improve error management with thiserror use

- add thiserror dependency
- use distinct Error enum in lib and server

src/lib.rs

@@ -36,10 +36,11 @@
 //! println!("RESULT = {:#?}", res);
 //! ```
 
+use thiserror::Error;
+
 #[cfg(feature = "embedded-server")]
 use crate::server::EmbeddedServer;
 use std::collections::HashMap;
-use std::error::Error;
 
 #[cfg(feature = "embedded-server")]
 pub mod server;
@@ -302,6 +303,28 @@ pub struct SuggestResult {
     pub suggestions: Vec<String>,
 }
 
+#[derive(Debug, Error)]
+pub enum Error {
+    #[cfg(feature = "embedded-server")]
+    #[error("Grammalecte-server failed to start")]
+    ServerStartFailed(#[from] server::Error),
+
+    #[error("Failed to Serialize Option in Json")]
+    OptionJsonSerialization(#[source] serde_json::Error),
+
+    #[error("Failed to send request `check with option`")]
+    RequestSendCheckWithOptions(#[source] reqwest::Error),
+
+    #[error("Failed to send request `suggest`")]
+    RequestSendSuggest(#[source] reqwest::Error),
+
+    #[error("Failed to Deserialize Check result")]
+    CheckResultDeserialize(#[source] reqwest::Error),
+
+    #[error("Failed to Deserialize Suggest result")]
+    SuggestDeserialize(#[source] reqwest::Error),
+}
+
 /// The Grammalecte client itself
 pub struct GrammalecteClient {
     base_url: String,
@@ -335,7 +358,7 @@ impl GrammalecteClient {
     ///
     /// Python 3.7 or higher must is required at runtime
     #[cfg(feature = "embedded-server")]
-    pub fn start_server() -> Result<Self, Box<dyn Error>> {
+    pub fn start_server() -> Result<Self, Error> {
         let server = EmbeddedServer::start()?;
         Ok(Self {
             base_url: server.base_url(),
@@ -344,7 +367,7 @@ impl GrammalecteClient {
     }
 
     /// Run spell check on text
-    pub async fn spell_check(&self, text: &str) -> Result<CheckResult, Box<dyn Error>> {
+    pub async fn spell_check(&self, text: &str) -> Result<CheckResult, Error> {
         self.spell_check_with_options(text, &HashMap::new()).await
     }
 
@@ -353,7 +376,7 @@ impl GrammalecteClient {
         &self,
         text: &str,
         options: &HashMap<GramOpt, bool>,
-    ) -> Result<CheckResult, Box<dyn Error>> {
+    ) -> Result<CheckResult, Error> {
         let url = format!("{}/gc_text/fr", self.base_url);
         log::debug!("Will use URL {} for spell check", url);
 
@@ -361,7 +384,7 @@ impl GrammalecteClient {
             .iter()
             .map(|t| (t.0.id(), t.1))
             .collect::<HashMap<_, _>>();
-        let options = serde_json::to_string(&options)?;
+        let options = serde_json::to_string(&options).map_err(Error::OptionJsonSerialization)?;
 
         let mut params = HashMap::new();
         params.insert("text", text);
@@ -371,28 +394,32 @@ impl GrammalecteClient {
             .post(url)
             .form(&params)
             .send()
-            .await?
+            .await
+            .map_err(Error::RequestSendCheckWithOptions)?
             .json::<CheckResult>()
-            .await?;
+            .await
+            .map_err(Error::CheckResultDeserialize)?;
 
         Ok(result)
     }
 
     /// Ask for word suggestion
-    pub async fn suggest(&self, token: &str) -> Result<SuggestResult, Box<dyn Error>> {
+    pub async fn suggest(&self, token: &str) -> Result<SuggestResult, Error> {
         let url = format!("{}/suggest/fr", self.base_url);
         log::debug!("Will use URL {} for word suggestion", url);
 
         let mut params = HashMap::new();
         params.insert("token", token);
 
-        Ok(reqwest::Client::new()
+        reqwest::Client::new()
             .post(&url)
             .form(&params)
             .send()
-            .await?
+            .await
+            .map_err(Error::RequestSendSuggest)?
             .json()
-            .await?)
+            .await
+            .map_err(Error::SuggestDeserialize)
     }
 }