UnkeyedValidPathInfo::fromJSON Remove support for older version

It turns out this code path is only used for unit tests (to ensure our
JSON formats are possible to parse by other code, elsewhere). No
user-facing functionality consumes this format.

Therefore, let's drop the old version parsing support.

Author: Ericson2314

doc/manual/rl-next/json-format-changes.md

@@ -22,7 +22,7 @@ The store path info JSON format has been updated from version 1 to version 2:
   - New: `"ca": {"method": "nar", "hash": {"algorithm": "sha256", "format": "base64", "hash": "EMIJ+giQ..."}}`
   - Still `null` values for input-addressed store objects
 
-Version 1 format is still accepted when reading for backward compatibility.
+Nix currently only produces, and doesn't consume this format.
 
 **Affected command**: `nix path-info --json`
 

src/libstore/derivation-options.cc

@@ -423,15 +423,6 @@ void adl_serializer<DerivationOptions>::to_json(json & json, const DerivationOpt
     json["allowSubstitutes"] = o.allowSubstitutes;
 }
 
-template<typename T>
-static inline std::optional<T> ptrToOwned(const json * ptr)
-{
-    if (ptr)
-        return std::optional{*ptr};
-    else
-        return std::nullopt;
-}
-
 DerivationOptions::OutputChecks adl_serializer<DerivationOptions::OutputChecks>::from_json(const json & json_)
 {
     auto & json = getObject(json_);

src/libstore/path-info.cc

@@ -192,13 +192,10 @@ UnkeyedValidPathInfo UnkeyedValidPathInfo::fromJSON(const StoreDirConfig & store
 
     auto & json = getObject(_json);
 
-    // Check version (optional for backward compatibility)
-    nlohmann::json::number_unsigned_t version = 1;
-    if (json.contains("version")) {
-        version = getUnsigned(valueAt(json, "version"));
-        if (version != 1 && version != 2) {
-            throw Error("Unsupported path info JSON format version %d, expected 1 through 2", version);
-        }
+    {
+        auto version = getUnsigned(valueAt(json, "version"));
+        if (version != 2)
+            throw Error("Unsupported path info JSON format version %d, only version 2 is currently supported", version);
     }
 
     res.narHash = Hash::parseAny(getString(valueAt(json, "narHash")), std::nullopt);
@@ -213,19 +210,12 @@ UnkeyedValidPathInfo UnkeyedValidPathInfo::fromJSON(const StoreDirConfig & store
         throw;
     }
 
-    // New format as this as nullable but mandatory field; handling
-    // missing is for back-compat.
-    if (auto * rawCa0 = optionalValueAt(json, "ca"))
-        if (auto * rawCa = getNullable(*rawCa0))
-            switch (version) {
-            case 1:
-                // old string format also used in SQLite DB and .narinfo
-                res.ca = ContentAddress::parse(getString(*rawCa));
-                break;
-            case 2 ... std::numeric_limits<decltype(version)>::max():
-                res.ca = *rawCa;
-                break;
-            }
+    try {
+        res.ca = ptrToOwned<ContentAddress>(getNullable(valueAt(json, "ca")));
+    } catch (Error & e) {
+        e.addTrace({}, "while reading key 'ca'");
+        throw;
+    }
 
     if (auto * rawDeriver0 = optionalValueAt(json, "deriver"))
         if (auto * rawDeriver = getNullable(*rawDeriver0))

src/libutil/include/nix/util/json-utils.hh

@@ -114,4 +114,13 @@ struct adl_serializer<std::optional<T>>
     }
 };
 
+template<typename T>
+static inline std::optional<T> ptrToOwned(const json * ptr)
+{
+    if (ptr)
+        return std::optional{*ptr};
+    else
+        return std::nullopt;
+}
+
 } // namespace nlohmann