Test the builtins.parseFlakeRef primop

Simple unit tests, but already catch half of the issue behind #6633 (comment)

src/libexpr/flake/flakeref.cc

@@ -55,7 +55,7 @@ FlakeRef parseFlakeRef(
 {
     auto [flakeRef, fragment] = parseFlakeRefWithFragment(url, baseDir, allowMissing, isFlake);
     if (fragment != "")
-        throw Error("unexpected fragment '%s' in flake reference '%s'", fragment, url);
+        throw FlakeRefError("unexpected fragment '%s' in flake reference '%s'", fragment, url);
     return flakeRef;
 }
 
@@ -113,10 +113,10 @@ std::pair<FlakeRef, std::string> parsePathFlakeRefWithFragment(
                         found = true;
                         break;
                     } else if (pathExists(path + "/.git"))
-                        throw Error("path '%s' is not part of a flake (neither it nor its parent directories contain a 'flake.nix' file)", path);
+                        throw FlakeRefError("path '%s' is not part of a flake (neither it nor its parent directories contain a 'flake.nix' file)", path);
                     else {
                         if (lstat(path).st_dev != device)
-                            throw Error("unable to find a flake before encountering filesystem boundary at '%s'", path);
+                            throw FlakeRefError("unable to find a flake before encountering filesystem boundary at '%s'", path);
                     }
                     path = dirOf(path);
                 }
@@ -148,7 +148,7 @@ std::pair<FlakeRef, std::string> parsePathFlakeRefWithFragment(
 
                     if (subdir != "") {
                         if (parsedURL.query.count("dir"))
-                            throw Error("flake URL '%s' has an inconsistent 'dir' parameter", url);
+                            throw FlakeRefError("flake URL '%s' has an inconsistent 'dir' parameter", url);
                         parsedURL.query.insert_or_assign("dir", subdir);
                     }
 

src/libexpr/flake/flakeref.hh

@@ -15,6 +15,8 @@ class Store;
 
 typedef std::string FlakeId;
 
+MakeError(FlakeRefError, Error);
+
 /**
  * A flake reference specifies how to fetch a flake or raw source
  * (e.g. from a Git repository).  It is created from a URL-like syntax

tests/unit/libexpr/primops.cc

@@ -3,6 +3,7 @@
 
 #include "eval-settings.hh"
 #include "memory-input-accessor.hh"
+#include "flake/flakeref.hh"
 
 #include "tests/libexpr.hh"
 
@@ -855,4 +856,35 @@ namespace nix {
         auto v = eval("builtins.genericClosure { startSet = []; }");
         ASSERT_THAT(v, IsListOfSize(0));
     }
+
+    TEST_F(PrimOpTest, parseFlakeRef) {
+        auto getAttrStr = [&](Value attrSet, std::string attrName) -> Value * {
+            auto attr = attrSet.attrs->get(createSymbol(attrName.c_str()));
+            if (attr == nullptr) {
+                ADD_FAILURE();
+                return new Value(); // Just so that it doesn't crash
+            }
+            return attr->value;
+        };
+
+        // These two refs should be equivalent
+        auto ref1 = "/foo/bar?lastModified=5";
+        auto ref2 = "/foo/bar?lastModified=5#";
+
+        for (auto ref : std::vector<std::string>{ref1, ref2}) {
+            auto v = eval(fmt("builtins.parseFlakeRef \"%s\"", ref));
+            ASSERT_THAT(v, IsAttrsOfSize(3));
+
+            EXPECT_THAT(*getAttrStr(v, "type"), IsStringEq("path"));
+            EXPECT_THAT(*getAttrStr(v, "path"), IsStringEq("/foo/bar"));
+            EXPECT_THAT(*getAttrStr(v, "lastModified"), IsIntEq(5));
+        }
+    }
+    TEST_F(PrimOpTest, parseFlakeRefWithFragment) {
+        // Throws because `builtins.parseFlakeRef` doesn't accept a fragment
+        EXPECT_THROW(
+                eval("builtins.parseFlakeRef \"/foo/bar?lastModified=5#foo\""),
+                FlakeRefError
+        );
+    }
 } /* namespace nix */