notmuch: add show_part method.

notmuch/src/lib.rs

@@ -508,6 +508,25 @@ impl Notmuch {
         Ok(val)
     }
 
+    pub fn show_part(&self, query: &str, part: usize) -> Result<Part, NotmuchError> {
+        let slice = self.run_notmuch([
+            "show",
+            "--include-html=true",
+            "--entire-thread=true",
+            "--format=json",
+            &format!("--part={}", part),
+            query,
+        ])?;
+        // Notmuch returns JSON with invalid unicode.  So we lossy convert it to a string here an
+        // use that for parsing in rust.
+        let s = String::from_utf8_lossy(&slice);
+        let mut deserializer = serde_json::Deserializer::from_str(&s);
+        deserializer.disable_recursion_limit();
+        let val = serde::de::Deserialize::deserialize(&mut deserializer)?;
+        deserializer.end()?;
+        Ok(val)
+    }
+
     pub fn show_original(&self, id: &MessageId) -> Result<Vec<u8>, NotmuchError> {
         self.show_original_part(id, 0)
     }