From 1bc2ebd775a0e88f5f58b7040215fb0daee41a1a Mon Sep 17 00:00:00 2001
From: Gabor Szabo <gabor@szabgab.com>
Date: Fri, 28 Mar 2025 10:56:41 +0300
Subject: [PATCH 1/2] warn on invalid fields in root of book.toml

---
 src/config.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/config.rs b/src/config.rs
index 905020a39c..f4eab9688c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -312,6 +312,8 @@ impl<'de> serde::Deserialize<'de> for Config {
             return Ok(Config::from_legacy(raw));
         }
 
+        warn_on_invalid_fields(&raw);
+
         use serde::de::Error;
         let mut table = match raw {
             Value::Table(t) => t,
@@ -376,6 +378,20 @@ fn parse_env(key: &str) -> Option<String> {
         .map(|key| key.to_lowercase().replace("__", ".").replace('_', "-"))
 }
 
+fn warn_on_invalid_fields(table: &Value) {
+    let valid_items = ["book", "build", "rust", "output", "preprocessor"];
+
+    if let Some(table) = table.as_table() {
+        for item in table.keys() {
+            if !valid_items.contains(&item.as_str()) {
+                warn!("Invalid field {:?} in book.toml", &item);
+            }
+        }
+    } else {
+        warn!("Invalid format in book.toml");
+    }
+}
+
 fn is_legacy_format(table: &Value) -> bool {
     let legacy_items = [
         "title",

From 97f19486817726965e6c4b9b9839dae0b5893f30 Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Thu, 3 Apr 2025 11:17:25 -0700
Subject: [PATCH 2/2] Make the unexpected case explicit that it is an internal
 error

The current code has the `else` clause as unreachable, and the text it
has isn't clear that is the case.
---
 src/config.rs | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/config.rs b/src/config.rs
index f4eab9688c..db159a45ad 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -381,14 +381,11 @@ fn parse_env(key: &str) -> Option<String> {
 fn warn_on_invalid_fields(table: &Value) {
     let valid_items = ["book", "build", "rust", "output", "preprocessor"];
 
-    if let Some(table) = table.as_table() {
-        for item in table.keys() {
-            if !valid_items.contains(&item.as_str()) {
-                warn!("Invalid field {:?} in book.toml", &item);
-            }
+    let table = table.as_table().expect("root must be a table");
+    for item in table.keys() {
+        if !valid_items.contains(&item.as_str()) {
+            warn!("Invalid field {:?} in book.toml", &item);
         }
-    } else {
-        warn!("Invalid format in book.toml");
     }
 }