"Downstream placeholders" should not be store paths

Insead they should be opaque `/<hash>` like the placeholders we already
have.

3 files changed, 7 insertions, 9 deletions

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 0ddba6384..d28024639 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -82,13 +82,13 @@ static void mkOutputString(EvalState & state, Value & v,
     auto optOutputPath = o.second.pathOpt(*state.store, drv.name, o.first);
     mkString(
         *state.allocAttr(v, state.symbols.create(o.first)),
-        state.store->printStorePath(optOutputPath
-            ? *optOutputPath
+        optOutputPath
+            ? state.store->printStorePath(*optOutputPath)
             /* Downstream we would substitute this for an actual path once
                we build the floating CA derivation */
             /* FIXME: we need to depend on the basic derivation, not
                derivation */
-            : downstreamPlaceholder(*state.store, drvPath, o.first)),
+            : downstreamPlaceholder(*state.store, drvPath, o.first),
         {"!" + o.first + "!" + state.store->printStorePath(drvPath)});
 }
 
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index fb1d06466..5319c1a38 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -664,14 +664,12 @@ std::string hashPlaceholder(const std::string & outputName)
     return "/" + hashString(htSHA256, "nix-output:" + outputName).to_string(Base32, false);
 }
 
-StorePath downstreamPlaceholder(const Store & store, const StorePath & drvPath, std::string_view outputName)
+std::string downstreamPlaceholder(const Store & store, const StorePath & drvPath, std::string_view outputName)
 {
     auto drvNameWithExtension = drvPath.name();
     auto drvName = drvNameWithExtension.substr(0, drvNameWithExtension.size() - 4);
-    return store.makeStorePath(
-        "downstream-placeholder:" + std::string { drvPath.name() } + ":" + std::string { outputName },
-        "compressed:" + std::string { drvPath.hashPart() },
-        outputPathName(drvName, outputName));
+    auto clearText = "nix-upstream-output:" + std::string { drvPath.hashPart() } + ":" + outputPathName(drvName, outputName);
+    return "/" + hashString(htSHA256, clearText).to_string(Base32, false);
 }
 
 }
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 49374d046..76f983561 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -196,6 +196,6 @@ void writeDerivation(Sink & out, const Store & store, const BasicDerivation & dr
 
 std::string hashPlaceholder(const std::string & outputName);
 
-StorePath downstreamPlaceholder(const Store & store, const StorePath & drvPath, std::string_view outputName);
+std::string downstreamPlaceholder(const Store & store, const StorePath & drvPath, std::string_view outputName);
 
 }