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https://github.com/NixOS/nix
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929423476e
This is useful for frameworks (such as flake-parts) to avoid unnecessary evaluation. See discussion here: https://github.com/hercules-ci/flake-parts/issues/288#issuecomment-2912459614 While digging into this, I discovered that `nix fmt` already handles `null` formatters identically to undefined formatters. I added a couple of tests to demonstrate this behavior. `nix flake show` needs some reworking to avoid crashing with a "error: expected a derivation" when it encounters a `null` formatter or package. My changes here avoid the crash, but has some cosmetic issues, which is why I've labeled this PR as a draft. Cosmetic issues =============== With the following `flake.nix`: ```nix { outputs = _: { packages.x86_64-linux.default = null; }; } ``` `nix flake show` shows a weird empty system: ``` $ nix flake show path:/tmp/tmp.uL0iGuNwXB?lastModified=1748472558&narHash=sha256-tC%2BhdXAyoeFvWHNllJbois8X%2B7wpZ6CJzEzbcaGQxtM%3D └───packages └───x86_64-linux ``` Similarly, `nix flake show --json` includes an empty object: ``` $ nix flake show --json { "packages": { "x86_64-linux": { "default": null } } } ``` `nix build` crashes: ``` $ nix build .#default error: expected flake output attribute 'packages.x86_64-linux.default' to be a derivation or path but found null: null ```
104 lines
2.9 KiB
Bash
Executable file
104 lines
2.9 KiB
Bash
Executable file
#!/usr/bin/env bash
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source ./common.sh
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flakeDir=$TEST_ROOT/flake
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mkdir -p "$flakeDir"
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writeSimpleFlake "$flakeDir"
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pushd "$flakeDir"
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# By default: Only show the packages content for the current system and no
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# legacyPackages at all
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nix flake show --json > show-output.json
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nix eval --impure --expr '
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let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
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in
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assert show_output.packages.someOtherSystem.default == {};
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assert show_output.packages.${builtins.currentSystem}.default.name == "simple";
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assert show_output.legacyPackages.${builtins.currentSystem} == {};
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true
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'
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# With `--all-systems`, show the packages for all systems
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nix flake show --json --all-systems > show-output.json
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nix eval --impure --expr '
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let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
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in
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assert show_output.packages.someOtherSystem.default.name == "simple";
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assert show_output.legacyPackages.${builtins.currentSystem} == {};
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true
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'
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# With `--legacy`, show the legacy packages
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nix flake show --json --legacy > show-output.json
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nix eval --impure --expr '
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let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
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in
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assert show_output.legacyPackages.${builtins.currentSystem}.hello.name == "simple";
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true
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'
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# Test that attributes are only reported when they have actual content
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cat >flake.nix <<EOF
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{
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description = "Bla bla";
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outputs = inputs: rec {
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apps.$system = { };
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checks.$system = { };
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devShells.$system = { };
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legacyPackages.$system = { };
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packages.$system = { };
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packages.someOtherSystem = { };
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formatter.x86_64-linux = null;
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nixosConfigurations = { };
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nixosModules = { };
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};
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}
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EOF
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nix flake show --json --all-systems > show-output.json
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nix eval --impure --expr '
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let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
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in
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assert show_output == { formatter = { x86_64-linux = null; }; };
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true
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'
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# Test that attributes with errors are handled correctly.
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# nixpkgs.legacyPackages is a particularly prominent instance of this.
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cat >flake.nix <<EOF
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{
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outputs = inputs: {
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legacyPackages.$system = {
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AAAAAASomeThingsFailToEvaluate = throw "nooo";
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simple = import ./simple.nix;
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};
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};
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}
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EOF
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nix flake show --json --legacy --all-systems > show-output.json
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nix eval --impure --expr '
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let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
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in
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assert show_output.legacyPackages.${builtins.currentSystem}.AAAAAASomeThingsFailToEvaluate == { };
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assert show_output.legacyPackages.${builtins.currentSystem}.simple.name == "simple";
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true
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'
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# Test that nix flake show doesn't fail if one of the outputs contains
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# an IFD
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popd
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writeIfdFlake $flakeDir
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pushd $flakeDir
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nix flake show --json > show-output.json
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nix eval --impure --expr '
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let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
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in
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assert show_output.packages.${builtins.currentSystem}.default == { };
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true
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'
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