lib/meta: add getLicenseFromSpdxId function

Move function spdxLicense, internally used in yarn2nix
to lib/meta.nix, and
rename to getLicenseFromSpdxId

A similar function is implemented in poetry2nix,
but the one originally in yarn2nix seems beter.
since it falls back to an license-like attrset
for mismatched case
instead of a plain string

lib/default.nix

@@ -105,7 +105,7 @@ let
       makeScope makeScopeWithSplicing;
     inherit (self.meta) addMetaAttrs dontDistribute setName updateName
       appendToName mapDerivationAttrset setPrio lowPrio lowPrioSet hiPrio
-      hiPrioSet;
+      hiPrioSet getLicenseFromSpdxId;
     inherit (self.sources) pathType pathIsDirectory cleanSourceFilter
       cleanSource sourceByRegex sourceFilesBySuffices
       commitIdFromGitRepo cleanSourceWith pathHasContext

lib/meta.nix

@@ -99,4 +99,31 @@ rec {
   availableOn = platform: pkg:
     lib.any (platformMatch platform) pkg.meta.platforms &&
     lib.all (elem: !platformMatch platform elem) (pkg.meta.badPlatforms or []);
+
+  /* Get the corresponding attribute in lib.licenses
+     from the SPDX ID.
+     For SPDX IDs, see
+     https://spdx.org/licenses
+
+     Type:
+       getLicenseFromSpdxId :: str -> AttrSet
+
+     Example:
+       lib.getLicenseFromSpdxId "MIT" == lib.licenses.mit
+       => true
+       lib.getLicenseFromSpdxId "mIt" == lib.licenses.mit
+       => true
+       lib.getLicenseFromSpdxId "MY LICENSE"
+       => trace: warning: getLicenseFromSpdxId: No license matches the given SPDX ID: MY LICENSE
+       => { shortName = "MY LICENSE"; }
+  */
+  getLicenseFromSpdxId =
+    let
+      spdxLicenses = lib.mapAttrs (id: ls: assert lib.length ls == 1; builtins.head ls)
+        (lib.groupBy (l: lib.toLower l.spdxId) (lib.filter (l: l ? spdxId) (lib.attrValues lib.licenses)));
+    in licstr:
+      spdxLicenses.${ lib.toLower licstr } or (
+        lib.warn "getLicenseFromSpdxId: No license matches the given SPDX ID: ${licstr}"
+        { shortName = licstr; }
+      );
 }

pkgs/development/tools/yarn2nix-moretea/yarn2nix/default.nix

@@ -1,6 +1,7 @@
 { pkgs ? import <nixpkgs> {}
 , nodejs ? pkgs.nodejs
 , yarn ? pkgs.yarn
+, allowAliases ? pkgs.config.allowAliases or true
 }:
 
 let
@@ -9,6 +10,14 @@ let
   compose = f: g: x: f (g x);
   id = x: x;
   composeAll = builtins.foldl' compose id;
+
+  # https://docs.npmjs.com/files/package.json#license
+  # TODO: support expression syntax (OR, AND, etc)
+  getLicenseFromSpdxId = licstr:
+    if licstr == "UNLICENSED" then
+      lib.licenses.unfree
+    else
+      lib.getLicenseFromSpdxId licstr;
 in rec {
   # Export yarn again to make it easier to find out which yarn was used.
   inherit yarn;
@@ -30,16 +39,7 @@ in rec {
       non-null = builtins.filter (x: x != null) parts;
     in builtins.concatStringsSep "-" non-null;
 
-  # https://docs.npmjs.com/files/package.json#license
-  # TODO: support expression syntax (OR, AND, etc)
-  spdxLicense = licstr:
-    if licstr == "UNLICENSED" then
-      lib.licenses.unfree
-    else
-      lib.findFirst
-        (l: l ? spdxId && l.spdxId == licstr)
-        { shortName = licstr; }
-        (builtins.attrValues lib.licenses);
+  inherit getLicenseFromSpdxId;
 
   # Generates the yarn.nix from the yarn.lock file
   mkYarnNix = { yarnLock, flags ? [] }:
@@ -369,7 +369,7 @@ in rec {
         description = packageJSON.description or "";
         homepage = packageJSON.homepage or "";
         version = packageJSON.version or "";
-        license = if packageJSON ? license then spdxLicense packageJSON.license else "";
+        license = if packageJSON ? license then getLicenseFromSpdxId packageJSON.license else "";
       } // (attrs.meta or {});
     });
 
@@ -437,4 +437,7 @@ in rec {
 
     patchShebangs $out
   '';
+} // lib.optionalAttrs allowAliases {
+  # Aliases
+  spdxLicense = getLicenseFromSpdxId; # added 2021-12-01
 }