add nix-store --query --valid-derivers command

notably useful when nix-store --query --deriver returns a non-existing
path.

Co-authored-by: Felix Uhl <iFreilicht@users.noreply.github.com>

doc/manual/src/command-ref/nix-store/query.md

@@ -5,8 +5,8 @@
 # Synopsis
 
 `nix-store` {`--query` | `-q`}
-  {`--outputs` | `--requisites` | `-R` | `--references` |
+  {`--outputs` | `--requisites` | `-R` | `--references` | `--referrers` |
-  `--referrers` | `--referrers-closure` | `--deriver` | `-d` |
+  `--referrers-closure` | `--deriver` | `-d` | `--valid-derivers` |
   `--graph` | `--tree` | `--binding` *name* | `-b` *name* | `--hash` |
   `--size` | `--roots`}
   [`--use-output`] [`-u`] [`--force-realise`] [`-f`]
@@ -82,13 +82,21 @@ symlink.
     in the Nix store that are dependent on *paths*.
 
   - `--deriver`; `-d`\
-    Prints the [deriver] of the store paths *paths*. If
+    Prints the [deriver] that was used to build the store paths *paths*. If
     the path has no deriver (e.g., if it is a source file), or if the
     deriver is not known (e.g., in the case of a binary-only
     deployment), the string `unknown-deriver` is printed.
+    The returned deriver is not guaranteed to exist in the local store, for
+    example when *paths* were substituted from a binary cache.
+    Use `--valid-derivers` instead to obtain valid paths only.
 
     [deriver]: ../../glossary.md#gloss-deriver
 
+  - `--valid-derivers`\
+    Prints a set of derivation files (`.drv`) which are supposed produce
+    said paths when realized. Might print nothing, for example for source paths
+    or paths subsituted from a binary cache.
+
   - `--graph`\
     Prints the references graph of the store paths *paths* in the format
     of the `dot` tool of AT\&T's [Graphviz

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

@@ -22,3 +22,7 @@
 
 - Introduce a new [`outputOf`](@docroot@/language/builtins.md#builtins-outputOf) builtin.
   It is part of the [`dynamic-derivations`](@docroot@/contributing/experimental-features.md#xp-feature-dynamic-derivations) experimental feature.
+
+- [`nix-store --query`](@docroot@/command-ref/nix-store/query.md) gained a new type of query: `--valid-derivers`. It returns all `.drv` files in the local store that *can be* used to build the output passed in argument.
+This is in contrast to `--deriver`, which returns the single `.drv` file that *was actually* used to build the output passed in argument. In case the output was substituted from a binary cache,
+this `.drv` file may only exist on said binary cache and not locally.

src/nix-store/nix-store.cc

@@ -283,7 +283,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
 {
     enum QueryType
         { qOutputs, qRequisites, qReferences, qReferrers
-        , qReferrersClosure, qDeriver, qBinding, qHash, qSize
+        , qReferrersClosure, qDeriver, qValidDerivers, qBinding, qHash, qSize
         , qTree, qGraph, qGraphML, qResolve, qRoots };
     std::optional<QueryType> query;
     bool useOutput = false;
@@ -299,6 +299,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
         else if (i == "--referrers" || i == "--referers") query = qReferrers;
         else if (i == "--referrers-closure" || i == "--referers-closure") query = qReferrersClosure;
         else if (i == "--deriver" || i == "-d") query = qDeriver;
+        else if (i == "--valid-derivers") query = qValidDerivers;
         else if (i == "--binding" || i == "-b") {
             if (opArgs.size() == 0)
                 throw UsageError("expected binding name");
@@ -372,6 +373,21 @@ static void opQuery(Strings opFlags, Strings opArgs)
             }
             break;
 
+        case qValidDerivers: {
+            StorePathSet result;
+            for (auto & i : opArgs) {
+                auto derivers = store->queryValidDerivers(store->followLinksToStorePath(i));
+                for (const auto &i: derivers) {
+                    result.insert(i);
+                }
+            }
+            auto sorted = store->topoSortPaths(result);
+            for (StorePaths::reverse_iterator i = sorted.rbegin();
+                 i != sorted.rend(); ++i)
+                cout << fmt("%s\n", store->printStorePath(*i));
+            break;
+        }
+
         case qBinding:
             for (auto & i : opArgs) {
                 auto path = useDeriver(store->followLinksToStorePath(i));

tests/check-refs.nix

@@ -2,7 +2,7 @@ with import ./config.nix;
 
 rec {
 
-  dep = import ./dependencies.nix;
+  dep = import ./dependencies.nix {};
 
   makeTest = nr: args: mkDerivation ({
     name = "check-refs-" + toString nr;

tests/dependencies.nix

@@ -1,3 +1,4 @@
+{ hashInvalidator ? "" }:
 with import ./config.nix;
 
 let {
@@ -21,6 +22,17 @@ let {
     '';
   };
 
+  fod_input = mkDerivation {
+    name = "fod-input";
+    buildCommand = ''
+      echo ${hashInvalidator}
+      echo FOD > $out
+    '';
+    outputHashMode = "flat";
+    outputHashAlgo = "sha256";
+    outputHash = "1dq9p0hnm1y75q2x40fws5887bq1r840hzdxak0a9djbwvx0b16d";
+  };
+
   body = mkDerivation {
     name = "dependencies-top";
     builder = ./dependencies.builder0.sh + "/FOOBAR/../.";
@@ -29,6 +41,7 @@ let {
     input1_drv = input1;
     input2_drv = input2;
     input0_drv = input0;
+    fod_input_drv = fod_input;
     meta.description = "Random test package";
   };
 

tests/dependencies.sh

@@ -53,3 +53,20 @@ nix-store -q --referrers-closure "$input2OutPath" | grep "$outPath"
 # Check that the derivers are set properly.
 test $(nix-store -q --deriver "$outPath") = "$drvPath"
 nix-store -q --deriver "$input2OutPath" | grepQuiet -- "-input-2.drv"
+
+# --valid-derivers returns the currently single valid .drv file
+test "$(nix-store -q --valid-derivers "$outPath")" = "$drvPath"
+
+# instantiate a different drv with the same output
+drvPath2=$(nix-instantiate dependencies.nix --argstr hashInvalidator yay)
+
+# now --valid-derivers returns both
+test "$(nix-store -q --valid-derivers "$outPath" | sort)" = "$(sort <<< "$drvPath"$'\n'"$drvPath2")"
+
+# check that nix-store --valid-derivers only returns existing drv
+nix-store --delete "$drvPath"
+test "$(nix-store -q --valid-derivers "$outPath")" = "$drvPath2"
+
+# check that --valid-derivers returns nothing when there are no valid derivers
+nix-store --delete "$drvPath2"
+test -z "$(nix-store -q --valid-derivers "$outPath")"

tests/dyn-drv/eval-outputOf.sh

@@ -13,14 +13,14 @@ nix --experimental-features 'nix-command' eval --impure  --expr \
 # the future so it does work, but there are some design questions to
 # resolve first. Adding a test so we don't liberalise it by accident.
 expectStderr 1 nix --experimental-features 'nix-command dynamic-derivations' eval --impure --expr \
-    'builtins.outputOf (import ../dependencies.nix) "out"' \
+    'builtins.outputOf (import ../dependencies.nix {}) "out"' \
     | grepQuiet "value is a set while a string was expected"
 
 # Test that "DrvDeep" string contexts are not supported at this time
 #
 # Like the above, this is a restriction we could relax later.
 expectStderr 1 nix --experimental-features 'nix-command dynamic-derivations' eval --impure --expr \
-    'builtins.outputOf (import ../dependencies.nix).drvPath "out"' \
+    'builtins.outputOf (import ../dependencies.nix {}).drvPath "out"' \
     | grepQuiet "has a context which refers to a complete source and binary closure. This is not supported at this time"
 
 # Test using `builtins.outputOf` with static derivations

tests/export-graph.nix

@@ -17,13 +17,13 @@ rec {
   foo."bar.runtimeGraph" = mkDerivation {
     name = "dependencies";
     builder = builtins.toFile "build-graph-builder" "${printRefs}";
-    exportReferencesGraph = ["refs" (import ./dependencies.nix)];
+    exportReferencesGraph = ["refs" (import ./dependencies.nix {})];
   };
 
   foo."bar.buildGraph" = mkDerivation {
     name = "dependencies";
     builder = builtins.toFile "build-graph-builder" "${printRefs}";
-    exportReferencesGraph = ["refs" (import ./dependencies.nix).drvPath];
+    exportReferencesGraph = ["refs" (import ./dependencies.nix {}).drvPath];
   };
 
 }

tests/remote-store.sh

@@ -24,7 +24,7 @@ fi
   import (
     mkDerivation {
       name = "foo";
-      bla = import ./dependencies.nix;
+      bla = import ./dependencies.nix {};
       buildCommand = "
         echo \\\"hi\\\" > $out
       ";