# This is our main "CI tests" workflow. It runs everything that should run on
# both PRs and merged commits, and for the latter reports failures to slack.
name: CI

env:
  # Our fuzz job, powered by OSS-Fuzz, fails periodically because we upgrade to
  # new Go versions very eagerly. OSS-Fuzz is a little more conservative, and
  # ends up being unable to compile our code.
  #
  # When this happens, we want to disable the fuzz target until OSS-Fuzz catches
  # up. However, we also don't want to forget to turn it back on when OSS-Fuzz
  # can once again build our code.
  #
  # This variable toggles the fuzz job between two modes:
  #  - false: we expect fuzzing to be happy, and should report failure if it's not.
  #  - true: we expect fuzzing is broken, and should report failure if it start working.
  TS_FUZZ_CURRENTLY_BROKEN: false

on:
  push:
    branches:
      - "main"
      - "release-branch/*"
  pull_request:
    branches:
      - "*"
  merge_group:
    branches:
      - "main"

concurrency:
  # For PRs, later CI runs preempt previous ones. e.g. a force push on a PR
  # cancels running CI jobs and starts all new ones.
  #
  # For non-PR pushes, concurrency.group needs to be unique for every distinct
  # CI run we want to have happen. Use run_id, which in practice means all
  # non-PR CI runs will be allowed to run without preempting each other.
  group: ${{ github.workflow }}-$${{ github.pull_request.number || github.run_id }}
  cancel-in-progress: true

jobs:
  test:
    strategy:
      fail-fast: false # don't abort the entire matrix if one element fails
      matrix:
        goarch: ["amd64", "386"]
        # go list -json ./... | jq -c -s '[.[].ImportPath]'
        #pkg: ["tailscale.com","tailscale.com/atomicfile","tailscale.com/chirp","tailscale.com/client/tailscale","tailscale.com/client/tailscale/apitype","tailscale.com/client/tailscale/example/servetls","tailscale.com/client/web","tailscale.com/clientupdate","tailscale.com/clientupdate/distsign","tailscale.com/cmd/addlicense","tailscale.com/cmd/cloner","tailscale.com/cmd/derper","tailscale.com/cmd/derpprobe","tailscale.com/cmd/dist","tailscale.com/cmd/get-authkey","tailscale.com/cmd/gitops-pusher","tailscale.com/cmd/hello","tailscale.com/cmd/k8s-operator","tailscale.com/cmd/mkmanifest","tailscale.com/cmd/mkpkg","tailscale.com/cmd/mkversion","tailscale.com/cmd/nardump","tailscale.com/cmd/netlogfmt","tailscale.com/cmd/pgproxy","tailscale.com/cmd/printdep","tailscale.com/cmd/proxy-to-grafana","tailscale.com/cmd/sniproxy","tailscale.com/cmd/speedtest","tailscale.com/cmd/ssh-auth-none-demo","tailscale.com/cmd/stunc","tailscale.com/cmd/sync-containers","tailscale.com/cmd/tailscale","tailscale.com/cmd/tailscale/cli","tailscale.com/cmd/tailscaled","tailscale.com/cmd/tailscaled/childproc","tailscale.com/cmd/testcontrol","tailscale.com/cmd/testwrapper","tailscale.com/cmd/testwrapper/flakytest","tailscale.com/cmd/tsconnect","tailscale.com/cmd/viewer","tailscale.com/cmd/viewer/tests","tailscale.com/control/controlbase","tailscale.com/control/controlclient","tailscale.com/control/controlhttp","tailscale.com/control/controlknobs","tailscale.com/derp","tailscale.com/derp/derphttp","tailscale.com/disco","tailscale.com/docs/webhooks","tailscale.com/doctor","tailscale.com/doctor/permissions","tailscale.com/doctor/routetable","tailscale.com/envknob","tailscale.com/envknob/logknob","tailscale.com/health","tailscale.com/health/healthmsg","tailscale.com/hostinfo","tailscale.com/ipn","tailscale.com/ipn/ipnauth","tailscale.com/ipn/ipnlocal","tailscale.com/ipn/ipnserver","tailscale.com/ipn/ipnstate","tailscale.com/ipn/localapi","tailscale.com/ipn/policy","tailscale.com/ipn/store","tailscale.com/ipn/store/awsstore","tailscale.com/ipn/store/kubestore","tailscale.com/ipn/store/mem","tailscale.com/jsondb","tailscale.com/kube","tailscale.com/licenses","tailscale.com/log/filelogger","tailscale.com/log/sockstatlog","tailscale.com/logpolicy","tailscale.com/logtail","tailscale.com/logtail/backoff","tailscale.com/logtail/example/logadopt","tailscale.com/logtail/example/logreprocess","tailscale.com/logtail/example/logtail","tailscale.com/logtail/filch","tailscale.com/metrics","tailscale.com/net/art","tailscale.com/net/connstats","tailscale.com/net/dns","tailscale.com/net/dns/publicdns","tailscale.com/net/dns/recursive","tailscale.com/net/dns/resolvconffile","tailscale.com/net/dns/resolver","tailscale.com/net/dnscache","tailscale.com/net/dnsfallback","tailscale.com/net/flowtrack","tailscale.com/net/interfaces","tailscale.com/net/memnet","tailscale.com/net/netaddr","tailscale.com/net/netcheck","tailscale.com/net/neterror","tailscale.com/net/netknob","tailscale.com/net/netmon","tailscale.com/net/netns","tailscale.com/net/netstat","tailscale.com/net/netutil","tailscale.com/net/packet","tailscale.com/net/ping","tailscale.com/net/portmapper","tailscale.com/net/proxymux","tailscale.com/net/routetable","tailscale.com/net/socks5","tailscale.com/net/sockstats","tailscale.com/net/speedtest","tailscale.com/net/stun","tailscale.com/net/stun/stuntest","tailscale.com/net/tcpinfo","tailscale.com/net/tlsdial","tailscale.com/net/tsaddr","tailscale.com/net/tsdial","tailscale.com/net/tshttpproxy","tailscale.com/net/tstun","tailscale.com/net/tstun/table","tailscale.com/net/wsconn","tailscale.com/packages/deb","tailscale.com/paths","tailscale.com/portlist","tailscale.com/prober","tailscale.com/release","tailscale.com/release/dist","tailscale.com/release/dist/cli","tailscale.com/release/dist/synology","tailscale.com/release/dist/unixpkgs","tailscale.com/safesocket","tailscale.com/smallzstd","tailscale.com/ssh/tailssh","tailscale.com/syncs","tailscale.com/tailcfg","tailscale.com/tempfork/device","tailscale.com/tempfork/gliderlabs/ssh","tailscale.com/tempfork/heap","tailscale.com/tempfork/pprof","tailscale.com/tka","tailscale.com/tool/gocross","tailscale.com/tsconst","tailscale.com/tsd","tailscale.com/tsnet","tailscale.com/tsnet/example/tshello","tailscale.com/tsnet/example/tsnet-funnel","tailscale.com/tsnet/example/tsnet-http-client","tailscale.com/tsnet/example/web-client","tailscale.com/tstest","tailscale.com/tstest/archtest","tailscale.com/tstest/deptest","tailscale.com/tstest/integration","tailscale.com/tstest/integration/testcontrol","tailscale.com/tstest/integration/vms","tailscale.com/tstest/integration/vms/gen","tailscale.com/tstest/iosdeps","tailscale.com/tstest/jsdeps","tailscale.com/tstest/natlab","tailscale.com/tstime","tailscale.com/tstime/mono","tailscale.com/tstime/rate","tailscale.com/tsweb","tailscale.com/tsweb/promvarz","tailscale.com/tsweb/varz","tailscale.com/types/dnstype","tailscale.com/types/empty","tailscale.com/types/flagtype","tailscale.com/types/ipproto","tailscale.com/types/key","tailscale.com/types/lazy","tailscale.com/types/logger","tailscale.com/types/logid","tailscale.com/types/netlogtype","tailscale.com/types/netmap","tailscale.com/types/nettype","tailscale.com/types/opt","tailscale.com/types/persist","tailscale.com/types/preftype","tailscale.com/types/ptr","tailscale.com/types/structs","tailscale.com/types/tkatype","tailscale.com/types/views","tailscale.com/util/cibuild","tailscale.com/util/clientmetric","tailscale.com/util/cloudenv","tailscale.com/util/cmpver","tailscale.com/util/cmpx","tailscale.com/util/codegen","tailscale.com/util/cstruct","tailscale.com/util/deephash","tailscale.com/util/deephash/testtype","tailscale.com/util/dirwalk","tailscale.com/util/dnsname","tailscale.com/util/goroutines","tailscale.com/util/groupmember","tailscale.com/util/hashx","tailscale.com/util/httpm","tailscale.com/util/jsonutil","tailscale.com/util/lineread","tailscale.com/util/linuxfw","tailscale.com/util/linuxfw/linuxfwtest","tailscale.com/util/lru","tailscale.com/util/mak","tailscale.com/util/multierr","tailscale.com/util/must","tailscale.com/util/osdiag","tailscale.com/util/osshare","tailscale.com/util/pidowner","tailscale.com/util/precompress","tailscale.com/util/quarantine","tailscale.com/util/racebuild","tailscale.com/util/ringbuffer","tailscale.com/util/set","tailscale.com/util/singleflight","tailscale.com/util/slicesx","tailscale.com/util/sysresources","tailscale.com/util/systemd","tailscale.com/util/testenv","tailscale.com/util/truncate","tailscale.com/util/uniq","tailscale.com/util/vizerror","tailscale.com/util/winutil","tailscale.com/util/winutil/authenticode","tailscale.com/version","tailscale.com/version/distro","tailscale.com/version/mkversion","tailscale.com/wgengine","tailscale.com/wgengine/bench","tailscale.com/wgengine/capture","tailscale.com/wgengine/filter","tailscale.com/wgengine/magicsock","tailscale.com/wgengine/netlog","tailscale.com/wgengine/netstack","tailscale.com/wgengine/router","tailscale.com/wgengine/wgcfg","tailscale.com/wgengine/wgcfg/nmcfg","tailscale.com/wgengine/wgint","tailscale.com/wgengine/wglog","tailscale.com/words"]
        pkg: ["tailscale.com","tailscale.com/atomicfile","tailscale.com/chirp","tailscale.com/client/tailscale"]
        buildflags: ["-race=false"]
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: Restore Cache
      uses: actions/cache@v3
      with:
        # Note: unlike the other setups, this is only grabbing the mod download
        # cache, rather than the whole mod directory, as the download cache
        # contains zips that can be unpacked in parallel faster than they can be
        # fetched and extracted by tar
        path: |
          ~/.cache/go-build
          ~/go/pkg/mod/cache
          ~\AppData\Local\go-build
        # The -2- here should be incremented when the scheme of data to be
        # cached changes (e.g. path above changes).
        key: ${{ github.job }}-${{ runner.os }}-${{ matrix.pkg }}-${{ matrix.goarch }}-${{ matrix.buildflags }}-go-2-${{ hashFiles('**/go.sum') }}-${{ github.run_id }}
        restore-keys: |
          ${{ github.job }}-${{ runner.os }}-${{ matrix.pkg }}-${{ matrix.goarch }}-${{ matrix.buildflags }}-go-2-${{ hashFiles('**/go.sum') }}
          ${{ github.job }}-${{ runner.os }}-${{ matrix.pkg }}-${{ matrix.goarch }}-${{ matrix.buildflags }}-go-2-
    - name: build test wrapper
      run: ./tool/go build -o /tmp/testwrapper ./cmd/testwrapper
    - name: test all
      run: PATH=$PWD/tool:$PATH /tmp/testwrapper ${{matrix.pkg}} ${{matrix.buildflags}}
      env:
        GOARCH: ${{ matrix.goarch }}
    - name: check that no tracked files changed
      run: git diff --no-ext-diff --name-only --exit-code || (echo "Build/test modified the files above."; exit 1)
    - name: check that no new files were added
      run: |
        # Note: The "error: pathspec..." you see below is normal!
        # In the success case in which there are no new untracked files,
        # git ls-files complains about the pathspec not matching anything.
        # That's OK. It's not worth the effort to suppress. Please ignore it.
        if git ls-files --others --exclude-standard --directory --no-empty-directory --error-unmatch -- ':/*'
        then
          echo "Build/test created untracked files in the repo (file names above)."
          exit 1
        fi

  windows:
    runs-on: windows-2022
    steps:
    - name: checkout
      uses: actions/checkout@v3

    - name: Install Go
      uses: actions/setup-go@v4
      with:
        go-version-file: go.mod
        cache: false

    - name: Restore Cache
      uses: actions/cache@v3
      with:
        # Note: unlike the other setups, this is only grabbing the mod download
        # cache, rather than the whole mod directory, as the download cache
        # contains zips that can be unpacked in parallel faster than they can be
        # fetched and extracted by tar
        path: |
          ~/.cache/go-build
          ~/go/pkg/mod/cache
          ~\AppData\Local\go-build
        # The -2- here should be incremented when the scheme of data to be
        # cached changes (e.g. path above changes).
        key: ${{ github.job }}-${{ runner.os }}-go-2-${{ hashFiles('**/go.sum') }}-${{ github.run_id }}
        restore-keys: |
          ${{ github.job }}-${{ runner.os }}-go-2-${{ hashFiles('**/go.sum') }}
          ${{ github.job }}-${{ runner.os }}-go-2-
    - name: test
      run: go run ./cmd/testwrapper ./...
    - name: bench all
      # Don't use -bench=. -benchtime=1x.
      # Somewhere in the layers (powershell?)
      # the equals signs cause great confusion.
      run: go test ./... -bench . -benchtime 1x -run "^$"

  vm:
    runs-on: ["self-hosted", "linux", "vm"]
    # VM tests run with some privileges, don't let them run on 3p PRs.
    if: github.repository == 'tailscale/tailscale'
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: Run VM tests
      run: ./tool/go test ./tstest/integration/vms -v -no-s3 -run-vm-tests -run=TestRunUbuntu2004
      env:
        HOME: "/tmp"
        TMPDIR: "/tmp"
        XDB_CACHE_HOME: "/var/lib/ghrunner/cache"
  
  cross: # cross-compile checks, build only.
    strategy:
      fail-fast: false # don't abort the entire matrix if one element fails
      matrix:
        include:
          # Note: linux/amd64 is not in this matrix, because that goos/goarch is
          # tested more exhaustively in the 'test' job above.
          - goos: linux
            goarch: arm64
          - goos: linux
            goarch: "386" # thanks yaml
          - goos: linux
            goarch: loong64
          - goos: linux
            goarch: arm
            goarm: "5"
          - goos: linux
            goarch: arm
            goarm: "7"
          # macOS
          - goos: darwin
            goarch: amd64
          - goos: darwin
            goarch: arm64
          # Windows
          - goos: windows
            goarch: amd64
          - goos: windows
            goarch: arm64
          # BSDs
          - goos: freebsd
            goarch: amd64
          - goos: openbsd
            goarch: amd64
          # Plan9
          - goos: plan9
            goarch: amd64

    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: Restore Cache
      uses: actions/cache@v3
      with:
        # Note: unlike the other setups, this is only grabbing the mod download
        # cache, rather than the whole mod directory, as the download cache
        # contains zips that can be unpacked in parallel faster than they can be
        # fetched and extracted by tar
        path: |
          ~/.cache/go-build
          ~/go/pkg/mod/cache
          ~\AppData\Local\go-build
        # The -2- here should be incremented when the scheme of data to be
        # cached changes (e.g. path above changes).
        key: ${{ github.job }}-${{ runner.os }}-${{ matrix.goos }}-${{ matrix.goarch }}-go-2-${{ hashFiles('**/go.sum') }}-${{ github.run_id }}
        restore-keys: |
          ${{ github.job }}-${{ runner.os }}-${{ matrix.goos }}-${{ matrix.goarch }}-go-2-${{ hashFiles('**/go.sum') }}
          ${{ github.job }}-${{ runner.os }}-${{ matrix.goos }}-${{ matrix.goarch }}-go-2-
    - name: build all
      run: ./tool/go build ./cmd/...
      env:
        GOOS: ${{ matrix.goos }}
        GOARCH: ${{ matrix.goarch }}
        GOARM: ${{ matrix.goarm }}
        CGO_ENABLED: "0"
    - name: build tests
      run: ./tool/go test -exec=true ./...
      env:
        GOOS: ${{ matrix.goos }}
        GOARCH: ${{ matrix.goarch }}
        CGO_ENABLED: "0"

  ios: # similar to cross above, but iOS can't build most of the repo. So, just
       #make it build a few smoke packages.
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: build some
      run: ./tool/go build ./ipn/... ./wgengine/ ./types/... ./control/controlclient
      env:
        GOOS: ios
        GOARCH: arm64

  android:
    # similar to cross above, but android fails to build a few pieces of the
    # repo. We should fix those pieces, they're small, but as a stepping stone,
    # only test the subset of android that our past smoke test checked.
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
      # Super minimal Android build that doesn't even use CGO and doesn't build everything that's needed
      # and is only arm64. But it's a smoke build: it's not meant to catch everything. But it'll catch
      # some Android breakages early.
      # TODO(bradfitz): better; see https://github.com/tailscale/tailscale/issues/4482
    - name: build some
      run: ./tool/go install ./net/netns ./ipn/ipnlocal ./wgengine/magicsock/ ./wgengine/ ./wgengine/router/ ./wgengine/netstack ./util/dnsname/ ./ipn/ ./net/interfaces ./wgengine/router/ ./tailcfg/ ./types/logger/ ./net/dns ./hostinfo ./version
      env:
        GOOS: android
        GOARCH: arm64

  wasm: # builds tsconnect, which is the only wasm build we support
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: Restore Cache
      uses: actions/cache@v3
      with:
        # Note: unlike the other setups, this is only grabbing the mod download
        # cache, rather than the whole mod directory, as the download cache
        # contains zips that can be unpacked in parallel faster than they can be
        # fetched and extracted by tar
        path: |
          ~/.cache/go-build
          ~/go/pkg/mod/cache
          ~\AppData\Local\go-build
        # The -2- here should be incremented when the scheme of data to be
        # cached changes (e.g. path above changes).
        key: ${{ github.job }}-${{ runner.os }}-go-2-${{ hashFiles('**/go.sum') }}-${{ github.run_id }}
        restore-keys: |
          ${{ github.job }}-${{ runner.os }}-go-2-${{ hashFiles('**/go.sum') }}
          ${{ github.job }}-${{ runner.os }}-go-2-
    - name: build tsconnect client
      run: ./tool/go build ./cmd/tsconnect/wasm ./cmd/tailscale/cli
      env:
        GOOS: js
        GOARCH: wasm
    - name: build tsconnect server
      # Note, no GOOS/GOARCH in env on this build step, we're running a build
      # tool that handles the build itself.
      run: |
        ./tool/go run ./cmd/tsconnect --fast-compression build
        ./tool/go run ./cmd/tsconnect --fast-compression build-pkg

  tailscale_go: # Subset of tests that depend on our custom Go toolchain.
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: test tailscale_go
      run: ./tool/go test -tags=tailscale_go,ts_enable_sockstats ./net/sockstats/...


  fuzz:
    # This target periodically breaks (see TS_FUZZ_CURRENTLY_BROKEN at the top
    # of the file), so it's more complex than usual: the 'build fuzzers' step
    # might fail, and depending on the value of 'TS_FUZZ_CURRENTLY_BROKEN', that
    # might or might not be fine. The steps after the build figure out whether
    # the success/failure is expected, and appropriately pass/fail the job
    # overall accordingly.
    #
    # Practically, this means that all steps after 'build fuzzers' must have an
    # explicit 'if' condition, because the default condition for steps is
    # 'success()', meaning "only run this if no previous steps failed".
    if: github.event_name == 'pull_request'
    runs-on: ubuntu-22.04
    steps:
    - name: build fuzzers
      id: build
      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
      # continue-on-error makes steps.build.conclusion be 'success' even if
      # steps.build.outcome is 'failure'. This means this step does not
      # contribute to the job's overall pass/fail evaluation.
      continue-on-error: true
      with:
       oss-fuzz-project-name: 'tailscale'
       dry-run: false
       language: go
    - name: report unexpectedly broken fuzz build
      if: steps.build.outcome == 'failure' && env.TS_FUZZ_CURRENTLY_BROKEN != 'true'
      run: |
        echo "fuzzer build failed, see above for why"
        echo "if the failure is due to OSS-Fuzz not being on the latest Go yet,"
        echo "set TS_FUZZ_CURRENTLY_BROKEN=true in .github/workflows/test.yml"
        echo "to temporarily disable fuzzing until OSS-Fuzz works again."
        exit 1
    - name: report unexpectedly working fuzz build
      if: steps.build.outcome == 'success' && env.TS_FUZZ_CURRENTLY_BROKEN == 'true'
      run: |
        echo "fuzzer build succeeded, but we expect it to be broken"
        echo "please set TS_FUZZ_CURRENTLY_BROKEN=false in .github/workflows/test.yml"
        echo "to reenable fuzz testing"
        exit 1
    - name: run fuzzers
      id: run
      # Run the fuzzers whenever they're able to build, even if we're going to
      # report a failure because TS_FUZZ_CURRENTLY_BROKEN is set to the wrong
      # value.
      if: steps.build.outcome == 'success'
      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
      with:
        oss-fuzz-project-name: 'tailscale'
        fuzz-seconds: 300
        dry-run: false
        language: go
    - name: upload crash
      uses: actions/upload-artifact@v3
      if: steps.run.outcome != 'success' && steps.build.outcome == 'success'
      with:
        name: artifacts
        path: ./out/artifacts

  depaware:
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: check depaware
      run: |
        export PATH=$(./tool/go env GOROOT)/bin:$PATH
        find . -name 'depaware.txt' | xargs -n1 dirname | xargs ./tool/go run github.com/tailscale/depaware --check

  go_generate:
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: check that 'go generate' is clean
      run: |
        pkgs=$(./tool/go list ./... | grep -v dnsfallback)
        ./tool/go generate $pkgs
        echo
        echo
        git diff --name-only --exit-code || (echo "The files above need updating. Please run 'go generate'."; exit 1)

  go_mod_tidy:
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: check that 'go mod tidy' is clean
      run: |
        ./tool/go mod tidy
        echo
        echo
        git diff --name-only --exit-code || (echo "Please run 'go mod tidy'."; exit 1)

  licenses:
    runs-on: ubuntu-22.04
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: check licenses
      run: ./scripts/check_license_headers.sh .

  staticcheck:
    runs-on: ubuntu-22.04
    strategy:
      fail-fast: false # don't abort the entire matrix if one element fails
      matrix:
        goos: ["linux", "windows", "darwin"]
        goarch: ["amd64"]
        include:
          - goos: "windows"
            goarch: "386"
    steps:
    - name: checkout
      uses: actions/checkout@v3
    - name: install staticcheck
      run: GOBIN=~/.local/bin ./tool/go install honnef.co/go/tools/cmd/staticcheck
    - name: run staticcheck
      run: |
        export GOROOT=$(./tool/go env GOROOT)
        export PATH=$GOROOT/bin:$PATH
        staticcheck -- $(./tool/go list ./... | grep -v tempfork)
      env:
        GOOS: ${{ matrix.goos }}
        GOARCH: ${{ matrix.goarch }}

  notify_slack:
    if: always()
    # Any of these jobs failing causes a slack notification.
    needs: 
      - android
      - test
      - windows
      - vm
      - cross
      - ios
      - wasm
      - tailscale_go
      - fuzz
      - depaware
      - go_generate
      - go_mod_tidy
      - licenses
      - staticcheck
    runs-on: ubuntu-22.04
    steps:
    - name: notify  
      # Only notify slack for merged commits, not PR failures.
      #
      # It may be tempting to move this condition into the job's 'if' block, but
      # don't: Github only collapses the test list into "everything is OK" if
      # all jobs succeeded. A skipped job results in the list staying expanded.
      # By having the job always run, but skipping its only step as needed, we
      # let the CI output collapse nicely in PRs.
      if: failure() && github.event_name == 'push'
      uses: ruby/action-slack@v3.2.1
      with:
        payload: |
          {
            "attachments": [{
              "title": "Failure: ${{ github.workflow }}",
              "title_link": "https://github.com/${{ github.repository }}/commit/${{ github.sha }}/checks",         
              "text": "${{ github.repository }}@${{ github.ref_name }}: <https://github.com/${{ github.repository }}/commit/${{ github.sha }}|${{ github.sha }}>",
              "fields": [{ "value": ${{ toJson(github.event.head_commit.message) }}, "short": false }],
              "footer": "${{ github.event.head_commit.committer.name }} at ${{ github.event.head_commit.timestamp }}",
              "color": "danger"
            }]
          }
      env:
        SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK_URL }}

  check_mergeability:
    if: always()
    runs-on: ubuntu-22.04
    needs:
      - android
      - test
      - windows
      - vm
      - cross
      - ios
      - wasm
      - tailscale_go
      - fuzz
      - depaware
      - go_generate
      - go_mod_tidy
      - licenses
      - staticcheck
    steps:
    - name: Decide if change is okay to merge
      if: github.event_name != 'push'
      uses: re-actors/alls-green@release/v1
      with:
        jobs: ${{ toJSON(needs) }}