fix(mod-api): silence optional dataset absence

src/mods/DatasetViews.lua

@@ -359,12 +359,11 @@ function DatasetViews:open(version)
   if type(version) ~= "string" or not GameVersion.VERSIONS[version] then
     return nil, "unknown_version"
   end
-  local inspected, reason, detail = CacheContract.inspect(version, self.fs, {
+  local inspected, reason = CacheContract.inspect(version, self.fs, {
     allowSource = true, semantic = true,
   })
   if not inspected then
     self.datasets[version] = nil
-    Logger.warn("dataset %s unavailable: %s", version, detail)
     return nil, reason
   end
   local plan, invalid = self:_preflight(version, inspected)

tests/engine/dataset_views_warning_policy.lua

@@ -0,0 +1,56 @@
+-- Optional dataset absence is a handled API result, while a previously valid
+-- view disappearing and malformed cache content remain actionable warnings.
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+local T = require("tests.modkit")
+local Fixture = require("tests.modkit.dataset_view_fixture")
+local DatasetViews = require("src.mods.DatasetViews")
+local GameVersion = require("src.core.GameVersion")
+local Logger = require("src.core.Logger")
+
+local previousWarn = Logger.warn
+local warnings = {}
+Logger.warn = function(fmt, ...)
+  warnings[#warnings + 1] = select("#", ...) > 0
+    and string.format(fmt, ...) or fmt
+end
+
+local ok, err = xpcall(function()
+  local unavailable = DatasetViews.new(T.sdk.memfs({}))
+  local unknown, unknownReason = unavailable:open("missing-version")
+  T.eq(unknown, nil, "unknown version has no view")
+  T.eq(unknownReason, "unknown_version", "unknown version returns its reason")
+  local absent, absentReason = unavailable:open("gold")
+  T.eq(absent, nil, "missing optional Gold dataset has no view")
+  T.eq(absentReason, "not_imported", "missing optional Gold returns its reason")
+  T.eq(#warnings, 0, "unknown and initially absent datasets do not warn")
+
+  local files = {}
+  Fixture.cache(files, "gold")
+  local service = DatasetViews.new(T.sdk.memfs(files))
+  local view = assert(service:open("gold"))
+  files[GameVersion.cachePrefix("gold") .. "rom-cache.complete"] = nil
+  T.eq(view.assets:path("assets/generated/missing.png"), nil,
+    "a stale view closes when its imported dataset disappears")
+  T.eq(#warnings, 1, "a previously valid view disappearing still warns")
+  T.check(warnings[1]:find("dataset gold unavailable", 1, true) ~= nil,
+    "the stale-view warning identifies the unavailable dataset")
+
+  warnings = {}
+  local malformedFiles = {}
+  Fixture.cache(malformedFiles, "gold", { pokemon = "not generated data" })
+  local malformed = assert(DatasetViews.new(T.sdk.memfs(malformedFiles)):open("gold"))
+  T.eq(#warnings, 0, "lazy open does not warn before malformed data is read")
+  T.eq(malformed.content.pokemon:get("FIXMON"), nil,
+    "malformed generated data fails closed")
+  T.eq(#warnings, 1, "malformed generated data still warns")
+  T.check(warnings[1]:find("dataset gold cache rejected", 1, true) ~= nil,
+    "the malformed-cache warning identifies cache rejection")
+  T.check(warnings[1]:find("pokemon:", 1, true) ~= nil,
+    "the malformed-cache warning keeps actionable module detail")
+end, debug.traceback)
+
+Logger.warn = previousWarn
+if not ok then error(err, 0) end
+
+T.finish("dataset_views_warning_policy")