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foxnne merged 1 commit into from
Oct 8, 2026
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ci: a Zig cache is one cold build, saved once #233

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96 changes: 72 additions & 24 deletions .github/workflows/ci.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -76,31 +76,40 @@ jobs:
runs-on: ${{ matrix.os }}
steps:
- uses: actions/checkout@v4
# The cache key, worked out once, here, before anything is unpacked. setup-zig reads its
# `cache-key` input twice — to restore at the start and to save in its post step — and
# GitHub evaluates the expression afresh each time. By the post step the build has
# unpacked every dependency into zig-pkg/, each with its own build.zig.zon, so a
# `hashFiles('**/build.zig.zon')` in the input saved under a hash no restore ever asked
# for: every run missed. A step output is fixed once set.
# The Zig cache's key, worked out once, here, before anything is unpacked. The fetch below
# unpacks every dependency into zig-pkg/, each with its own build.zig.zon, so a
# `hashFiles('**/build.zig.zon')` evaluated after it names a hash no restore ever asked
# for. A step output is fixed once set.
- name: Zig cache key
id: zig-cache-key
shell: bash
run: echo "key=${{ hashFiles('**/build.zig.zon') }}" >> "$GITHUB_OUTPUT"
run: echo "key=zig-${{ env.ZIG_VERSION }}-${{ github.job }}-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('**/build.zig.zon') }}" >> "$GITHUB_OUTPUT"
- uses: mlugg/setup-zig@v2
with:
version: ${{ env.ZIG_VERSION }}
cache-key: ${{ steps.zig-cache-key.outputs.key }}
# MiB. Past it setup-zig clears the cache and saves it empty. A Linux run's cache
# is ~3.5 GB (the tests, the wasm build and four example apps, each compiling its
# own SDL3), so the default 2 GiB threw it away every run.
cache-size-limit: 5120
# setup-zig exports ZIG_GLOBAL_CACHE_DIR / ZIG_LOCAL_CACHE_DIR and caches that
# directory across runs. Do NOT override those vars: pointing them elsewhere
# leaves the action's cache empty, so every run re-downloads every dependency
# from codeload.github.com — which is where `HttpConnectionClosing` comes from.
# (Zig 0.16 caches the downloaded *tarballs* under $ZIG_GLOBAL_CACHE_DIR/p and
# unpacks them into the project-local zig-pkg/; only the tarballs are cached,
# so a cache hit still costs an unpack but no network.)
# The Zig cache is restored and saved by this job's own steps; see below.
use-cache: false
# setup-zig points ZIG_GLOBAL_CACHE_DIR and ZIG_LOCAL_CACHE_DIR at `.zig-cache`, the
# directory cached here. Do NOT override those vars: pointing them elsewhere leaves the
# cache empty, so every run re-downloads every dependency from codeload.github.com —
# which is where `HttpConnectionClosing` comes from. (Zig 0.16 caches the downloaded
# *tarballs* under $ZIG_GLOBAL_CACHE_DIR/p and unpacks them into the project-local
# zig-pkg/; a cache hit still costs an unpack but no network.)
#
# A job's cache is one cold build, saved once; every later run with the same
# dependencies, Zig and OS starts from it. setup-zig's own caching saved every run under
# a new key and restored the newest, so a warm run saved what it restored plus everything
# it rebuilt: Linux's grew from 3.7 GB to 6-7 GB in one run, passed the size limit, and
# was cleared and saved empty, and the run after it started cold. Every other run on
# main built from nothing, and the near-duplicates filled the repo's 10 GB. Here the key
# is fixed and a key can't be overwritten, so only a run that missed saves, and only if
# it succeeded: a run cancelled or failed mid-build never leaves a partial cache behind.
- name: Restore Zig cache
id: zig-cache
uses: actions/cache/restore@v4
with:
path: .zig-cache
key: ${{ steps.zig-cache-key.outputs.key }}
- name: Pre-create Zig cache tmp/
shell: bash
run: mkdir -p "$ZIG_GLOBAL_CACHE_DIR/tmp" "$ZIG_LOCAL_CACHE_DIR/tmp"
Expand Down Expand Up @@ -151,6 +160,13 @@ jobs:
shell: bash
run: bash scripts/ci-retry.sh zig build test-sdk-version --summary all

- name: Save Zig cache
if: success() && steps.zig-cache.outputs.cache-hit != 'true'
uses: actions/cache/save@v4
with:
path: .zig-cache
key: ${{ steps.zig-cache-key.outputs.key }}

# The headless integration tests: real widgets, layouts and drags driven on dvui's testing
# backend (no window, no GPU), plus the SDK, sizing and plugin-loader suites. The suite most
# likely to catch a layout or drag regression, and until this job nothing ran it. Linux only:
Expand All @@ -167,16 +183,21 @@ jobs:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
# See the test job: the key is fixed before anything is unpacked.
# The Zig cache as in the test job: a fixed key, one cold build saved once.
- name: Zig cache key
id: zig-cache-key
shell: bash
run: echo "key=${{ hashFiles('**/build.zig.zon') }}" >> "$GITHUB_OUTPUT"
run: echo "key=zig-${{ env.ZIG_VERSION }}-${{ github.job }}-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('**/build.zig.zon') }}" >> "$GITHUB_OUTPUT"
- uses: mlugg/setup-zig@v2
with:
version: ${{ env.ZIG_VERSION }}
cache-key: ${{ steps.zig-cache-key.outputs.key }}
cache-size-limit: 5120
use-cache: false
- name: Restore Zig cache
id: zig-cache
uses: actions/cache/restore@v4
with:
path: .zig-cache
key: ${{ steps.zig-cache-key.outputs.key }}
- name: Pre-create Zig cache tmp/
shell: bash
run: mkdir -p "$ZIG_GLOBAL_CACHE_DIR/tmp" "$ZIG_LOCAL_CACHE_DIR/tmp"
Expand All @@ -187,6 +208,13 @@ jobs:
shell: bash
run: bash scripts/ci-retry.sh zig build test-integration --summary all

- name: Save Zig cache
if: success() && steps.zig-cache.outputs.cache-hit != 'true'
uses: actions/cache/save@v4
with:
path: .zig-cache
key: ${{ steps.zig-cache-key.outputs.key }}

# Fizzy's own backend on Windows — the default there too now (`build/exe.zig`'s
# `defaultNativeBackend`) — which nothing else here builds: the consumer apps above run on Linux only.
# Cross-compiled from Linux for the GNU ABI, which needs no MSVC SDK (release.yml's msvc
Expand All @@ -198,17 +226,37 @@ jobs:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
# The Zig cache as in the test job. This job's key used to be worked out inline, so
# setup-zig saved under a hash taken after the fetch had unpacked zig-pkg/ and every
# restore missed.
- name: Zig cache key
id: zig-cache-key
shell: bash
run: echo "key=zig-${{ env.ZIG_VERSION }}-${{ github.job }}-${{ runner.os }}-${{ runner.arch }}-${{ hashFiles('**/build.zig.zon') }}" >> "$GITHUB_OUTPUT"
- uses: mlugg/setup-zig@v2
with:
version: ${{ env.ZIG_VERSION }}
cache-key: ${{ hashFiles('**/build.zig.zon') }}
use-cache: false
- name: Restore Zig cache
id: zig-cache
uses: actions/cache/restore@v4
with:
path: .zig-cache
key: ${{ steps.zig-cache-key.outputs.key }}
- name: Pre-create Zig cache tmp/
run: mkdir -p "$ZIG_GLOBAL_CACHE_DIR/tmp" "$ZIG_LOCAL_CACHE_DIR/tmp"
- name: Fetch dependencies (with retries)
run: bash scripts/ci-retry.sh zig build --fetch
- name: Build for x86_64-windows-gnu with -Dnative-backend=fizzy
run: bash scripts/ci-retry.sh zig build -Dtarget=x86_64-windows-gnu -Dnative-backend=fizzy -Dno-emit --summary all

- name: Save Zig cache
if: success() && steps.zig-cache.outputs.cache-hit != 'true'
uses: actions/cache/save@v4
with:
path: .zig-cache
key: ${{ steps.zig-cache-key.outputs.key }}

# The required check. Passes when every job above passed or was skipped (a docs-only change
# skips the builds); fails on any failure or cancellation, `changes` included. A job added to
# this workflow joins the gate by being added to `needs`.
Expand Down
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