From d1179f12ece440734f3e943c439ed9657b2b691b Mon Sep 17 00:00:00 2001
From: Spencer Brower <6729162+sbrow@users.noreply.github.com>
Date: Wed, 5 Aug 2026 18:01:31 -0400
Subject: [PATCH] feat: Mis-spelled extension names now show up as hints.

---
 AGENTS.md              |  2 +-
 TODOS.md               |  5 +++--
 markdown/markdown.odin | 28 +++++++++++++++++++++++++---
 site/thor.json         |  3 ++-
 4 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/AGENTS.md b/AGENTS.md
index cb41f00..8bdf15d 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -73,7 +73,7 @@ thor/
 | Package | Files | Responsibility |
 |---|---|---|
 | `treesitter/` | `treesitter.odin` | FFI types (`Parser`, `Node`, `Query`, etc.), `@(link_prefix="ts_")` foreign bindings, grammar management (`Grammar_Store` with persistent allocator, `load_language`/`compile_query` building blocks, `ensure_parser`/`load_grammar` lazy loading, `preload_grammar`/`preload_grammars` for parallel loading with `sync.Mutex` cache protection), statically-linked HTML/CSS grammars |
-| `markdown/` | `markdown.odin` | `Extension` enum, `DEFAULT_EXTENSIONS`, `process(body, ext, file_path, allocator)` — full pipeline (clones cmark output, frees original), `parse_extension_list`, `apply_extension_config` |
+| `markdown/` | `markdown.odin` | `Extension` enum, `DEFAULT_EXTENSIONS`, `EXTENSION_NAMES`, `process(body, ext, file_path, allocator)` — full pipeline (clones cmark output, frees original), `parse_extension_list` (with "did you mean?" hints via `diagnostics.suggest_correction`), `apply_extension_config` (same), `resolve_extension_conflicts` (Footnotes wins over Sidenotes) |
 | | `footnotes.odin` | `strip_definitions` (pre-cmark, shared by `.Sidenotes` + `.Footnotes`), `inject_notes` (post-cmark sidenote rendering), `inject_footnotes` (post-cmark standard footnote rendering — numbered `<sup>` links + `<section class="footnotes"><ol>` at bottom). `.Sidenotes` and `.Footnotes` are mutually exclusive; `resolve_extension_conflicts` in `markdown.odin` picks `.Footnotes` if both are set. |
 | | `alerts.odin` | `inject_alerts` — GitHub alert blocks (`> [!NOTE]`) → styled blockquotes with semantic class names (`alert-note` etc.) |
 | | `emoji.odin` | `expand_emoji` — `:shortcode:` → unicode emoji |
diff --git a/TODOS.md b/TODOS.md
index 5ff8a72..653c023 100644
--- a/TODOS.md
+++ b/TODOS.md
@@ -13,8 +13,9 @@
 - [ ] [aliases](https://gohugo.io/methods/page/aliases/#redirects)?
 - [ ] Improve diagnostics
   - [x] keep track of every error and don't report them more than once.
-  - [ ] show parsed arg when -extension is unrecognized 
-    - [ ] also do typo detection?
+  - [x] show parsed arg when -extension is unrecognized 
+    - [x] also do typo detection?
+    - [ ] show where the typo occurred (config file path for `apply_extension_config`, full `-ext:value` for `parse_extension_list`)
   - [ ] `*` make sure the frontmatter parser has good diagnostics.
   - [ ] fix the diagnostics in [DIAGNOSTIC TODOS](./DIAGNOSTIC_TODOS.yaml)
   - [ ] only report format errors once.
diff --git a/markdown/markdown.odin b/markdown/markdown.odin
index 0b210f8..fa1127c 100644
--- a/markdown/markdown.odin
+++ b/markdown/markdown.odin
@@ -6,6 +6,8 @@ import "core:encoding/json"
 import "core:log"
 import "core:strings"
 
+import diags "../diagnostics"
+
 Extension :: enum {
 	Emoji,
 	Sidenotes,
@@ -19,6 +21,11 @@ Extension :: enum {
 
 DEFAULT_EXTENSIONS :: bit_set[Extension]{.Emoji, .Sidenotes, .Alerts, .HeadingIDs, .DefLists}
 
+EXTENSION_NAMES :: []string{
+	"emoji", "sidenotes", "alerts", "highlight", "sections",
+	"heading_ids", "deflists", "footnotes",
+}
+
 // Caller is responsible for freeing string
 process :: proc(
 	body: string,
@@ -69,7 +76,12 @@ parse_extension_list :: proc(s: string) -> (result: bit_set[Extension]) {
 		e, ok := extension_from_name(name)
 		if !ok {
 			if name != "" {
-				log.warnf("unknown extension '%s'", name)
+				suggestion := diags.suggest_correction(EXTENSION_NAMES, name)
+				if suggestion != "" {
+					log.warnf("unknown extension '%s' (did you mean '%s'?)", name, suggestion)
+				} else {
+					log.warnf("unknown extension '%s'", name)
+				}
 			}
 			continue
 		}
@@ -81,9 +93,19 @@ parse_extension_list :: proc(s: string) -> (result: bit_set[Extension]) {
 // Given a map[Extension]bool, apply it to ext.
 apply_extension_config :: proc(ext: ^bit_set[Extension], config: json.Object) {
 	for name, val in config {
-		// TODO: Silently discards invalid values.
 		enabled := val.(json.Boolean) or_continue
-		e := extension_from_name(name) or_continue
+
+		e, ok := extension_from_name(name)
+		if !ok {
+			lower := strings.to_lower(name, context.temp_allocator)
+			suggestion := diags.suggest_correction(EXTENSION_NAMES, lower)
+			if suggestion != "" {
+				log.warnf("unknown extension '%s' (did you mean '%s'?)", name, suggestion)
+			} else {
+				log.warnf("unknown extension '%s'", name)
+			}
+			continue
+		}
 
 		if enabled {
 			ext^ += {e}
diff --git a/site/thor.json b/site/thor.json
index dc2f8ee..32708cb 100644
--- a/site/thor.json
+++ b/site/thor.json
@@ -1,6 +1,7 @@
 {
   "markdown_extensions": {
-    "footnotes": true
+    // "footnotes": true
+    "foonotes": true
   },
   "params": {
     "author": {