From 2d1d81114d72ace89ce08cd3bc93f4eb27a2975d Mon Sep 17 00:00:00 2001 From: Alex Ameen Date: Tue, 25 Jul 2023 12:43:33 -0500 Subject: [PATCH] Add `parseFlakeRef` and `flakeRefToString` builtins (#8670) Over the last year or so I've run into several use cases where I need to parse and/or serialize URLs for use by `builtins.fetchTree` or `builtins.getFlake`, largely in order to produce _lockfile-like_ files for lang2nix frameworks or tools which use `nix` internally to drive builds. I've gone through the painstaking process of emulating `nix::FlakeRef::fromAttrs` and `nix::parseFlakeRef` several times with mixed success; but these are difficult to create and even harder to maintain if I hope to stay aligned with changes to the real parser/serializer. I understand why adding new `builtins` isn't something we want to do flagrantly. I'm recommending this addition simply because I keep encountering use cases where I need to parse/serialize these URIs in `nix` expressions, and I want a reliable solution. Co-authored-by: Eelco Dolstra Co-authored-by: John Ericson --- doc/manual/src/release-notes/rl-next.md | 7 ++ src/libexpr/flake/flake.cc | 95 ++++++++++++++++++++ tests/lang/eval-okay-flake-ref-to-string.exp | 1 + tests/lang/eval-okay-flake-ref-to-string.nix | 7 ++ tests/lang/eval-okay-parse-flake-ref.exp | 1 + tests/lang/eval-okay-parse-flake-ref.nix | 1 + 6 files changed, 112 insertions(+) create mode 100644 tests/lang/eval-okay-flake-ref-to-string.exp create mode 100644 tests/lang/eval-okay-flake-ref-to-string.nix create mode 100644 tests/lang/eval-okay-parse-flake-ref.exp create mode 100644 tests/lang/eval-okay-parse-flake-ref.nix diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md index c869b5e2f..065364453 100644 --- a/doc/manual/src/release-notes/rl-next.md +++ b/doc/manual/src/release-notes/rl-next.md @@ -1 +1,8 @@ # Release X.Y (202?-??-??) + +- Two new builtin functions, + [`builtins.parseFlakeRef`](@docroot@/language/builtins.md#builtins-parseFlakeRef) + and + [`builtins.flakeRefToString`](@docroot@/language/builtins.md#builtins-flakeRefToString), + have been added. + These functions are useful for converting between flake references encoded as attribute sets and URLs. diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc index 5aa44d6a1..9112becff 100644 --- a/src/libexpr/flake/flake.cc +++ b/src/libexpr/flake/flake.cc @@ -793,6 +793,101 @@ static RegisterPrimOp r2({ .experimentalFeature = Xp::Flakes, }); +static void prim_parseFlakeRef( + EvalState & state, + const PosIdx pos, + Value * * args, + Value & v) +{ + std::string flakeRefS(state.forceStringNoCtx(*args[0], pos, + "while evaluating the argument passed to builtins.parseFlakeRef")); + auto attrs = parseFlakeRef(flakeRefS, {}, true).toAttrs(); + auto binds = state.buildBindings(attrs.size()); + for (const auto & [key, value] : attrs) { + auto s = state.symbols.create(key); + auto & vv = binds.alloc(s); + std::visit(overloaded { + [&vv](const std::string & value) { vv.mkString(value); }, + [&vv](const uint64_t & value) { vv.mkInt(value); }, + [&vv](const Explicit & value) { vv.mkBool(value.t); } + }, value); + } + v.mkAttrs(binds); +} + +static RegisterPrimOp r3({ + .name = "__parseFlakeRef", + .args = {"flake-ref"}, + .doc = R"( + Parse a flake reference, and return its exploded form. + + For example: + ```nix + builtins.parseFlakeRef "github:NixOS/nixpkgs/23.05?dir=lib" + ``` + evaluates to: + ```nix + { dir = "lib"; owner = "NixOS"; ref = "23.05"; repo = "nixpkgs"; type = "github"; } + ``` + )", + .fun = prim_parseFlakeRef, + .experimentalFeature = Xp::Flakes, +}); + + +static void prim_flakeRefToString( + EvalState & state, + const PosIdx pos, + Value * * args, + Value & v) +{ + state.forceAttrs(*args[0], noPos, + "while evaluating the argument passed to builtins.flakeRefToString"); + fetchers::Attrs attrs; + for (const auto & attr : *args[0]->attrs) { + auto t = attr.value->type(); + if (t == nInt) { + attrs.emplace(state.symbols[attr.name], + (uint64_t) attr.value->integer); + } else if (t == nBool) { + attrs.emplace(state.symbols[attr.name], + Explicit { attr.value->boolean }); + } else if (t == nString) { + attrs.emplace(state.symbols[attr.name], + std::string(attr.value->str())); + } else { + state.error( + "flake reference attribute sets may only contain integers, Booleans, " + "and strings, but attribute '%s' is %s", + state.symbols[attr.name], + showType(*attr.value)).debugThrow(); + } + } + auto flakeRef = FlakeRef::fromAttrs(attrs); + v.mkString(flakeRef.to_string()); +} + +static RegisterPrimOp r4({ + .name = "__flakeRefToString", + .args = {"attrs"}, + .doc = R"( + Convert a flake reference from attribute set format to URL format. + + For example: + ```nix + builtins.flakeRefToString { + dir = "lib"; owner = "NixOS"; ref = "23.05"; repo = "nixpkgs"; type = "github"; + } + ``` + evaluates to + ```nix + "github:NixOS/nixpkgs/23.05?dir=lib" + ``` + )", + .fun = prim_flakeRefToString, + .experimentalFeature = Xp::Flakes, +}); + } Fingerprint LockedFlake::getFingerprint() const diff --git a/tests/lang/eval-okay-flake-ref-to-string.exp b/tests/lang/eval-okay-flake-ref-to-string.exp new file mode 100644 index 000000000..110f8442d --- /dev/null +++ b/tests/lang/eval-okay-flake-ref-to-string.exp @@ -0,0 +1 @@ +"github:NixOS/nixpkgs/23.05?dir=lib" diff --git a/tests/lang/eval-okay-flake-ref-to-string.nix b/tests/lang/eval-okay-flake-ref-to-string.nix new file mode 100644 index 000000000..dbb4e5b2a --- /dev/null +++ b/tests/lang/eval-okay-flake-ref-to-string.nix @@ -0,0 +1,7 @@ +builtins.flakeRefToString { + type = "github"; + owner = "NixOS"; + repo = "nixpkgs"; + ref = "23.05"; + dir = "lib"; +} diff --git a/tests/lang/eval-okay-parse-flake-ref.exp b/tests/lang/eval-okay-parse-flake-ref.exp new file mode 100644 index 000000000..fc17ba085 --- /dev/null +++ b/tests/lang/eval-okay-parse-flake-ref.exp @@ -0,0 +1 @@ +{ dir = "lib"; owner = "NixOS"; ref = "23.05"; repo = "nixpkgs"; type = "github"; } diff --git a/tests/lang/eval-okay-parse-flake-ref.nix b/tests/lang/eval-okay-parse-flake-ref.nix new file mode 100644 index 000000000..db4ed2742 --- /dev/null +++ b/tests/lang/eval-okay-parse-flake-ref.nix @@ -0,0 +1 @@ + builtins.parseFlakeRef "github:NixOS/nixpkgs/23.05?dir=lib"