New store settings system

Motivation:

See the linked issues for details.

The most notable user-relevant bits are:

- This cleans up the `MountedSSHStore`: decomposed into its orthogonal parts

- This brings us pretty close to being able to then implement a JSON-based config.
   - Store query parameters can be JSON
   - Stores can entirely be specified via JSON objects, but this is not yet hooked up to anything.

Also behind the scenes have these benefits:

1. The docs are moved out of the headers, good for less rebuilding when they changes
2. Stores are always constructed from store configs
3. Use JSON, avoid custom serializers

Context:

Part of #11106
Part of #10766

Author: Ericson2314

doc/manual/generate-settings.nix

@@ -19,19 +19,32 @@ in
   prefix,
   inlineHTML ? true,
 }:
-settingsInfo:
 
 let
 
   showSetting =
     prefix: setting:
     {
       description,
-      documentDefault,
-      defaultValue,
-      aliases,
-      value,
+
       experimentalFeature,
+
+      # Whether we document the default, because it is machine agostic,
+      # or don't because because it is machine-specific.
+      documentDefault ? true,
+
+      # The default value is JSON for new-style config, rather than then
+      # a string or boolean, for old-style config.
+      json ? false,
+
+      defaultValue ? null,
+
+      subSettings ? null,
+
+      aliases ? [ ],
+
+      # The current value for this setting. Purposefully unused.
+      value ? null,
     }:
     let
       result = squash ''
@@ -50,7 +63,7 @@ let
 
         ${description}
 
-        **Default:** ${showDefault documentDefault defaultValue}
+        ${showDefaultOrSubSettings}
 
         ${showAliases aliases}
       '';
@@ -72,9 +85,24 @@ let
         > ```
       '';
 
+      showDefaultOrSubSettings =
+        if !isAttrs subSettings then
+          # No subsettings, instead single setting. Show the default value.
+          ''
+            **Default:** ${showDefault}
+          ''
+        else
+          # Indent the nested sub-settings, and append the outer setting name onto the prefix
+          indent "  " ''
+            **Nullable sub-settings**: ${if subSettings.nullable then "true" else "false"}
+            ${builtins.trace prefix (showSettings "${prefix}-${setting}" subSettings.map)}
+          '';
+
       showDefault =
-        documentDefault: defaultValue:
         if documentDefault then
+          if json then
+            "`${builtins.toJSON defaultValue}`"
+          else
           # a StringMap value type is specified as a string, but
           # this shows the value type. The empty stringmap is `null` in
           # JSON, but that converts to `{ }` here.
@@ -95,5 +123,7 @@ let
     in
     result;
 
+  showSettings =
+    prefix: settingsInfo: concatStrings (attrValues (mapAttrs (showSetting prefix) settingsInfo));
 in
-concatStrings (attrValues (mapAttrs (showSetting prefix) settingsInfo))
+showSettings prefix

doc/manual/generate-store-info.nix

@@ -33,6 +33,7 @@ let
     {
       settings,
       doc,
+      uri-schemes,
       experimentalFeature,
     }:
     let

src/build-remote/build-remote.cc

@@ -16,7 +16,7 @@
 #include "nix/store/globals.hh"
 #include "nix/util/serialise.hh"
 #include "nix/store/build-result.hh"
-#include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 #include "nix/util/strings.hh"
 #include "nix/store/derivations.hh"
 #include "nix/store/local-store.hh"
@@ -44,7 +44,7 @@ static AutoCloseFD openSlotLock(const Machine & m, uint64_t slot)
 
 static bool allSupportedLocally(Store & store, const std::set<std::string>& requiredFeatures) {
     for (auto & feature : requiredFeatures)
-        if (!store.systemFeatures.get().count(feature)) return false;
+        if (!store.config.systemFeatures.get().count(feature)) return false;
     return true;
 }
 
@@ -85,7 +85,7 @@ static int main_build_remote(int argc, char * * argv)
            that gets cleared on reboot, but it wouldn't work on macOS. */
         auto currentLoadName = "/current-load";
         if (auto localStore = store.dynamic_pointer_cast<LocalFSStore>())
-            currentLoad = std::string { localStore->stateDir } + currentLoadName;
+            currentLoad = std::string { localStore->config.stateDir } + currentLoadName;
         else
             currentLoad = settings.nixStateDir + currentLoadName;
 

src/libcmd/command.cc

@@ -3,7 +3,7 @@
 
 #include "nix/cmd/command.hh"
 #include "nix/cmd/markdown.hh"
-#include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 #include "nix/store/local-fs-store.hh"
 #include "nix/store/derivations.hh"
 #include "nix/expr/nixexpr.hh"

src/libcmd/common-eval-args.cc

@@ -9,7 +9,7 @@
 #include "nix/fetchers/registry.hh"
 #include "nix/flake/flakeref.hh"
 #include "nix/flake/settings.hh"
-#include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 #include "nix/cmd/command.hh"
 #include "nix/fetchers/tarball.hh"
 #include "nix/fetchers/fetch-to-store.hh"

src/libcmd/include/nix/cmd/command.hh

@@ -18,7 +18,7 @@ extern char ** savedArgv;
 class EvalState;
 struct Pos;
 class Store;
-class LocalFSStore;
+struct LocalFSStore;
 
 static constexpr Command::Category catHelp = -1;
 static constexpr Command::Category catSecondary = 100;

src/libcmd/repl.cc

@@ -12,7 +12,7 @@
 #include "nix/expr/eval-settings.hh"
 #include "nix/expr/attr-path.hh"
 #include "nix/util/signals.hh"
-#include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 #include "nix/store/log-store.hh"
 #include "nix/cmd/common-eval-args.hh"
 #include "nix/expr/get-drvs.hh"

src/libexpr/primops/fetchClosure.cc

@@ -1,5 +1,5 @@
 #include "nix/expr/primops.hh"
-#include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 #include "nix/store/realisation.hh"
 #include "nix/store/make-content-addressed.hh"
 #include "nix/util/url.hh"

src/libstore-c/nix_api_store.cc

@@ -5,6 +5,7 @@
 
 #include "nix/store/path.hh"
 #include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 #include "nix/store/build-result.hh"
 
 #include "nix/store/globals.hh"
@@ -42,7 +43,7 @@ Store * nix_store_open(nix_c_context * context, const char * uri, const char ***
         if (!params)
             return new Store{nix::openStore(uri_str)};
 
-        nix::Store::Params params_map;
+        nix::StoreReference::Params params_map;
         for (size_t i = 0; params[i] != nullptr; i++) {
             params_map[params[i][0]] = params[i][1];
         }

src/libstore-test-support/include/nix/store/tests/libstore.hh

@@ -5,6 +5,7 @@
 #include <gmock/gmock.h>
 
 #include "nix/store/store-api.hh"
+#include "nix/store/store-open.hh"
 
 namespace nix {
 

src/libstore-tests/data/store-reference/auto.json

@@ -0,0 +1,3 @@
+{
+  "scheme": "auto"
+}

src/libstore-tests/data/store-reference/auto_param.json

@@ -0,0 +1,4 @@
+{
+  "root": "/foo/bar/baz",
+  "scheme": "auto"
+}

src/libstore-tests/data/store-reference/local_1.json

@@ -0,0 +1,5 @@
+{
+  "authority": "",
+  "root": "/foo/bar/baz",
+  "scheme": "local"
+}

src/libstore-tests/data/store-reference/local_2.json

@@ -0,0 +1,5 @@
+{
+  "authority": "/foo/bar/baz",
+  "scheme": "local",
+  "trusted": true
+}

src/libstore-tests/data/store-reference/ssh.json

@@ -0,0 +1,4 @@
+{
+  "authority": "localhost",
+  "scheme": "ssh"
+}

src/libstore-tests/data/store-reference/unix.json

@@ -0,0 +1,6 @@
+{
+  "authority": "",
+  "max-connections": 7,
+  "scheme": "unix",
+  "trusted": true
+}

src/libstore-tests/dummy-store.cc

@@ -0,0 +1,20 @@
+#include <gtest/gtest.h>
+
+#include "nix/store/dummy-store.hh"
+#include "nix/store/globals.hh"
+
+namespace nix {
+
+TEST(DummyStore, constructConfig)
+{
+    DummyStoreConfig config{"dummy", "", {}};
+
+    EXPECT_EQ(config.storeDir, settings.nixStore);
+}
+
+TEST(DummyStore, constructConfigNoAuthority)
+{
+    EXPECT_THROW(DummyStoreConfig("dummy", "not-allowed", {}), UsageError);
+}
+
+} // namespace nix

src/libstore-tests/legacy-ssh-store.cc

@@ -9,11 +9,13 @@ TEST(LegacySSHStore, constructConfig)
     LegacySSHStoreConfig config{
         "ssh",
         "localhost",
-        StoreConfig::Params{
+        StoreReference::Params{
             {
                 "remote-program",
-                // TODO #11106, no more split on space
-                "foo bar",
+                {
+                    "foo",
+                    "bar",
+                },
             },
         }};
     EXPECT_EQ(

src/libstore-tests/local-overlay-store.cc

@@ -1,9 +1,6 @@
-// FIXME: Odd failures for templates that are causing the PR to break
-// for now with discussion with @Ericson2314 to comment out.
-#if 0
-#  include <gtest/gtest.h>
+#include <gtest/gtest.h>
 
-#  include "nix/store/local-overlay-store.hh"
+#include "nix/store/local-overlay-store.hh"
 
 namespace nix {
 
@@ -31,4 +28,3 @@ TEST(LocalOverlayStore, constructConfig_rootPath)
 }
 
 } // namespace nix
-#endif

src/libstore-tests/local-store.cc

@@ -1,15 +1,6 @@
-// FIXME: Odd failures for templates that are causing the PR to break
-// for now with discussion with @Ericson2314 to comment out.
-#if 0
-#  include <gtest/gtest.h>
+#include <gtest/gtest.h>
 
-#  include "nix/store/local-store.hh"
-
-// Needed for template specialisations. This is not good! When we
-// overhaul how store configs work, this should be fixed.
-#  include "nix/util/args.hh"
-#  include "nix/util/config-impl.hh"
-#  include "nix/util/abstract-setting-to-json.hh"
+#include "nix/store/local-store.hh"
 
 namespace nix {
 
@@ -37,4 +28,3 @@ TEST(LocalStore, constructConfig_rootPath)
 }
 
 } // namespace nix
-#endif

src/libstore-tests/meson.build

@@ -58,6 +58,7 @@ sources = files(
   'derivation-advanced-attrs.cc',
   'derivation.cc',
   'derived-path.cc',
+  'dummy-store.cc',
   'downstream-placeholder.cc',
   'http-binary-cache-store.cc',
   'legacy-ssh-store.cc',

src/libstore-tests/nix_api_store.cc

@@ -97,7 +97,7 @@ TEST_F(nix_api_util_context, nix_store_open_dummy)
     nix_libstore_init(ctx);
     Store * store = nix_store_open(ctx, "dummy://", nullptr);
     ASSERT_EQ(NIX_OK, ctx->last_err_code);
-    ASSERT_STREQ("dummy", store->ptr->getUri().c_str());
+    ASSERT_STREQ("dummy://", store->ptr->getUri().c_str());
 
     std::string str;
     nix_store_get_version(ctx, store, OBSERVE_STRING(str));