14 files changed, 154 insertions, 5 deletions
diff --git a/src/libutil/config.cc b/src/libutil/config.cc
index 8e76d6d66..81efcd507 100644
--- a/src/libutil/config.cc
+++ b/src/libutil/config.cc
@@ -437,6 +437,34 @@ void OptionalPathSetting::operator =(const std::optional<Path> & v)
     this->assign(v);
 }
 
+PathsSetting::PathsSetting(Config * options,
+    const Paths & def,
+    const std::string & name,
+    const std::string & description,
+    const std::set<std::string> & aliases)
+    : BaseSetting<Paths>(def, true, name, description, aliases)
+{
+    options->addSetting(this);
+}
+
+
+Paths PathsSetting::parse(const std::string & str) const
+{
+    auto strings = tokenizeString<Strings>(str);
+    Paths parsed;
+
+    for (auto str : strings) {
+        parsed.push_back(canonPath(str));
+    }
+
+    return parsed;
+}
+
+PathsSetting::operator bool() const noexcept
+{
+    return !get().empty();
+}
+
 bool GlobalConfig::set(const std::string & name, const std::string & value)
 {
     for (auto & config : *configRegistrations)
diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index 3e232d224..01e1239b3 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -375,6 +375,26 @@ public:
     void operator =(const std::optional<Path> & v);
 };
 
+/**
+ * Like `OptionalPathSetting`, but allows multiple paths.
+ */
+class PathsSetting : public BaseSetting<Paths>
+{
+public:
+
+    PathsSetting(Config * options,
+        const Paths & def,
+        const std::string & name,
+        const std::string & description,
+        const std::set<std::string> & aliases = {});
+
+    Paths parse(const std::string & str) const override;
+
+    void operator =(const Paths & v);
+
+    operator bool() const noexcept;
+};
+
 struct GlobalConfig : public AbstractConfig
 {
     typedef std::vector<Config*> ConfigRegistrations;
diff --git a/tests/functional/lang/eval-fail-eol-1.err.exp b/tests/functional/lang/parse-fail-eol-1.err.exp
index 3f5a5c22c..f7f79b460 100644
--- a/tests/functional/lang/eval-fail-eol-1.err.exp
+++ b/tests/functional/lang/parse-fail-eol-1.err.exp
@@ -1,5 +1,5 @@
 error: undefined variable 'invalid'
-       at /pwd/lang/eval-fail-eol-1.nix:2:1:
+       at «stdin»:2:1:
             1| # foo
             2| invalid
              | ^
diff --git a/tests/functional/lang/eval-fail-eol-1.nix b/tests/functional/lang/parse-fail-eol-1.nix
index 476223919..476223919 100644
--- a/tests/functional/lang/eval-fail-eol-1.nix
+++ b/tests/functional/lang/parse-fail-eol-1.nix
diff --git a/tests/functional/lang/eval-fail-eol-3.err.exp b/tests/functional/lang/parse-fail-eol-2.err.exp
index ada3c5ecd..f7f79b460 100644
--- a/tests/functional/lang/eval-fail-eol-3.err.exp
+++ b/tests/functional/lang/parse-fail-eol-2.err.exp
@@ -1,5 +1,5 @@
 error: undefined variable 'invalid'
-       at /pwd/lang/eval-fail-eol-3.nix:2:1:
+       at «stdin»:2:1:
             1| # foo
             2| invalid
              | ^
diff --git a/tests/functional/lang/eval-fail-eol-2.nix b/tests/functional/lang/parse-fail-eol-2.nix
index 0cf92a425..0cf92a425 100644
--- a/tests/functional/lang/eval-fail-eol-2.nix
+++ b/tests/functional/lang/parse-fail-eol-2.nix
diff --git a/tests/functional/lang/eval-fail-eol-2.err.exp b/tests/functional/lang/parse-fail-eol-3.err.exp
index ff13e2d55..f7f79b460 100644
--- a/tests/functional/lang/eval-fail-eol-2.err.exp
+++ b/tests/functional/lang/parse-fail-eol-3.err.exp
@@ -1,5 +1,5 @@
 error: undefined variable 'invalid'
-       at /pwd/lang/eval-fail-eol-2.nix:2:1:
+       at «stdin»:2:1:
             1| # foo
             2| invalid
              | ^
diff --git a/tests/functional/lang/eval-fail-eol-3.nix b/tests/functional/lang/parse-fail-eol-3.nix
index 33422452d..33422452d 100644
--- a/tests/functional/lang/eval-fail-eol-3.nix
+++ b/tests/functional/lang/parse-fail-eol-3.nix
diff --git a/tests/functional/lang/eval-fail-path-slash.err.exp b/tests/functional/lang/parse-fail-path-slash.err.exp
index e3531d352..0407543a1 100644
--- a/tests/functional/lang/eval-fail-path-slash.err.exp
+++ b/tests/functional/lang/parse-fail-path-slash.err.exp
@@ -1,5 +1,5 @@
 error: path has a trailing slash
-       at /pwd/lang/eval-fail-path-slash.nix:6:12:
+       at «stdin»:6:12:
             5| # and https://nixos.org/nix-dev/2016-June/020829.html
             6| /nix/store/
              |            ^
diff --git a/tests/functional/lang/eval-fail-path-slash.nix b/tests/functional/lang/parse-fail-path-slash.nix
index 8c2e104c7..8c2e104c7 100644
--- a/tests/functional/lang/eval-fail-path-slash.nix
+++ b/tests/functional/lang/parse-fail-path-slash.nix
diff --git a/tests/functional/lang/eval-fail-set.err.exp b/tests/functional/lang/parse-fail-set.err.exp
index 6dd646e11..2f77406a7 100644
--- a/tests/functional/lang/eval-fail-set.err.exp
+++ b/tests/functional/lang/parse-fail-set.err.exp
@@ -1,5 +1,5 @@
 error: undefined variable 'x'
-       at /pwd/lang/eval-fail-set.nix:1:3:
+       at «stdin»:1:3:
             1| 8.x
              |   ^
             2|
diff --git a/tests/functional/lang/eval-fail-set.nix b/tests/functional/lang/parse-fail-set.nix
index c6b7980b6..c6b7980b6 100644
--- a/tests/functional/lang/eval-fail-set.nix
+++ b/tests/functional/lang/parse-fail-set.nix
diff --git a/tests/unit/libutil/paths-setting.cc b/tests/unit/libutil/paths-setting.cc
new file mode 100644
index 000000000..b450b0cf9
--- /dev/null
+++ b/tests/unit/libutil/paths-setting.cc
@@ -0,0 +1,100 @@
+#include "config.hh"
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+#include <sstream>
+
+using testing::Eq;
+
+namespace nix {
+
+class PathsSettingTestConfig : public Config
+{
+public:
+    PathsSettingTestConfig()
+        : Config()
+    { }
+
+    PathsSetting paths{this, Paths(), "paths", "documentation"};
+};
+
+struct PathsSettingTest : public ::testing::Test {
+public:
+    PathsSettingTestConfig mkConfig()
+    {
+        return PathsSettingTestConfig();
+    }
+};
+
+TEST_F(PathsSettingTest, parse) {
+    auto config = mkConfig();
+    // Not an absolute path:
+    ASSERT_THROW(config.paths.parse("puppy.nix"), Error);
+
+    ASSERT_THAT(
+        config.paths.parse("/puppy.nix"),
+        Eq<Paths>({"/puppy.nix"})
+    );
+
+    // Splits on whitespace:
+    ASSERT_THAT(
+        config.paths.parse("/puppy.nix /doggy.nix"),
+        Eq<Paths>({"/puppy.nix", "/doggy.nix"})
+    );
+
+    // Splits on _any_ whitespace:
+    ASSERT_THAT(
+        config.paths.parse("/puppy.nix \t  /doggy.nix\n\n\n/borzoi.nix\r/goldie.nix"),
+        Eq<Paths>({"/puppy.nix", "/doggy.nix", "/borzoi.nix", "/goldie.nix"})
+    );
+
+    // Canonicizes paths:
+    ASSERT_THAT(
+        config.paths.parse("/puppy/../doggy.nix"),
+        Eq<Paths>({"/doggy.nix"})
+    );
+}
+
+TEST_F(PathsSettingTest, bool) {
+    auto config = mkConfig();
+    // No paths:
+    ASSERT_FALSE(config.paths);
+    // Set a path:
+    config.set("paths", "/puppy.nix");
+    // Now there are paths:
+    ASSERT_TRUE(config.paths);
+
+    // Multiple paths count too:
+    config.set("paths", "/puppy.nix /doggy.nix");
+    ASSERT_TRUE(config.paths);
+}
+
+TEST_F(PathsSettingTest, append) {
+    auto config = mkConfig();
+
+    ASSERT_TRUE(config.paths.isAppendable());
+
+    // Starts with no paths:
+    ASSERT_THAT(
+        config.paths.get(),
+        Eq<Paths>({})
+    );
+
+    // Can append a path:
+    config.paths.set("/puppy.nix", true);
+
+    ASSERT_THAT(
+        config.paths.get(),
+        Eq<Paths>({"/puppy.nix"})
+    );
+
+    // Can append multiple paths:
+    config.paths.set("/silly.nix /doggy.nix", true);
+
+    ASSERT_THAT(
+        config.paths.get(),
+        Eq<Paths>({"/puppy.nix", "/silly.nix", "/doggy.nix"})
+    );
+}
+
+} // namespace nix
diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 60bb2de89..a05776eca 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -46,6 +46,7 @@ libutil_tests_sources = files(
   'libutil/json-utils.cc',
   'libutil/logging.cc',
   'libutil/lru-cache.cc',
+  'libutil/paths-setting.cc',
   'libutil/pool.cc',
   'libutil/references.cc',
   'libutil/suggestions.cc',