integrate impure translation with flakes

Now if dream2nix is used via flakes and impure translation is required, the user will be isntructed to `nix run ...` something to generate the missing dream-lock.

src/default.nix

@@ -186,6 +186,7 @@ let
   makeDreamLockForSource =
     {
       source,
+      translator ? null,
       translatorArgs ? {},
     }@args:
     let
@@ -201,17 +202,23 @@ let
 
       source = fetchers.fetchSource { source = sourceSpec; };
 
-      translatorsForSource = translators.translatorsForInput {
-        inputFiles = [];
-        inputDirectories = [ source ];
-      };
-
       t =
         let
-          trans = b.filter (t: t.compatible && b.elem t.type [ "pure" "ifd" ]) translatorsForSource;
+          translator = translators.findOneTranslator {
+            inherit source;
+            translatorName = args.translator or null;
+          };
+
         in
-          if trans != [] then lib.elemAt trans 0 else
-            throw "Could not find a suitable translator for input";
+          if b.elem translator.type [ "pure" "ifd" ] then
+            translator
+          else
+            throw ''
+              All comaptible translators are impure and therefore require
+              pre-processing the input before evaluation.
+              Use the CLI to add this package:
+                nix run .# -- add ...
+            '';
 
       dreamLock' = translators.translators."${t.subsystem}"."${t.type}"."${t.name}".translate
         (translatorArgs // {
@@ -359,6 +366,7 @@ let
       sourceOverrides ? oldSources: {},
       packageOverrides ? {},
       builderArgs ? {},
+      translator ? null,
       translatorArgs ? {},
     }@args:
 
@@ -369,8 +377,9 @@ let
         if ( lib.isAttrs args.source && args.source ? _generic && args.source ? _subsytem )
             || lib.hasSuffix "dream-lock.json" source then
           args.source
+        # input is a source tree -> generate the dream-lock
         else
-          makeDreamLockForSource { inherit source translatorArgs; };
+          makeDreamLockForSource { inherit source translator translatorArgs; };
 
       # parse dreamLock
       dreamLockLoaded = utils.readDreamLock { dreamLock = dreamLock'; };

src/lib.nix

@@ -84,30 +84,17 @@ let
 
       allPkgs = makeNixpkgs pkgs systems;
 
-      forAllSystems = f:
-        lib.mapAttrs f allPkgs;
+      forAllSystems = f: lib.mapAttrs f allPkgs;
 
       dream2nixFor = forAllSystems (dream2nixForSystem config);
     in
       {
-        riseAndShine = riseAndShineArgs:
-          let
-            allBuilderOutputs =
-              lib.mapAttrs
-                (system: pkgs:
-                  dream2nixFor."${system}".riseAndShine riseAndShineArgs)
-                allPkgs;
 
-            flakifiedOutputs =
-              lib.mapAttrsToList
-                (system: outputs: flakifyBuilderOutputs system outputs)
-                allBuilderOutputs;
-
-          in
-            b.foldl'
-              (allOutputs: output: lib.recursiveUpdate allOutputs output)
-              {}
-              flakifiedOutputs;
+        riseAndShine = rArgs: riseAndShineFunc
+          (
+            { inherit config pkgs systems; }
+            // rArgs
+          );
 
         apps =
           forAllSystems
@@ -121,15 +108,20 @@ let
 
       };
 
-  riseAndShine =
+  riseAndShineFunc =
     {
       pkgs ? null,
+      source,
       systems ? [],
+      translator ? null,
+      translatorArgs ? {},
       ...
     }@args:
     let
 
-      argsForward = b.removeAttrs args [ "pkgs" "systems" ];
+      config = args.config or ((import ./utils/config.nix).loadConfig {});
+
+      argsForward = b.removeAttrs args [ "config" "pkgs" "systems" ];
 
       allPkgs = makeNixpkgs pkgs systems;
 
@@ -139,21 +131,64 @@ let
       allBuilderOutputs =
         lib.mapAttrs
           (system: pkgs:
-            dream2nixFor."${system}".riseAndShine argsForward)
+            let
+              dream2nix = dream2nixFor."${system}";
+
+              translatorFound = dream2nix.translators.findOneTranslator {
+                inherit source;
+                translatorName = args.translator or null;
+              };
+
+              result = translator:
+                dream2nix.riseAndShine (argsForward // {
+                  # TODO: this triggers the translator finding routine a second time
+                  translator = translatorFound.name;
+                });
+            in
+              if b.elem translatorFound.type [ "pure" "ifd" ] then
+                result translatorFound
+              else
+                b.trace ''
+                  Some information is missing to build this project reproducibly.
+                  Please execute nix run .#resolve to resolve impurities.
+                ''
+                {})
+
           allPkgs;
 
-      flakifiedOutputs =
+      flakifiedOutputsList =
         lib.mapAttrsToList
           (system: outputs: flakifyBuilderOutputs system outputs)
           allBuilderOutputs;
 
+      flakeOutputs =
+        b.foldl'
+          (allOutputs: output: lib.recursiveUpdate allOutputs output)
+          {}
+          flakifiedOutputsList;
+
+      forAllSystems = f: b.mapAttrs f allPkgs;
+
     in
-      b.foldl'
-        (allOutputs: output: lib.recursiveUpdate allOutputs output)
-        {}
-        flakifiedOutputs;
+      lib.recursiveUpdate
+        flakeOutputs
+        {
+          apps = forAllSystems (system: pkgs: {
+            resolve.type = "app";
+            resolve.program =
+              let
+                utils = (dream2nixFor."${system}".utils);
+              in
+                b.toString
+                  (utils.makePackageLockScript {
+                    inherit source translator translatorArgs;
+                    packagesDir = config.packagesDir;
+                  });
+          });
+        };
 
 in
 {
-  inherit init riseAndShine;
+  inherit init;
+  riseAndShine = riseAndShineFunc;
 }

src/translators/default.nix

@@ -92,8 +92,23 @@ let
     )
   );
 
-  # flat list of all translators
-  translatorsList = lib.collect (v: v ? translateBin) translators;
+  # flat list of all translators sorted by priority (pure translators first)
+  translatorsList =
+    let
+      list = lib.collect (v: v ? translateBin) translators;
+      prio = translator:
+        if translator.type == "pure" then
+          0
+        else if translator.type == "ifd" then
+          1
+        else if translator.type == "impure" then
+          2
+        else
+          3;
+    in
+      b.sort
+        (a: b: (prio a) < (prio b))
+        list;
 
   # returns the list of translators including their special args
   # and adds a flag `compatible` to each translator indicating
@@ -170,9 +185,50 @@ let
       )
       extraArgsDef;
 
+
+  # return one compatible translator or throw error
+  findOneTranslator =
+    {
+      source,
+      translatorName ? null,
+    }@args:
+    let
+      translatorsForSource = translatorsForInput {
+        inputFiles = [];
+        inputDirectories = [ source ];
+      };
+
+      nameFilter =
+        if translatorName != null then
+          (translator: translator.name == translatorName)
+        else
+          (translator: true);
+
+      compatibleTranslators =
+        let
+          result =
+            b.filter
+              (t: t.compatible)
+              translatorsForSource;
+        in
+          if result == [] then
+            throw "Could not find a compatible translator for input"
+          else
+            result;
+
+      translator =
+        lib.findFirst
+          nameFilter
+          (throw ''Specified translator ${translatorName} not found or incompatible'')
+          compatibleTranslators;
+
+    in
+      translator;
+
 in
 {
   inherit
+    findOneTranslator
     translators
     translatorsForInput
     translatorsForInputRecursive

src/utils/default.nix

@@ -10,6 +10,7 @@
   writeScript,
 
   # dream2nix inputs
+  apps,
   callPackageDream,
   externalSources,
   ...
@@ -128,6 +129,7 @@ rec {
 
     export PATH="${lib.makeBinPath availablePrograms}"
     export NIX_PATH=nixpkgs=${pkgs.path}
+    export WORKDIR="$PWD"
 
     tmpdir=$(${coreutils}/bin/mktemp -d)
     cd $tmpdir
@@ -192,8 +194,28 @@ rec {
 
   satisfiesSemver = poetry2nixSemver.satisfiesSemver;
 
-  # like nixpkgs recursiveUpdateUntil, but the depth of the
+  # like nixpkgs recursiveUpdateUntil, but with the depth as a stop condition
   recursiveUpdateUntilDepth = depth: lhs: rhs:
     lib.recursiveUpdateUntil (path: l: r: (b.length path) > depth) lhs rhs;
 
+
+  # a script that produces and dumps the dream-lock json for a given source
+  makePackageLockScript =
+    {
+      packagesDir,
+      source,
+      translator,
+      translatorArgs,
+    }:
+    writePureShellScript
+      []
+      ''
+        ${apps.cli.program} add ${source} \
+          --translator ${translator} \
+          --packages-root $WORKDIR/${packagesDir} \
+          ${lib.concatStringsSep " \\\n"
+            (lib.mapAttrsToList
+              (key: val: "--arg ${key}=${val}")
+              translatorArgs)}
+      '';
 }