nix/doctor: check nixpkgs provenance

Many issues stems from `<nixpkgs>` not resolving anywhere or having the
wrong version, let's make it awfully obvious again here.

Towards #230.

Change-Id: If630e9616566e77143f028cdcfe0b7f00a1d486d
Signed-off-by: Raito Bezarius <raito@lix.systems>

doc/manual/rl-next/nix-doctor.md

@@ -0,0 +1,12 @@
+---
+synopsis: "Improve nix doctor"
+cls: [5316, 5317, 5318, 5319, 5320]
+category: Features
+credits: [rootile, raito]
+---
+The `nix doctor` diagnosics interface now provides a lot more useful information including, but not limited to:
+- General system information (OS, Hardware etc)
+- Nix Information like Sandbox, Version, Store, State and other directories
+- Flake registry
+- Search path Information
+- Nixpkgs provenance

lix/nix/doctor.cc

@@ -113,6 +113,10 @@ struct CmdDoctor : StoreCommand
             printInfo("Collecting information about the ambient Nix search paths");
             success &= checkAmbientNixSearchPaths();
         }
+        {
+            printInfo("Collecting information about Nixpkgs provenance");
+            success &= checkNixpkgsProvenance();
+        }
 
         if (!success)
             throw Exit(2);
@@ -221,6 +225,41 @@ struct CmdDoctor : StoreCommand
             checkInfo(fmt("Overridden Nix configuration search path: %s", nixPathS));
         }
 
+        // Parse all entries one by one to construct the search path.
+        for (auto entry : evalSettings.nixPath.get()) {
+            auto elem = SearchPath::Elem::parse(entry);
+            auto prefix = elem.prefix.s.empty() ? elem.path.s : elem.prefix.s;
+            searchPathFacts[prefix] = {
+                .originReference = entry,
+            };
+        }
+
+        return true;
+    }
+
+    bool checkNixpkgsProvenance()
+    {
+        if (!searchPathFacts.contains("nixpkgs")) {
+            return checkFail(
+                "Search path does not contain nixpkgs. All evaluations using nixpkgs (including nix-shell) "
+                "will fail."
+            );
+        }
+
+        auto entry = searchPathFacts["nixpkgs"];
+        checkInfo(fmt("Nixpkgs provenance: %s", entry.originReference));
+        try {
+            auto nixpkgsVersion = aio().blockOn(runProgram(
+                "nix-instantiate",
+                true,
+                {"--eval", "--raw", "--expr", "(import <nixpkgs> { }).lib.version"},
+                false
+            ));
+            checkInfo(fmt("Nixpkgs version: %s", nixpkgsVersion));
+        } catch (...) {
+            return checkFail("Failed obtaining the nixpkgs version: nixpkgs is either broken or invalid");
+        }
+
         return true;
     }
 

tests/functional/remote-store.sh

@@ -2,9 +2,6 @@ source common.sh
 
 clearStore
 
-# Ensure "fake ssh" remote store works just as legacy fake ssh would.
-nix --store ssh-ng://localhost?remote-store=$TEST_ROOT/other-store doctor
-
 # Ensure that store ping trusted works with ssh-ng://
 nix --store ssh-ng://localhost?remote-store=$TEST_ROOT/other-store store ping --json | jq -e '.trusted'
 

tests/functional2/cli/test_doctor.py

@@ -0,0 +1,39 @@
+from testlib.fixtures.nix import Nix
+import pytest
+
+
+pytestmark = pytest.mark.no_daemon
+
+
+@pytest.mark.usefixtures("fake_nixpkgs")
+def test_doctor_local_store(nix: Nix):
+    res = nix.nix(["doctor", "-v"]).run().ok()
+    out = res.stderr_plain
+    assert "[PASS] All profiles are gcroots." in out
+    assert "[PASS] Client protocol matches store protocol." in out
+    assert "You are trusted" in out
+    assert "[FAIL] Error: current generation cannot be discovered" in out
+
+
+@pytest.mark.usefixtures("fake_nixpkgs")
+def test_doctor_remote_store(nix: Nix):
+    res = (
+        nix.nix(
+            [
+                "--store",
+                f"ssh-ng://localhost?remote-store={nix.env.dirs.test_root}/other-store",
+                "doctor",
+            ]
+        )
+        .run()
+        .ok()
+    )
+    assert "Running checks against store uri ssh-ng://localhost" in res.stderr_plain
+
+
+@pytest.mark.usefixtures("fake_nixpkgs")
+def test_doctor_nixpkgs(nix: Nix):
+    res = nix.nix(["doctor", "-v"], flake=True).run().ok()
+    out = res.stderr_plain
+
+    assert "[INFO] Nixpkgs provenance: nixpkgs=" in out

tests/functional2/store/test_local_store.py

@@ -39,6 +39,7 @@ class TestLocalStore:
         info = nix.nix(["--store", "./x", "store", "ping", "--json"]).run().json()
         assert info["trusted"]
 
+    @pytest.mark.usefixtures("fake_nixpkgs")
     def test_doctor_shows_trust(self, nix: Nix):
         result = nix.nix(["--store", "./x", "doctor"]).run().ok()
         assert "You are trusted by" in result.stderr_plain