b5b968e103
Change-Id: Id3365c18bc3904b42e8b129a513cff4480a2cb07 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7051 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
446 lines
16 KiB
Nix
446 lines
16 KiB
Nix
# Logic for generating Buildkite pipelines from Nix build targets read
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# by //nix/readTree.
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#
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# It outputs a "YAML" (actually JSON) file which is evaluated and
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# submitted to Buildkite at the start of each build.
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#
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# The structure of the file that is being created is documented here:
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# https://buildkite.com/docs/pipelines/defining-steps
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{ depot, pkgs, ... }:
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let
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inherit (builtins)
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attrValues
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concatLists
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concatStringsSep
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elem
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foldl'
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hasAttr
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hashString
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isNull
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isString
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length
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listToAttrs
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mapAttrs
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toJSON
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unsafeDiscardStringContext;
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inherit (pkgs) lib runCommand writeText;
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inherit (depot.nix.readTree) mkLabel;
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in
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rec {
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# Creates a Nix expression that yields the target at the specified
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# location in the repository.
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#
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# This makes a distinction between normal targets (which physically
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# exist in the repository) and subtargets (which are "virtual"
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# targets exposed by a physical one) to make it clear in the build
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# output which is which.
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mkBuildExpr = target:
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let
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descend = expr: attr: "builtins.getAttr \"${attr}\" (${expr})";
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targetExpr = foldl' descend "import ./. {}" target.__readTree;
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subtargetExpr = descend targetExpr target.__subtarget;
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in
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if target ? __subtarget then subtargetExpr else targetExpr;
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# Determine whether to skip a target if it has not diverged from the
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# HEAD branch.
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shouldSkip = parentTargetMap: label: drvPath:
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if (hasAttr label parentTargetMap) && parentTargetMap."${label}".drvPath == drvPath
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then "Target has not changed."
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else false;
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# Create build command for a derivation target.
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mkBuildCommand = target: drvPath: concatStringsSep " " [
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# First try to realise the drvPath of the target so we don't evaluate twice.
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# Nix has no concept of depending on a derivation file without depending on
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# at least one of its `outPath`s, so we need to discard the string context
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# if we don't want to build everything during pipeline construction.
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"(nix-store --realise '${drvPath}' --add-root result --indirect && readlink result)"
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# Since we don't gcroot the derivation files, they may be deleted by the
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# garbage collector. In that case we can reevaluate and build the attribute
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# using nix-build.
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"|| (test ! -f '${drvPath}' && nix-build -E '${mkBuildExpr target}' --show-trace)"
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];
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# Create a pipeline step from a single target.
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mkStep = headBranch: parentTargetMap: target: cancelOnBuildFailing:
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let
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label = mkLabel target;
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drvPath = unsafeDiscardStringContext target.drvPath;
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shouldSkip' = shouldSkip parentTargetMap;
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in
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{
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label = ":nix: " + label;
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key = hashString "sha1" label;
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skip = shouldSkip' label drvPath;
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command = mkBuildCommand target drvPath;
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env.READTREE_TARGET = label;
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cancel_on_build_failing = cancelOnBuildFailing;
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# Add a dependency on the initial static pipeline step which
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# always runs. This allows build steps uploaded in batches to
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# start running before all batches have been uploaded.
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depends_on = ":init:";
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};
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# Helper function to inelegantly divide a list into chunks of at
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# most n elements.
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#
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# This works by assigning each element a chunk ID based on its
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# index, and then grouping all elements by their chunk ID.
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chunksOf = n: list:
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let
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chunkId = idx: toString (idx / n + 1);
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assigned = lib.imap1 (idx: value: { inherit value; chunk = chunkId idx; }) list;
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unchunk = mapAttrs (_: elements: map (e: e.value) elements);
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in
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unchunk (lib.groupBy (e: e.chunk) assigned);
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# Define a build pipeline chunk as a JSON file, using the pipeline
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# format documented on
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# https://buildkite.com/docs/pipelines/defining-steps.
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makePipelineChunk = name: chunkId: chunk: rec {
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filename = "${name}-chunk-${chunkId}.json";
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path = writeText filename (toJSON {
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steps = chunk;
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});
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};
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# Split the pipeline into chunks of at most 192 steps at once, which
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# are uploaded sequentially. This is because of a limitation in the
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# Buildkite backend which struggles to process more than a specific
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# number of chunks at once.
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pipelineChunks = name: steps:
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attrValues (mapAttrs (makePipelineChunk name) (chunksOf 192 steps));
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# Create a pipeline structure for the given targets.
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mkPipeline =
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{
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# HEAD branch of the repository on which release steps, GC
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# anchoring and other "mainline only" steps should run.
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headBranch
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, # List of derivations as read by readTree (in most cases just the
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# output of readTree.gather) that should be built in Buildkite.
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#
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# These are scheduled as the first build steps and run as fast as
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# possible, in order, without any concurrency restrictions.
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drvTargets
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, # Derivation map of a parent commit. Only targets which no longer
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# correspond to the content of this map will be built. Passing an
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# empty map will always build all targets.
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parentTargetMap ? { }
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, # A list of plain Buildkite step structures to run alongside the
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# build for all drvTargets, but before proceeding with any
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# post-build actions such as status reporting.
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#
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# Can be used for things like code formatting checks.
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additionalSteps ? [ ]
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, # A list of plain Buildkite step structures to run after all
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# previous steps succeeded.
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#
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# Can be used for status reporting steps and the like.
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postBuildSteps ? [ ]
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# The list of phases known by the current Buildkite
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# pipeline. Dynamic pipeline chunks for each phase are uploaded
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# to Buildkite on execution of static part of the
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# pipeline. Phases selection is hard-coded in the static
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# pipeline.
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#
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# Pipeline generation will fail when an extra step with
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# unregistered phase is added.
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#
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# Common scenarios for different phase:
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# - "build" - main phase for building all Nix targets
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# - "release" - pushing artifacts to external repositories
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# - "deploy" - updating external deployment configurations
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, phases ? [ "build" "release" ]
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# Build phases that are active for this invocation (i.e. their
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# steps should be generated).
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#
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# This can be used to disable outputting parts of a pipeline if,
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# for example, build and release phases are created in separate
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# eval contexts.
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#
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# TODO(tazjin): Fail/warn if unknown phase is requested.
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, activePhases ? phases
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# Setting this attribute to true cancels dynamic pipeline steps
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# as soon as the build is marked as failing.
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#
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# To enable this feature one should enable "Fail Fast" setting
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# at Buildkite pipeline or on organization level.
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, cancelOnBuildFailing ? false
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}:
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let
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# List of phases to include.
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enabledPhases = lib.intersectLists activePhases phases;
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# Is the 'build' phase included? This phase is treated specially
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# because it always contains the plain Nix builds, and some
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# logic/optimisation depends on knowing whether is executing.
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buildEnabled = elem "build" enabledPhases;
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# Convert a target into all of its steps, separated by build
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# phase (as phases end up in different chunks).
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targetToSteps = target:
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let
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step = mkStep headBranch parentTargetMap target cancelOnBuildFailing;
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# Same step, but with an override function applied. This is
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# used in mkExtraStep if the extra step needs to modify the
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# parent derivation somehow.
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#
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# Note that this will never affect the label.
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overridable = f: mkStep headBranch parentTargetMap (f target) cancelOnBuildFailing;
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# Split extra steps by phase.
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splitExtraSteps = lib.groupBy ({ phase, ... }: phase)
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(attrValues (mapAttrs (normaliseExtraStep phases overridable)
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(target.meta.ci.extraSteps or { })));
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extraSteps = mapAttrs
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(_: steps:
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map (mkExtraStep buildEnabled) steps)
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splitExtraSteps;
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in
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if !buildEnabled then extraSteps
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else extraSteps // {
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build = [ step ] ++ (extraSteps.build or [ ]);
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};
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# Combine all target steps into step lists per phase.
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#
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# TODO(tazjin): Refactor when configurable phases show up.
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globalSteps = {
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build = additionalSteps;
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release = postBuildSteps;
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};
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phasesWithSteps = lib.zipAttrsWithNames enabledPhases (_: concatLists)
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((map targetToSteps drvTargets) ++ [ globalSteps ]);
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# Generate pipeline chunks for each phase.
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chunks = foldl'
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(acc: phase:
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let phaseSteps = phasesWithSteps.${phase} or [ ]; in
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if phaseSteps == [ ]
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then acc
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else acc ++ (pipelineChunks phase phaseSteps))
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[ ]
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enabledPhases;
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in
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runCommand "buildkite-pipeline" { } ''
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mkdir $out
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echo "Generated ${toString (length chunks)} pipeline chunks"
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${
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lib.concatMapStringsSep "\n"
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(chunk: "cp ${chunk.path} $out/${chunk.filename}") chunks
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}
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'';
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# Create a drvmap structure for the given targets, containing the
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# mapping of all target paths to their derivations. The mapping can
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# be persisted for future use.
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mkDrvmap = drvTargets: writeText "drvmap.json" (toJSON (listToAttrs (map
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(target: {
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name = mkLabel target;
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value = {
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drvPath = unsafeDiscardStringContext target.drvPath;
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# Include the attrPath in the output to reconstruct the drv
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# without parsing the human-readable label.
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attrPath = target.__readTree ++ lib.optionals (target ? __subtarget) [
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target.__subtarget
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];
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};
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})
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drvTargets)));
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# Implementation of extra step logic.
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#
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# Each target extra step is an attribute specified in
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# `meta.ci.extraSteps`. Its attribute name will be used as the step
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# name on Buildkite.
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#
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# command (required): A command that will be run in the depot
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# checkout when this step is executed. Should be a derivation
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# resulting in a single executable file, e.g. through
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# pkgs.writeShellScript.
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#
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# label (optional): Human-readable label for this step to display
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# in the Buildkite UI instead of the attribute name.
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#
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# prompt (optional): Setting this blocks the step until confirmed
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# by a human. Should be a string which is displayed for
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# confirmation. These steps always run after the main build is
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# done and have no influence on CI status.
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#
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# postBuild (optional): If set to true, this step will run after
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# all primary build steps (that is, after status has been reported
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# back to CI).
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#
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# needsOutput (optional): If set to true, the parent derivation
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# will be built in the working directory before running the
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# command. Output will be available as 'result'.
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# TODO: Figure out multiple-output derivations.
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#
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# parentOverride (optional): A function (drv -> drv) to override
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# the parent's target definition when preparing its output. Only
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# used in extra steps that use needsOutput.
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#
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# branches (optional): Git references (branches, tags ... ) on
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# which this step should be allowed to run. List of strings.
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#
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# alwaysRun (optional): If set to true, this step will always run,
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# even if its parent has not been rebuilt.
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#
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# Note that gated steps are independent of each other.
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# Create a gated step in a step group, independent from any other
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# steps.
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mkGatedStep = { step, label, parent, prompt }: {
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inherit (step) depends_on;
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group = label;
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skip = parent.skip or false;
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steps = [
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{
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inherit prompt;
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branches = step.branches or [ ];
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block = ":radio_button: Run ${label}? (from ${parent.env.READTREE_TARGET})";
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}
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# The explicit depends_on of the wrapped step must be removed,
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# otherwise its dependency relationship with the gate step will
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# break.
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(builtins.removeAttrs step [ "depends_on" ])
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];
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};
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# Validate and normalise extra step configuration before actually
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# generating build steps, in order to use user-provided metadata
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# during the pipeline generation.
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normaliseExtraStep = phases: overridableParent: key:
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{ command
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, label ? key
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, needsOutput ? false
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, parentOverride ? (x: x)
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, branches ? null
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, alwaysRun ? false
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, prompt ? false
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# TODO(tazjin): Default to 'build' after 2022-10-01.
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, phase ? if (isNull postBuild || !postBuild) then "build" else "release"
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# TODO(tazjin): Turn into hard-failure after 2022-10-01.
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, postBuild ? null
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, skip ? false
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, agents ? null
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}:
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let
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parent = overridableParent parentOverride;
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parentLabel = parent.env.READTREE_TARGET;
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validPhase = lib.throwIfNot (elem phase phases) ''
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In step '${label}' (from ${parentLabel}):
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Phase '${phase}' is not valid.
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Known phases: ${concatStringsSep ", " phases}
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''
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phase;
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in
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{
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inherit
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alwaysRun
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branches
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command
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key
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label
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needsOutput
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parent
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parentLabel
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skip
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agents;
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# //nix/buildkite is growing a new feature for adding different
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# "build phases" which supersedes the previous `postBuild`
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# boolean API.
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#
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# To help users transition, emit warnings if the old API is used.
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phase = lib.warnIfNot (isNull postBuild) ''
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In step '${label}' (from ${parentLabel}):
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Please note: The CI system is introducing support for running
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steps in different build phases.
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The currently supported phases are 'build' (all Nix targets,
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extra steps such as tests that feed into the build results,
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etc.) and 'release' (steps that run after builds and tests
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have already completed).
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This replaces the previous boolean `postBuild` API in extra
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step definitions. Please remove the `postBuild` parameter from
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this step and instead set `phase = ${phase};`.
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''
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validPhase;
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prompt = lib.throwIf (prompt != false && phase == "build") ''
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In step '${label}' (from ${parentLabel}):
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The 'prompt' feature can only be used by steps in the "release"
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phase, because CI builds should not be gated on manual human
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approvals.
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''
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prompt;
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};
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# Create the Buildkite configuration for an extra step, optionally
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# wrapping it in a gate group.
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mkExtraStep = buildEnabled: cfg:
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let
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step = {
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label = ":gear: ${cfg.label} (from ${cfg.parentLabel})";
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skip =
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let
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# When parent doesn't have skip attribute set, default to false
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parentSkip = cfg.parent.skip or false;
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# Extra step skip parameter can be string explaining the
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# skip reason.
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extraStepSkip = if builtins.isString cfg.skip then true else cfg.skip;
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# Don't run if extra step is explicitly set to skip. If
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# parameter is not set or equal to false, follow parent behavior.
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skip' = if extraStepSkip then cfg.skip else parentSkip;
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in
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if cfg.alwaysRun then false else skip';
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depends_on = lib.optional
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(buildEnabled && !cfg.alwaysRun && !cfg.needsOutput)
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cfg.parent.key;
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command = pkgs.writeShellScript "${cfg.key}-script" ''
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set -ueo pipefail
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${lib.optionalString cfg.needsOutput
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"echo '~~~ Preparing build output of ${cfg.parentLabel}'"
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}
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${lib.optionalString cfg.needsOutput cfg.parent.command}
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echo '+++ Running extra step command'
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exec ${cfg.command}
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'';
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} // (lib.optionalAttrs (cfg.agents != null) { inherit (cfg) agents; })
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// (lib.optionalAttrs (cfg.branches != null) {
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branches = lib.concatStringsSep " " cfg.branches;
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});
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in
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if (isString cfg.prompt)
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then
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mkGatedStep
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{
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inherit step;
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inherit (cfg) label parent prompt;
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}
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else step;
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}
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