primops: add builtins.convertHash

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

doc/manual/src/release-notes/rl-next.md

@@ -8,4 +8,6 @@
 
 - Introduce new flake installable syntax `flakeref#.attrPath` where the "." prefix denotes no searching of default attribute prefixes like `packages.<SYSTEM>` or `legacyPackages.<SYSTEM>`.
 
+- Introduce a new built-in function [`builtins.convertHash`](@docroot@/language/builtins.md#builtins-convertHash).
+
 - `builtins.fetchTree` is now marked as stable.

src/libexpr/primops.cc

@@ -3774,6 +3774,101 @@ static RegisterPrimOp primop_hashString({
     .fun = prim_hashString,
 });
 
+static void prim_convertHash(EvalState & state, const PosIdx pos, Value * * args, Value & v)
+{
+    state.forceAttrs(*args[0], pos, "while evaluating the first argument passed to builtins.convertHash");
+    auto &inputAttrs = args[0]->attrs;
+
+    Bindings::iterator iteratorHash = getAttr(state, state.symbols.create("hash"), inputAttrs, "while locating the attribute 'hash'");
+    auto hash = state.forceStringNoCtx(*iteratorHash->value, pos, "while evaluating the attribute 'hash'");
+
+    Bindings::iterator iteratorHashAlgo = inputAttrs->find(state.symbols.create("hashAlgo"));
+    std::optional<HashType> ht = std::nullopt;
+    if (iteratorHashAlgo != inputAttrs->end()) {
+        ht = parseHashType(state.forceStringNoCtx(*iteratorHashAlgo->value, pos, "while evaluating the attribute 'hashAlgo'"));
+    }
+
+    Bindings::iterator iteratorToHashFormat = getAttr(state, state.symbols.create("toHashFormat"), args[0]->attrs, "while locating the attribute 'toHashFormat'");
+    HashFormat hf = parseHashFormat(state.forceStringNoCtx(*iteratorToHashFormat->value, pos, "while evaluating the attribute 'toHashFormat'"));
+
+    v.mkString(Hash::parseAny(hash, ht).to_string(hf, hf == HashFormat::SRI));
+}
+
+static RegisterPrimOp primop_convertHash({
+    .name = "__convertHash",
+    .args = {"args"},
+    .doc = R"(
+      Return the specified representation of a hash string, based on the attributes presented in *args*:
+
+      - `hash`
+
+        The hash to be converted.
+        The hash format is detected automatically.
+
+      - `hashAlgo`
+
+        The algorithm used to create the hash. Must be one of
+        - `"md5"`
+        - `"sha1"`
+        - `"sha256"`
+        - `"sha512"`
+
+        The attribute may be omitted when `hash` is an [SRI hash](https://www.w3.org/TR/SRI/#the-integrity-attribute) or when the hash is prefixed with the hash algorithm name followed by a colon.
+        That `<hashAlgo>:<hashBody>` syntax is supported for backwards compatibility with existing tooling.
+
+      - `toHashFormat`
+
+        The format of the resulting hash. Must be one of
+        - `"base16"`
+        - `"base32"`
+        - `"base64"`
+        - `"sri"`
+
+      The result hash is the *toHashFormat* representation of the hash *hash*.
+
+      > **Example**
+      >
+      >   Convert a SHA256 hash in Base16 to SRI:
+      >
+      > ```nix
+      > builtins.convertHash {
+      >   hash = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
+      >   toHashFormat = "sri";
+      >   hashAlgo = "sha256";
+      > }
+      > ```
+      >
+      >     "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU="
+
+      > **Example**
+      >
+      >   Convert a SHA256 hash in SRI to Base16:
+      >
+      > ```nix
+      > builtins.convertHash {
+      >   hash = "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=";
+      >   toHashFormat = "base16";
+      > }
+      > ```
+      >
+      >     "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+
+      > **Example**
+      >
+      >   Convert a hash in the form `<hashAlgo>:<hashBody>` in Base16 to SRI:
+      >
+      > ```nix
+      > builtins.convertHash {
+      >   hash = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
+      >   toHashFormat = "sri";
+      > }
+      > ```
+      >
+      >     "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU="
+    )",
+    .fun = prim_convertHash,
+});
+
 struct RegexCache
 {
     // TODO use C++20 transparent comparison when available

tests/functional/lang/eval-okay-convertHash.exp

@@ -0,0 +1 @@
+{ hashesBase16 = [ "d41d8cd98f00b204e9800998ecf8427e" "6c69ee7f211c640419d5366cc076ae46" "bb3438fbabd460ea6dbd27d153e2233b" "da39a3ee5e6b4b0d3255bfef95601890afd80709" "cd54e8568c1b37cf1e5badb0779bcbf382212189" "6d12e10b1d331dad210e47fd25d4f260802b7e77" "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855" "900a4469df00ccbfd0c145c6d1e4b7953dd0afafadd7534e3a4019e8d38fc663" "ad0387b3bd8652f730ca46d25f9c170af0fd589f42e7f23f5a9e6412d97d7e56" "cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e" "9d0886f8c6b389398a16257bc79780fab9831c7fc11c8ab07fa732cb7b348feade382f92617c9c5305fefba0af02ab5fd39a587d330997ff5bd0db19f7666653" "21644b72aa259e5a588cd3afbafb1d4310f4889680f6c83b9d531596a5a284f34dbebff409d23bcc86aee6bad10c891606f075c6f4755cb536da27db5693f3a7" ]; hashesBase32 = [ "3y8bwfr609h3lh9ch0izcqq7fl" "26mrvc0v1nslch8r0w45zywsbc" "1v4gi57l97pmnylq6lmgxkhd5v" "143xibwh31h9bvxzalr0sjvbbvpa6ffs" "i4hj30pkrfdpgc5dbcgcydqviibfhm6d" "fxz2p030yba2bza71qhss79k3l5y24kd" "0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73" "0qy6iz9yh6a079757mxdmypx0gcmnzjd3ij5q78bzk00vxll82lh" "0mkygpci4r4yb8zz5rs2kxcgvw0a2yf5zlj6r8qgfll6pnrqf0xd" "0zdl9zrg8r3i9c1g90lgg9ip5ijzv3yhz91i0zzn3r8ap9ws784gkp9dk9j3aglhgf1amqb0pj21mh7h1nxcl18akqvvf7ggqsy30yg" "19ncrpp37dx0nzzjw4k6zaqkb9mzaq2myhgpzh5aff7qqcj5wwdxslg6ixwncm7gyq8l761gwf87fgsh2bwfyr52s53k2dkqvw8c24x" "2kz74snvckxldmmbisz9ikmy031d28cs6xfdbl6rhxx42glpyz4vww4lajrc5akklxwixl0js4g84233pxvmbykiic5m7i5m9r4nr11" ]; hashesBase64 = [ "1B2M2Y8AsgTpgAmY7PhCfg==" "bGnufyEcZAQZ1TZswHauRg==" "uzQ4+6vUYOptvSfRU+IjOw==" "2jmj7l5rSw0yVb/vlWAYkK/YBwk=" "zVToVowbN88eW62wd5vL84IhIYk=" "bRLhCx0zHa0hDkf9JdTyYIArfnc=" "47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=" "kApEad8AzL/QwUXG0eS3lT3Qr6+t11NOOkAZ6NOPxmM=" "rQOHs72GUvcwykbSX5wXCvD9WJ9C5/I/Wp5kEtl9flY=" "z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg/SpIdNs6c5H0NE8XYXysP+DGNKHfuwvY7kxvUdBeoGlODJ6+SfaPg==" "nQiG+MaziTmKFiV7x5eA+rmDHH/BHIqwf6cyy3s0j+reOC+SYXycUwX++6CvAqtf05pYfTMJl/9b0NsZ92ZmUw==" "IWRLcqolnlpYjNOvuvsdQxD0iJaA9sg7nVMVlqWihPNNvr/0CdI7zIau5rrRDIkWBvB1xvR1XLU22ifbVpPzpw==" ]; hashesSRI = [ "md5-1B2M2Y8AsgTpgAmY7PhCfg==" "md5-bGnufyEcZAQZ1TZswHauRg==" "md5-uzQ4+6vUYOptvSfRU+IjOw==" "sha1-2jmj7l5rSw0yVb/vlWAYkK/YBwk=" "sha1-zVToVowbN88eW62wd5vL84IhIYk=" "sha1-bRLhCx0zHa0hDkf9JdTyYIArfnc=" "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=" "sha256-kApEad8AzL/QwUXG0eS3lT3Qr6+t11NOOkAZ6NOPxmM=" "sha256-rQOHs72GUvcwykbSX5wXCvD9WJ9C5/I/Wp5kEtl9flY=" "sha512-z4PhNX7vuL3xVChQ1m2AB9Yg5AULVxXcg/SpIdNs6c5H0NE8XYXysP+DGNKHfuwvY7kxvUdBeoGlODJ6+SfaPg==" "sha512-nQiG+MaziTmKFiV7x5eA+rmDHH/BHIqwf6cyy3s0j+reOC+SYXycUwX++6CvAqtf05pYfTMJl/9b0NsZ92ZmUw==" "sha512-IWRLcqolnlpYjNOvuvsdQxD0iJaA9sg7nVMVlqWihPNNvr/0CdI7zIau5rrRDIkWBvB1xvR1XLU22ifbVpPzpw==" ]; }

tests/functional/lang/eval-okay-convertHash.nix

@@ -0,0 +1,31 @@
+let
+  hashAlgos = [ "md5" "md5" "md5" "sha1" "sha1" "sha1" "sha256" "sha256" "sha256" "sha512" "sha512" "sha512" ];
+  hashesBase16 = import ./eval-okay-hashstring.exp;
+  map2 = f: { fsts, snds }: if fsts == [ ] then [ ] else [ (f (builtins.head fsts) (builtins.head snds)) ] ++ map2 f { fsts = builtins.tail fsts; snds = builtins.tail snds; };
+  map2' = f: fsts: snds: map2 f { inherit fsts snds; };
+  getOutputHashes = hashes: {
+    hashesBase16 = map2' (hashAlgo: hash: builtins.convertHash { inherit hash hashAlgo; toHashFormat = "base16";}) hashAlgos hashes;
+    hashesBase32 = map2' (hashAlgo: hash: builtins.convertHash { inherit hash hashAlgo; toHashFormat = "base32";}) hashAlgos hashes;
+    hashesBase64 = map2' (hashAlgo: hash: builtins.convertHash { inherit hash hashAlgo; toHashFormat = "base64";}) hashAlgos hashes;
+    hashesSRI    = map2' (hashAlgo: hash: builtins.convertHash { inherit hash hashAlgo; toHashFormat = "sri"   ;}) hashAlgos hashes;
+  };
+  getOutputHashesColon = hashes: {
+    hashesBase16 = map2' (hashAlgo: hashBody: builtins.convertHash { hash = hashAlgo + ":" + hashBody; toHashFormat = "base16";}) hashAlgos hashes;
+    hashesBase32 = map2' (hashAlgo: hashBody: builtins.convertHash { hash = hashAlgo + ":" + hashBody; toHashFormat = "base32";}) hashAlgos hashes;
+    hashesBase64 = map2' (hashAlgo: hashBody: builtins.convertHash { hash = hashAlgo + ":" + hashBody; toHashFormat = "base64";}) hashAlgos hashes;
+    hashesSRI    = map2' (hashAlgo: hashBody: builtins.convertHash { hash = hashAlgo + ":" + hashBody; toHashFormat = "sri"   ;}) hashAlgos hashes;
+  };
+  outputHashes = getOutputHashes hashesBase16;
+in
+# map2'`
+assert map2' (s1: s2: s1 + s2) [ "a" "b" ] [ "c" "d" ] == [ "ac" "bd" ];
+# hashesBase16
+assert outputHashes.hashesBase16 == hashesBase16;
+# standard SRI hashes
+assert outputHashes.hashesSRI == (map2' (hashAlgo: hashBody: hashAlgo + "-" + hashBody) hashAlgos outputHashes.hashesBase64);
+# without prefix
+assert builtins.all (x: getOutputHashes x == outputHashes) (builtins.attrValues outputHashes);
+# colon-separated.
+# Note that colon prefix must not be applied to the standard SRI. e.g. "sha256:sha256-..." is illegal.
+assert builtins.all (x: getOutputHashesColon x == outputHashes) (with outputHashes; [ hashesBase16 hashesBase32 hashesBase64 ]);
+outputHashes