nix develop: Set output paths to writable locations

Currently, they're set to $(pwd)/outputs/$outputName. This allows
commands like 'make install' to work.

flake.nix

@@ -421,6 +421,8 @@
         stdenv.mkDerivation {
           name = "nix";
 
+          outputs = [ "out" "dev" "doc" ];
+
           buildInputs = buildDeps ++ propagatedDeps ++ perlDeps;
 
           inherit configureFlags;
@@ -428,15 +430,6 @@
           enableParallelBuilding = true;
 
           installFlags = "sysconfdir=$(out)/etc";
-
-          shellHook =
-            ''
-              export prefix=$(pwd)/inst
-              configureFlags+=" --prefix=$prefix"
-              PKG_CONFIG_PATH=$prefix/lib/pkgconfig:$PKG_CONFIG_PATH
-              PATH=$prefix/bin:$PATH
-              unset PYTHONPATH
-            '';
         });
 
   };

src/nix/develop.cc

@@ -15,7 +15,7 @@ struct Var
 {
     bool exported = true;
     bool associative = false;
-    std::string value; // quoted string or array
+    std::string quoted; // quoted string or array
 };
 
 struct BuildEnvironment
@@ -75,12 +75,12 @@ BuildEnvironment readEnvironment(const Path & path)
 
         else if (std::regex_search(pos, file.cend(), match, varRegex, std::regex_constants::match_continuous)) {
             pos = match[0].second;
-            res.env.insert({match[1], Var { .exported = exported.count(match[1]) > 0, .value = match[2] }});
+            res.env.insert({match[1], Var { .exported = exported.count(match[1]) > 0, .quoted = match[2] }});
         }
 
         else if (std::regex_search(pos, file.cend(), match, assocArrayRegex, std::regex_constants::match_continuous)) {
             pos = match[0].second;
-            res.env.insert({match[1], Var { .associative = true, .value = match[2] }});
+            res.env.insert({match[1], Var { .associative = true, .quoted = match[2] }});
         }
 
         else if (std::regex_search(pos, file.cend(), match, functionRegex, std::regex_constants::match_continuous)) {
@@ -92,6 +92,8 @@ BuildEnvironment readEnvironment(const Path & path)
             path, file.substr(pos - file.cbegin(), 60));
     }
 
+    res.env.erase("__output");
+
     return res;
 }
 
@@ -125,27 +127,32 @@ StorePath getDerivationEnvironment(ref<Store> store, const StorePath & drvPath)
     /* Rehash and write the derivation. FIXME: would be nice to use
        'buildDerivation', but that's privileged. */
     drv.name += "-env";
-    for (auto & output : drv.outputs)
-        drv.env.erase(output.first);
-    drv.outputs = {{"out", DerivationOutput { .output = DerivationOutputInputAddressed { .path = StorePath::dummy }}}};
-    drv.env["out"] = "";
-    drv.env["_outputs_saved"] = drv.env["outputs"];
-    drv.env["outputs"] = "out";
+    for (auto & output : drv.outputs) {
+        output.second = { .output = DerivationOutputInputAddressed { .path = StorePath::dummy } };
+        drv.env[output.first] = "";
+    }
     drv.inputSrcs.insert(std::move(getEnvShPath));
     Hash h = std::get<0>(hashDerivationModulo(*store, drv, true));
-    auto shellOutPath = store->makeOutputPath("out", h, drv.name);
-    drv.outputs.insert_or_assign("out", DerivationOutput { .output = DerivationOutputInputAddressed {
-                .path = shellOutPath
-            } });
-    drv.env["out"] = store->printStorePath(shellOutPath);
-    auto shellDrvPath2 = writeDerivation(*store, drv);
+
+    for (auto & output : drv.outputs) {
+        auto outPath = store->makeOutputPath(output.first, h, drv.name);
+        output.second = { .output = DerivationOutputInputAddressed { .path = outPath } };
+        drv.env[output.first] = store->printStorePath(outPath);
+    }
+
+    auto shellDrvPath = writeDerivation(*store, drv);
 
     /* Build the derivation. */
-    store->buildPaths({{shellDrvPath2}});
+    store->buildPaths({{shellDrvPath}});
 
-    assert(store->isValidPath(shellOutPath));
+    for (auto & outPath : drv.outputPaths(*store)) {
+        assert(store->isValidPath(outPath));
+        auto outPathS = store->toRealPath(outPath);
+        if (lstat(outPathS).st_size)
+            return outPath;
+    }
 
-    return shellOutPath;
+    throw Error("get-env.sh failed to produce an environment");
 }
 
 struct Common : InstallableCommand, MixProfile
@@ -171,8 +178,12 @@ struct Common : InstallableCommand, MixProfile
         "UID",
     };
 
-    void makeRcScript(const BuildEnvironment & buildEnvironment, std::ostream & out)
+    std::string makeRcScript(
+        const BuildEnvironment & buildEnvironment,
+        const Path & outputsDir = absPath(".") + "/outputs")
     {
+        std::ostringstream out;
+
         out << "unset shellHook\n";
 
         out << "nix_saved_PATH=\"$PATH\"\n";
@@ -180,9 +191,9 @@ struct Common : InstallableCommand, MixProfile
         for (auto & i : buildEnvironment.env) {
             if (!ignoreVars.count(i.first) && !hasPrefix(i.first, "BASH_")) {
                 if (i.second.associative)
-                    out << fmt("declare -A %s=(%s)\n", i.first, i.second.value);
+                    out << fmt("declare -A %s=(%s)\n", i.first, i.second.quoted);
                 else {
-                    out << fmt("%s=%s\n", i.first, i.second.value);
+                    out << fmt("%s=%s\n", i.first, i.second.quoted);
                     if (i.second.exported)
                         out << fmt("export %s\n", i.first);
                 }
@@ -193,13 +204,26 @@ struct Common : InstallableCommand, MixProfile
 
         out << buildEnvironment.bashFunctions << "\n";
 
-        // FIXME: set outputs
-
         out << "export NIX_BUILD_TOP=\"$(mktemp -d --tmpdir nix-shell.XXXXXX)\"\n";
         for (auto & i : {"TMP", "TMPDIR", "TEMP", "TEMPDIR"})
             out << fmt("export %s=\"$NIX_BUILD_TOP\"\n", i);
 
         out << "eval \"$shellHook\"\n";
+
+        /* Substitute occurrences of output paths. */
+        auto outputs = buildEnvironment.env.find("outputs");
+        assert(outputs != buildEnvironment.env.end());
+
+        // FIXME: properly unquote 'outputs'.
+        StringMap rewrites;
+        for (auto & outputName : tokenizeString<std::vector<std::string>>(replaceStrings(outputs->second.quoted, "'", ""))) {
+            auto from = buildEnvironment.env.find(outputName);
+            assert(from != buildEnvironment.env.end());
+            // FIXME: unquote
+            rewrites.insert({from->second.quoted, outputsDir + "/" + outputName});
+        }
+
+        return rewriteStrings(out.str(), rewrites);
     }
 
     Strings getDefaultFlakeAttrPaths() override
@@ -288,19 +312,18 @@ struct CmdDevelop : Common, MixEnvironment
 
         auto [rcFileFd, rcFilePath] = createTempFile("nix-shell");
 
-        std::ostringstream ss;
-        makeRcScript(buildEnvironment, ss);
+        auto script = makeRcScript(buildEnvironment);
 
-        ss << fmt("rm -f '%s'\n", rcFilePath);
+        script +=  fmt("rm -f '%s'\n", rcFilePath);
 
         if (!command.empty()) {
             std::vector<std::string> args;
             for (auto s : command)
                 args.push_back(shellEscape(s));
-            ss << fmt("exec %s\n", concatStringsSep(" ", args));
+            script += fmt("exec %s\n", concatStringsSep(" ", args));
         }
 
-        writeFull(rcFileFd.get(), ss.str());
+        writeFull(rcFileFd.get(), script);
 
         stopProgressBar();
 
@@ -362,7 +385,7 @@ struct CmdPrintDevEnv : Common
 
         stopProgressBar();
 
-        makeRcScript(buildEnvironment, std::cout);
+        std::cout << makeRcScript(buildEnvironment);
     }
 };
 

src/nix/get-env.sh

@@ -1,12 +1,6 @@
 set -e
 if [ -e .attrs.sh ]; then source .attrs.sh; fi
 
-outputs=$_outputs_saved
-for __output in $_outputs_saved; do
-    declare "$__output"="$out"
-done
-unset _outputs_saved __output
-
 export IN_NIX_SHELL=impure
 export dontAddDisableDepTrack=1
 
@@ -14,5 +8,12 @@ if [[ -n $stdenv ]]; then
     source $stdenv/setup
 fi
 
-export > $out
-set >> $out
+for __output in $outputs; do
+    if [[ -z $__done ]]; then
+        export > ${!__output}
+        set >> ${!__output}
+        __done=1
+    else
+        echo -n >> ${!__output}
+    fi
+done