independently, which takes a lot of linker time.
+// This has the unfortunate side effect of requiring that they are all listed in a mod.rs,
+// but what can you do ¯\_(ツ)_/¯.
+mod smoketests;