# Elixir Code Smell Analysis — bDS2 > Generated by static analysis of the codebase. Do not delete; use as a reference for refactoring sprints. > > **Updated 2026-04-30:** Each claim re-verified against current code. See "Verification Summary" and "Priority Order" sections at the bottom. --- ## Summary The project is architecturally sound at a high level: contexts are well-defined, Ecto is used properly for schema validation, `with` blocks handle errors cleanly, and the GenServer implementations are mostly correct. However, **the codebase suffers from severe module bloat, excessive duplication of helper functions, risky process-dictionary usage, and several side-effect-in-transaction anti-patterns** that become maintenance liabilities in a desktop application expected to run for long sessions. --- ## Critical Anti-Patterns ### 1. Massive Module Bloat (Most Serious) Several modules are far too large and violate the single-responsibility principle. | Module | Lines | Issue | |--------|-------|-------| | `BDS.Desktop.ShellLive` | 2,607 | Handles UI events, routing, overlays, menus, project switching, tab management, translations, task polling, and native menu integration | | `BDS.Posts` | 1,709 | Handles CRUD, publishing, file I/O, translations, auto-translation scheduling, embeddings sync, search sync, link rebuilding, and validation | | `BDS.Generation` | 2,624 | Site generation, validation, sitemap building, archive pagination, feed rendering, and file hashing (verified larger than originally documented) | | `BDS.MCP` | 670 | MCP tools, resources, proposals, post detail serialization, search, and category counting | | `BDS.Media` | 939 | Media CRUD, thumbnail generation, sidecar I/O, post-media join management | **Why this is an anti-pattern:** Giant modules reduce compiler concurrency, make refactoring dangerous, obscure test coverage, and increase merge conflicts. Elixir/OTP best practice is to keep modules under ~400 lines and split by responsibility. **Fix:** Extract sub-domains into dedicated modules (e.g., `BDS.Posts.Publisher`, `BDS.Posts.Translations`, `BDS.Generation.SitemapBuilder`, `BDS.Desktop.ShellLive.EventRouter`). --- ### 2. Process Dictionary for I18n State (and 13 other call sites across all `*_editor.ex` modules — 15 total) In `BDS.Desktop.ShellLive`: ```elixir def render(assigns) do Process.put(:bds_ui_locale, assigns.page_language) index(assigns) end ``` And later: ```elixir defp translated(text, bindings \\ %{}), do: ShellData.translate(text, bindings, Process.get(:bds_ui_locale)) ``` **Why this is an anti-pattern:** The process dictionary is implicit global state. It makes functions harder to test in isolation and can leak state between concurrent operations in the same process. Elixir strongly discourages `Process.put/get` for business logic. **Fix:** Pass `locale` explicitly through `assigns` to all translation call sites, or use a dedicated context struct. --- ### 3. Side Effects Inside Database Transactions (7 transactions in `lib/bds/media.ex` follow this pattern) In `BDS.Media.import_media/1`: ```elixir Repo.transaction(fn -> media = %Media{} |> Media.changeset(...) |> Repo.insert!() :ok = File.mkdir_p(Path.dirname(destination)) :ok = File.cp(source_path, destination) :ok = write_sidecar(project, media) :ok = ensure_thumbnails(project, media) :ok = Search.sync_media(media) media end) ``` **Why this is an anti-pattern:** If the transaction retries (or the DB connection times out in SQLite), filesystem and thumbnail side effects are duplicated or orphaned. Ecto transactions should contain **only** database operations. **Fix:** Perform the DB insert in the transaction, then do filesystem work after the transaction succeeds. --- ### 4. `String.to_atom/1` on Untrusted Input In `BDS.MCP`: ```elixir defp atomize_keys(map) when is_map(map) do Map.new(map, fn {key, value} -> {String.to_atom(key), value} end) end ``` **Why this is an anti-pattern:** Atoms are not garbage collected. If MCP receives large or arbitrary JSON keys, the VM atom table can fill up and crash the BEAM. **Fix:** Use `String.to_existing_atom/1` (with a safe fallback) or keep keys as strings. Note: 10 other `String.to_atom` call sites exist, but they operate on bounded enums (modality, platform, view id) and are lower risk. --- ### 5. Bang Functions (`File.read!`) in Business Logic Without Rescue Found in `BDS.Posts`, `BDS.Media`, `BDS.MCP`, `BDS.Generation`: ```elixir defp parse_rebuild_file(project, path) do contents = File.read!(path) {:ok, %{fields: fields}} = Frontmatter.parse_document(contents) ... end ``` **Why this is an anti-pattern:** Missing files or permission errors raise unhandled exceptions that crash the caller Limit the change to files reached from long-running processes; mandatory configuration files can stay as `File.read!`.. In a GenServer context (e.g., background tasks), this brings down the worker. **Fix:** Use `File.read/1` and handle `{:error, reason}` explicitly, returning `{:error, reason}` tuples to callers. --- ### 6. Duplicate Helper Functions Across Contexts The same private helpers are copy-pasted in `BDS.Posts`, `BDS.Media`, `BDS.Search`, `BDS.Generation`, `BDS.Publishing`, `BDS.MCP`: - `attr/2` (atom/string key normalization) - `maybe_put/3` - `blank_to_nil/1` - `progress_callback/1` - `report_rebuild_started/3`, `report_rebuild_progress/4` **Why this is an anti-pattern:** Violates DRY. When behavior needs to change (e.g., adding float progress support), every copy must be updated. **Fix:** Extract to a shared utility module such as `BDS.MapUtils`, `BDS.AttrUtils`, or `BDS.ProgressReporter`. --- ### 7. Direct Repo Access in LiveView (10 sites verified) `BDS.Desktop.ShellLive` directly queries the repo: ```elixir case Repo.get(Post, post_id) do %Post{} = post -> ... end ``` **Why this is an anti-pattern:** LiveViews are the web layer; they should call context functions (`BDS.Posts.get_post/1`). Direct Repo access leaks persistence details into the UI and makes testing harder. **Fix:** Replace all `Repo.get` calls in `ShellLive` with context function calls. --- ### 8. `String.to_existing_atom/1` on User Input Without Whitelist In `ShellLive`: ```elixir def handle_event("select_view", %{"view" => view_id}, socket) do workbench = Workbench.click_activity(socket.assigns.workbench, String.to_existing_atom(view_id)) ... end ``` **Why this is an anti-pattern:** If a client sends a non-existent atom string, it raises `ArgumentError`. While safer than `to_atom`, it is still a crash vector. **Fix:** Validate against a whitelist or map of known string-to-atom conversions before conversion. --- ### 9. Nested Exception Handling for Control Flow In `ShellLive`: ```elixir defp safe_existing_atom(action) when is_binary(action) do String.to_existing_atom(action) rescue ArgumentError -> nil end ``` **Why this is an anti-pattern:** Using exceptions for expected control flow is slower and harder to follow than explicit validation. **Fix:** Maintain an explicit mapping of allowed actions, or use a `case` with `:erlang.binary_to_existing_atom/2` and catch the error tuple. --- ### 10. `Jason.decode!` Without Err and `BDS.AI` (HTTP-response decoding)or Handling In `BDS.AI.OpenAICompatibleRuntime`: ```elixir defp normalize_response(body) do payload = Jason.decode!(body) ... end ``` **Why this is an anti-pattern:** Malformed JSON from an externa Limit the change to HTTP-response decoding; decoding of our own on-disk files (`metadata.ex`, `embeddings/index.ex`, etc.) is acceptable. --- ## Moderate Concerns ### 11. Missing `@spec` Typespecs Verified: only **10 `@spec` declarations across all of `lib/`**, and they are concentrated in `BDS.Scripting` / `BDS.Scripting.Lua`. Every other public context function relies on Dialyzer inference. For a project of this size, adding `@spec` to public APIs is the single highest-ROI type-safety improvement available — and pairs well with the existing `mix dialyzer --format short` check. ### 12. Tests Run Synchronously Most tests use `use ExUnit.Case, async: false`. Many tests share the SQLite repo and named GenServers, so they cannot realistically be async. Limit conversion to pure-logic test files (parsers, formatters, etc.). ### 13. Raw SQL Overuse 19 `Repo.query` sites split into two groups: 1. **FTS5 virtual tables** in `BDS.Search` (`posts_fts`, `media_fts`, `MATCH`, `bm25`, `rank`). Ecto cannot express FTS5 queries cleanly. **Keep these raw.** 2. **`post_media` join table** queried by hand in `BDS.Posts`, `BDS.Media`, `BDS.Desktop.ShellLive.OverlayComponents`, `BDS.Desktop.ShellLive.PostEditor`. There is no `BDS.PostMedia` schema. This is the real type-safety hole; introducing the schema replaces 6–8 raw queries with Ecto While SQLite FTS necessitates some raw SQL, many queries in `BDS.Search`, `BDS.Media`, and `BDS.Posts` use `Repo.query!/2` for standard operations that Ecto could express portably (e.g., `DELETE FROM ... WHERE ...`). This reduces type safety and database portability. ### 14. Atom/String Key Duality Many functions normalize between atom and string keys repeatedly: ```elixir Map.get(assigns, :language, Map.get(assigns, "language", ...)) ``` This suggests data isn't normalized at boundaries. Prefer atoms for internal structs and strings only at external boundaries (JSON, HTTP params). ### 15. GenServer State Growth (Tasks) `BDS.Tasks` stores all tasks forever in a single map. The `clear_completed`/`clear_finished` functions exist, but if the UI doesn't trigger them regularly in a long-running desktop app, memory grows unbounded. Consider TTL-based eviction. --- ## What the Project Does Well - **Contexts are clearly separated** (`Posts`, `Media`, `Projects`, `Search`, etc.). - **Ecto changesets** are used consistently for validation. - **`with` blocks** handle multi-step error flows cleanly. - **Pattern matching** is idiomatic and pervasive. - **Task.Supervisor** is used correctly for background work. - *Verification Summary (2026-04-30) | # | Claim | Verified | Notes | |---|---|---|---| | 1 | Module bloat | ✅ | `Generation` is 2624 lines, worse than originally documented. | | 2 | `Process.put(:bds_ui_locale)` | ✅ | 15 call sites across `shell_live.ex` and every `*_editor.ex`. | | 3 | Side effects in transactions | ✅ | 7 transactions in `lib/bds/media.ex` wrap filesystem + Search side effects. | | 4 | `String.to_atom` on untrusted input | ⚠️ Partly | Only `MCP.atomize_keys` is on arbitrary external JSON. Other 10 sites are bounded enums. | | 5 | `File.read!` | ⚠️ Partly | Most sites read mandatory config; only loop/background paths are real risk. | | 6 | Duplicated helpers | ✅ | Real DRY violation across contexts. | | 7 | `Repo.get` in `ShellLive` | ✅ | 10 direct calls. | | 8/9 | `to_existing_atom` + rescue | ⚠️ | The rescue effectively *is* the whitelist; cosmetic priority. | | 10 | `Jason.decode!` on external responses | ⚠️ Partly | Only 2 of 14 sites decode HTTP responses; the rest decode our own files. | | 11 | Missing `@spec` | ✅ | 10 specs in entire `lib/`. Highest type-safety ROI. | | 12 | Tests synchronous | ✅ | Limited convertibility — most tests share repo/GenServers. | | 13 | Raw SQL | ⚠️ Partly | FTS5 must stay raw; `post_media` table is the real fix target. | --- ## Priority Order 1. **Add `@spec` to public APIs of core contexts.** ✅ **DONE 2026-04-30.** See "Priority #1 Completion" section below. 2. **Extract filesystem / Search side effects out of `Repo.transaction` in `BDS.Media`.** ✅ **DONE 2026-04-30.** See "Priority #2 Completion" section below. 3. **Fix `MCP.atomize_keys`** to use `String.to_existing_atom/1` with a string-fallback. ✅ **DONE 2026-04-30.** See "Priority #3 Completion" section below. 4. **Introduce `BDS.PostMedia` Ecto schema** and migrate the 6–8 raw `post_media` queries. Direct type-safety win. 5. **Replace `Repo.get` calls in `ShellLive`** with context functions (add new context functions where needed). 6. **Move locale from `Process.put` into assigns**, then ban `Process.put` via Credo. 7. **Extract shared helpers** (`attr/2`, `maybe_put/3`, `blank_to_nil/1`, `progress_callback/1`, rebuild progress reporters) into `BDS.MapUtils` / `BDS.ProgressReporter`. 8. **Wrap external `Jason.decode!` calls** in `BDS.AI.OpenAICompatibleRuntime` and `BDS.AI` with `Jason.decode/1` + `{:error, _}` propagation. 9. **Module split.** `BDS.Generation` (2624) and `BDS.Desktop.ShellLive` (2607) first; schedule each as its own sprint. ### Skipped / downgraded - #5 in bulk — convert only paths reached from long-running processes. - #8 / #9 — cosmetic; the rescue functions as a whitelist today. - #12 — leave `async: false` where the repo or named GenServers are involved. - #15 — bounded in practice; ensure UI triggers `clear_finished` periodically. --- ## Bottom Line The biggest risks are **module size** and **duplicated helpers**, followed by the **process dictionary i18n** and **side effects in transactions**. The single highest-ROI improvement for type safety is **adding `@spec` to public context APIs** so Dialyzer can do its job — that is the starting point of the priority order above --- ## Priority #1 Completion (2026-04-30) Added `@spec` and `@type` declarations to the public APIs of all core contexts and their schemas. Validation: `mix compile --warnings-as-errors` clean, `mix dialyzer --format short` 0 errors, `mix test` 342/0/4. **Files modified (specs added):** - `lib/bds/projects.ex`, `lib/bds/projects/project.ex` - `lib/bds/posts.ex`, `lib/bds/posts/post.ex`, `lib/bds/posts/translation.ex`, `lib/bds/posts/link.ex` - `lib/bds/media.ex`, `lib/bds/media/media.ex`, `lib/bds/media/translation.ex` - `lib/bds/search.ex` - `lib/bds/publishing.ex`, `lib/bds/publishing/publish_job.ex` - `lib/bds/generation.ex` - `lib/bds/metadata.ex` - `lib/bds/mcp.ex` - `lib/bds/ai.ex` **Bugs surfaced and fixed by Dialyzer once specs were in place:** - `BDS.Search.list_stemmer_languages/0` returns `[String.t()]`, not `[{String.t(), [String.t()]}]`. - `BDS.Media.sync_media_sidecar/1` returns `:ok` (not `{:ok, t()}`); the `posts.ex` caller was already pattern-matching on `:ok`. - `BDS.Media.replace_media_file/2` can return `{:ok, nil}` when the new file's checksum is unchanged. - Removed unreachable `other -> {:error, other}` fall-through clauses in the auto-translate cascades in `BDS.Posts` (the preceding `{:error, reason}` pattern already covers the only remaining return shape). - Removed unreachable `defp blank?(_value)` clause in `BDS.Desktop.ShellLive.ChatEditor` (prior clauses already covered `binary` and `nil`, no other types reach the function). **Conventions established for future spec work:** - Ecto schemas need explicit `@type t` — Ecto does not generate one. - Use `term()` for `belongs_to` / `has_many` association fields to avoid circular type dependencies between sibling schemas. - Use `@typedoc` + named types (e.g. `attrs`, `metadata_state`, `search_filters`, `reindex_opts`) to avoid repeating large map shapes across many specs in the same module. - For `update_*` / attrs-style maps, the canonical type is `%{optional(atom()) => term(), optional(String.t()) => term()}` because both renderer-supplied string keys and Elixir atom keys flow into them. **Not yet specced (intentional, out of scope of priority #1):** - LiveView modules under `lib/bds/desktop/shell_live/`. These are Phoenix LiveView callbacks (`mount/3`, `handle_event/3`, `handle_info/2`) whose specs are inherited from the behaviour. Public helper functions in those modules can be specced as part of the eventual ShellLive module split (priority #9). - Internal helpers in `BDS.MCP` and `BDS.AI` that are private (`defp`) — Dialyzer infers these. - `BDS.Tags`, `BDS.Templates`, `BDS.Scripts`, `BDS.PostLinks` — smaller contexts; queue for a follow-up pass if Dialyzer surfaces issues. --- ## Priority #2 Completion (2026-04-30) Refactored every `Repo.transaction/1` block in [lib/bds/media.ex](lib/bds/media.ex) so that only DB writes run inside the transaction. Filesystem writes (`File.cp`, `write_sidecar`, `write_translation_sidecar`, `ensure_thumbnails`, `delete_file_if_present`) and `Search.sync_media/1` calls now run *after* the transaction commits, so the SQLite write lock is released as fast as possible. **Functions refactored:** - `import_media/1` — copies the source file into place *before* the transaction (so a DB rollback can still observe a stale file), then runs only the `Repo.insert!` inside the transaction, then writes sidecar / thumbnails / search index. On DB failure the copied file is removed. - `update_media/2` — DB update only inside the transaction; sidecar + search after. - `upsert_media_translation/3` — DB insert/update only inside; sidecar + search after. - `delete_media_translation/2` — DB delete only inside; sidecar deletion + search reindex + base sidecar rewrite after. - `replace_media_file/2` — moves the existing destination to a `.bak` *before* the transaction, copies the new file in place, runs only the DB update inside, then refreshes sidecar/thumbnails/search and removes the backup. On DB failure the original file is restored from the backup. - `link_media_to_post/2` and `unlink_media_from_post/2` — only the `post_media` raw INSERT/DELETE runs inside the transaction; sidecar rewrite happens after commit. **Why this matters:** SQLite has a single global write lock. Holding the transaction open while we copy files, regenerate Vix-backed thumbnails, and rebuild FTS5 indices makes that lock-hold time unbounded and proportional to image size. Other actors (the LiveView, background tasks, the CLI sync watcher) hit `:busy` retries that the existing `db_connection` busy-timeout cannot always cover. After this change the lock is held for milliseconds, regardless of file size. **Trade-offs accepted:** - The DB row and the filesystem are no longer atomically coupled. If the BEAM crashes between `Repo.insert!` and `write_sidecar/2`, the row exists without a sidecar. This is recoverable by the existing rebuild-from-database path (which re-emits sidecars), and is the same trade-off that exists everywhere else in the codebase that already runs side effects after transactions. - `import_media/1` and `replace_media_file/2` use the inverse approach — file IO *before* transaction with explicit cleanup on rollback — because the file is the larger of the two side effects and the DB row is a pointer to it. This keeps the destination consistent on rollback. **Spec correction surfaced by Dialyzer:** - `BDS.Media.delete_media_translation/2` actually returns `{:ok, boolean()} | {:error, :not_found | term()}` (the `:ok` payload is `false` when no translation exists for the language, `true` when one was deleted). The previous spec advertised `{:ok, :deleted}`, which never matched any code path. **Validation:** `mix compile --warnings-as-errors` clean, `mix dialyzer --format short` 0 errors, `mix test` 342/0/4. --- ## Priority #3 Completion (2026-04-30) Removed `BDS.MCP.atomize_keys/1` entirely instead of just narrowing it to `String.to_existing_atom/1`. The function existed only to convert MCP-proposal JSON keys (attacker-controlled strings) into atoms before passing them to `Media.update_media/2` and `Posts.update_post/2`. Both contexts already accept string-keyed maps natively through their `attr/2` helper (`%{optional(atom()) => term(), optional(String.t()) => term()}`), so the conversion was both unnecessary and a textbook unbounded-atom-table DoS vector. **Change:** - Deleted `defp atomize_keys/1` from [lib/bds/mcp.ex](lib/bds/mcp.ex). - The two `accept_proposal` call sites now pass `proposal.data["changes"] || %{}` straight through to `Media.update_media/2` and `Posts.update_post/2`. **Why removal beats whitelisting:** - `String.to_existing_atom/1` would still need a whitelist or a `try/rescue` wrapper, both of which add code without buying type safety — the downstream contexts already key on either form. - Removing the function eliminates the only place in MCP that converts external JSON to atoms; the surface area for atom-table attacks via the MCP tool API is now zero. - The `attr/2` helpers in `BDS.Posts` and `BDS.Media` are the *single* canonical place where attribute key normalization happens, which is exactly the invariant we want. **Other `String.to_atom/1` call sites considered:** The codebase has nine other `String.to_atom/1` call sites; all of them operate on bounded inputs (`Workbench` type names, release platforms, route IDs from the router config, `:supports_attachment` / `:supports_tool_calls` capability keys we ourselves wrote, `parse_modality` from a fixed AI catalog). None of them are reachable from attacker-controlled JSON the way `MCP.accept_proposal` was. They are safe to leave as a follow-up if a stricter sweep is wanted later. **Validation:** `mix compile --warnings-as-errors` clean, `mix dialyzer --format short` 0 errors, `mix test` 342/0/4. --- ## Bottom Line The biggest risks are **module size** and **duplicated helpers**, followed by the **process dictionary i18n** and **side effects in transactions**. Fixing the top 5 anti-patterns would significantly improve maintainability, testability, and reliability of the desktop app over long-running sessions.