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nixos/bazelisk: add NixOS module
Add a programs.bazelisk NixOS module that installs bazelisk with a bazel symlink, enables envfs for /bin/bash compatibility, and writes /etc/bazel.bazelrc with Nix store paths for common Bazel action tools. The module also supports optional CC/CXX settings for rules_cc detection, extra action PATH packages, and extra bazelrc lines. Add a NixOS test covering the generated bazelrc, envfs fallback, and bazel symlink, and link it from bazelisk.passthru.tests.
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‎nixos/modules/module-list.nix‎

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./programs/bash/undistract-me.nix
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./programs/bat.nix
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./programs/bazecor.nix
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./programs/bazelisk.nix
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./programs/bcc.nix
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./programs/benchexec.nix
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./programs/browserpass.nix

‎nixos/modules/programs/bazelisk.md‎

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# Bazelisk {#module-programs-bazelisk}
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The `programs.bazelisk` module installs Bazelisk as both `bazelisk` and
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`bazel`, enables envfs so unpatched Bazel binaries can resolve `/bin/bash`,
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and writes `/etc/bazel.bazelrc` with Nix store paths for common action tools.
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Set `programs.bazelisk.cc` and `programs.bazelisk.cxx` when a project needs C
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or C++ toolchain detection through `rules_cc`.

‎nixos/modules/programs/bazelisk.nix‎

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{
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config,
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lib,
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pkgs,
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...
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}:
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let
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cfg = config.programs.bazelisk;
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# Build a PATH containing common tools that Bazel actions need.
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defaultActionPath = lib.makeBinPath (
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with pkgs;
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[
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bash
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binutils
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coreutils
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findutils
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gawk
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gnugrep
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gnused
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gnutar
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gzip
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which
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unzip
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]
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++ cfg.extraPackages
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);
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bazelrc = pkgs.writeText "bazel.bazelrc" ''
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# Generated by NixOS programs.bazelisk module.
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# NixOS needs an explicit PATH for Bazel actions since tools live in the
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# Nix store and are not at standard FHS locations.
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build --action_env=PATH=${defaultActionPath}
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build --host_action_env=PATH=${defaultActionPath}
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${lib.optionalString (cfg.cc != null) ''
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build --repo_env=CC=${cfg.cc}
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build --action_env=CC=${cfg.cc}
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''}
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${lib.optionalString (cfg.cxx != null) ''
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build --repo_env=CXX=${cfg.cxx}
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build --action_env=CXX=${cfg.cxx}
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''}
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${cfg.extraBazelrc}
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'';
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in
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{
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options.programs.bazelisk = {
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enable = lib.mkEnableOption ''
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bazelisk, a version-switching launcher for Bazel.
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Enabling this module installs bazelisk with a `bazel` symlink, enables
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envfs (so unpatched Bazel binaries can find `/bin/bash`), and writes a
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system-wide `/etc/bazel.bazelrc` that sets `--action_env=PATH` and
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`--host_action_env=PATH` to Nix store paths for common tools.
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Per-project settings (e.g. extra rustc flags, pkg-config paths) still
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belong in `.bazelrc.user`
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'';
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package = lib.mkPackageOption pkgs "bazelisk" { };
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cc = lib.mkOption {
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type = lib.types.nullOr lib.types.str;
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default = null;
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example = lib.literalExpression ''"''${pkgs.clang}/bin/clang"'';
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description = ''
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Path to the C compiler. Set via `--repo_env=CC` and `--action_env=CC`
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in the system bazelrc so that rules_cc toolchain detection works.
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'';
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};
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cxx = lib.mkOption {
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type = lib.types.nullOr lib.types.str;
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default = null;
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example = lib.literalExpression ''"''${pkgs.clang}/bin/clang++"'';
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description = ''
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Path to the C++ compiler. Set via `--repo_env=CXX` and `--action_env=CXX`
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in the system bazelrc so that rules_cc toolchain detection works.
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'';
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};
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extraPackages = lib.mkOption {
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type = lib.types.listOf lib.types.package;
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default = [ ];
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description = ''
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Additional packages to include in the Bazel action PATH.
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'';
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};
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extraBazelrc = lib.mkOption {
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type = lib.types.lines;
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default = "";
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description = ''
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Extra lines appended to the system `/etc/bazel.bazelrc`.
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'';
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};
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};
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config = lib.mkIf cfg.enable {
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# Install bazelisk with a `bazel` symlink so it's a drop-in replacement.
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environment.systemPackages = [
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(pkgs.symlinkJoin {
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name = "bazelisk-with-bazel";
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paths = [ cfg.package ];
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postBuild = "ln -sf $out/bin/bazelisk $out/bin/bazel";
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})
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];
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# envfs provides /bin/bash and /usr/bin/env for unpatched Bazel binaries.
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services.envfs.enable = true;
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services.envfs.extraFallbackPathCommands = ''
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ln -s ${pkgs.bash}/bin/bash $out/bash
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'';
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# System-wide bazelrc with NixOS-compatible defaults.
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environment.etc."bazel.bazelrc".source = bazelrc;
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};
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meta = {
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doc = ./bazelisk.md;
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maintainers = with lib.maintainers; [ dhashs ];
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};
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}

‎nixos/tests/all-tests.nix‎

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ayatana-indicators = runTest ./ayatana-indicators.nix;
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babeld = runTest ./babeld.nix;
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bazarr = runTest ./bazarr.nix;
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bazelisk = runTest ./bazelisk.nix;
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bcache = runTestOn [ "x86_64-linux" "aarch64-linux" ] ./bcache.nix;
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bcachefs = runTestOn [ "x86_64-linux" "aarch64-linux" ] ./bcachefs.nix;
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beanstalkd = runTest ./beanstalkd.nix;

‎nixos/tests/bazelisk.nix‎

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{
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pkgs,
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...
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}:
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let
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fakeBazelisk = pkgs.writeShellScriptBin "bazelisk" ''
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echo "fake bazelisk $*"
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'';
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fakeCc = pkgs.writeShellScriptBin "bazelisk-test-cc" ''
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exit 0
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'';
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fakeCxx = pkgs.writeShellScriptBin "bazelisk-test-cxx" ''
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exit 0
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'';
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extraTool = pkgs.writeShellScriptBin "bazelisk-extra-tool" ''
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echo "extra tool"
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'';
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in
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{
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name = "bazelisk";
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nodes.machine = {
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programs.bazelisk = {
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enable = true;
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package = fakeBazelisk;
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cc = "${fakeCc}/bin/bazelisk-test-cc";
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cxx = "${fakeCxx}/bin/bazelisk-test-cxx";
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extraPackages = [ extraTool ];
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extraBazelrc = ''
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build --action_env=BAZELISK_TEST=1
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'';
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};
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};
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testScript = ''
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start_all()
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machine.wait_until_succeeds("mountpoint -q /usr/bin")
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machine.wait_until_succeeds("test -e /bin/bash")
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machine.succeed("test -x /run/current-system/sw/bin/bazelisk")
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machine.succeed("test -x /run/current-system/sw/bin/bazel")
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machine.succeed("bazel --version | grep 'fake bazelisk --version'")
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machine.succeed("PATH= /bin/bash --version")
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bazelrc = machine.succeed("cat /etc/bazel.bazelrc")
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for expected in [
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"build --action_env=PATH=",
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"build --host_action_env=PATH=",
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"${pkgs.bash}/bin",
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"${pkgs.binutils}/bin",
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"${pkgs.coreutils}/bin",
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"${extraTool}/bin",
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"build --repo_env=CC=${fakeCc}/bin/bazelisk-test-cc",
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"build --action_env=CC=${fakeCc}/bin/bazelisk-test-cc",
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"build --repo_env=CXX=${fakeCxx}/bin/bazelisk-test-cxx",
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"build --action_env=CXX=${fakeCxx}/bin/bazelisk-test-cxx",
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"build --action_env=BAZELISK_TEST=1",
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]:
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assert expected in bazelrc, f"{expected!r} missing from bazelrc"
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'';
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}

‎pkgs/by-name/ba/bazelisk/package.nix‎

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lib,
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buildGoModule,
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fetchFromGitHub,
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nixosTests,
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}:
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buildGoModule (finalAttrs: {
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"-X github.com/bazelbuild/bazelisk/core.BazeliskVersion=v${finalAttrs.version}"
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];
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passthru.tests = {
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inherit (nixosTests) bazelisk;
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};
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meta = {
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description = "User-friendly launcher for Bazel";
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mainProgram = "bazelisk";
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longDescription = ''
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BEWARE: This package does not work on NixOS.
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A user-friendly launcher for Bazel that automatically downloads and
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runs the correct Bazel version for a given project.
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On NixOS, enable the `programs.bazelisk` module to set up envfs and
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a system bazelrc with the correct tool paths.
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'';
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homepage = "https://github.com/bazelbuild/bazelisk";
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changelog = "https://github.com/bazelbuild/bazelisk/releases/tag/v${finalAttrs.version}";

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