improve error handling by using `error-stack` crate

Cargo.lock

@@ -268,6 +268,12 @@ dependencies = [
  "alloc-no-stdlib",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.71"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c7d0618f0e0b7e8ff11427422b64564d5fb0be1940354bfe2e0529b18a9d9b8"
+
 [[package]]
 name = "askama_escape"
 version = "0.10.3"
@@ -733,6 +739,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "error-stack"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f00447f331c7f726db5b8532ebc9163519eed03c6d7c8b73c90b3ff5646ac85"
+dependencies = [
+ "anyhow",
+ "rustc_version 0.4.0",
+]
+
 [[package]]
 name = "failure"
 version = "0.1.8"
@@ -3373,6 +3389,7 @@ dependencies = [
  "actix-files",
  "actix-web",
  "env_logger",
+ "error-stack",
  "fake-useragent",
  "handlebars",
  "log",

Cargo.toml

@@ -23,6 +23,7 @@ redis = {version="*"}
 md5 = {version="*"}
 rand={version="*"}
 once_cell = {version="*"}
+error-stack = "0.3.1"
 
 [dev-dependencies]
 rusty-hook = "^0.11.2"

src/engines/duckduckgo.rs

@@ -9,7 +9,9 @@ use scraper::{Html, Selector};
 
 use crate::search_results_handler::aggregation_models::RawSearchResult;
 
-use super::engine_models::EngineErrorKind;
+use super::engine_models::EngineError;
+
+use error_stack::{IntoReport, Report, Result, ResultExt};
 
 /// This function scrapes results from the upstream engine duckduckgo and puts all the scraped
 /// results like title, visiting_url (href in html),engine (from which engine it was fetched from)
@@ -32,7 +34,7 @@ pub async fn results(
     query: &str,
     page: u32,
     user_agent: &str,
-) -> Result<HashMap<String, RawSearchResult>, EngineErrorKind> {
+) -> Result<HashMap<String, RawSearchResult>, EngineError> {
     // Page number can be missing or empty string and so appropriate handling is required
     // so that upstream server recieves valid page number.
     let url: String = match page {
@@ -51,33 +53,71 @@ pub async fn results(
 
     // initializing HeaderMap and adding appropriate headers.
     let mut header_map = HeaderMap::new();
-    header_map.insert(USER_AGENT, user_agent.parse()?);
-    header_map.insert(REFERER, "https://google.com/".parse()?);
-    header_map.insert(CONTENT_TYPE, "application/x-www-form-urlencoded".parse()?);
-    header_map.insert(COOKIE, "kl=wt-wt".parse()?);
+    header_map.insert(
+        USER_AGENT,
+        user_agent
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
+    header_map.insert(
+        REFERER,
+        "https://google.com/"
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
+    header_map.insert(
+        CONTENT_TYPE,
+        "application/x-www-form-urlencoded"
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
+    header_map.insert(
+        COOKIE,
+        "kl=wt-wt"
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
 
     // fetch the html from upstream duckduckgo engine
     let results: String = reqwest::Client::new()
         .get(url)
-        .timeout(Duration::from_secs(30))
+        .timeout(Duration::from_secs(5))
         .headers(header_map) // add spoofed headers to emulate human behaviour
         .send()
-        .await?
+        .await
+        .into_report()
+        .change_context(EngineError::RequestError)?
         .text()
-        .await?;
+        .await
+        .into_report()
+        .change_context(EngineError::RequestError)?;
 
     let document: Html = Html::parse_document(&results);
 
-    let no_result: Selector = Selector::parse(".no-results")?;
+    let no_result: Selector = Selector::parse(".no-results")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".no-results"))?;
 
     if document.select(&no_result).next().is_some() {
-        return Err(EngineErrorKind::EmptyResultSet);
+        return Err(Report::new(EngineError::EmptyResultSet));
     }
 
-    let results: Selector = Selector::parse(".result")?;
-    let result_title: Selector = Selector::parse(".result__a")?;
-    let result_url: Selector = Selector::parse(".result__url")?;
-    let result_desc: Selector = Selector::parse(".result__snippet")?;
+    let results: Selector = Selector::parse(".result")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result"))?;
+    let result_title: Selector = Selector::parse(".result__a")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result__a"))?;
+    let result_url: Selector = Selector::parse(".result__url")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result__url"))?;
+    let result_desc: Selector = Selector::parse(".result__snippet")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result__snippet"))?;
 
     // scrape all the results from the html
     Ok(document

src/engines/engine_models.rs

@@ -1,8 +1,8 @@
 //! This module provides the error enum to handle different errors associated while requesting data from
 //! the upstream search engines with the search query provided by the user.
 
-use reqwest::header::InvalidHeaderValue;
-use scraper::error::SelectorErrorKind;
+use error_stack::Context;
+use std::fmt;
 
 /// A custom error type used for handle engine associated errors.
 ///
@@ -15,73 +15,24 @@ use scraper::error::SelectorErrorKind;
 /// and are errors mostly related to failure in initialization of HeaderMap, Selector errors and
 /// all other errors occuring within the code handling the `upstream search engines`.
 #[derive(Debug)]
-pub enum EngineErrorKind {
-    RequestError(reqwest::Error),
+pub enum EngineError {
     EmptyResultSet,
-    UnexpectedError {
-        message: String,
-        source: Option<Box<dyn std::error::Error>>,
-    },
+    RequestError,
+    UnexpectedError,
 }
 
-/// Implementing `Display` trait to make errors writable on the stdout and also providing/passing the
-/// appropriate errors that should be written to the stdout when this error is raised/encountered.
-impl std::fmt::Display for EngineErrorKind {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for EngineError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            EngineErrorKind::RequestError(request_error) => {
-                write!(f, "Request error: {}", request_error)
-            }
-            EngineErrorKind::EmptyResultSet => {
+            EngineError::EmptyResultSet => {
                 write!(f, "The upstream search engine returned an empty result set")
             }
-            EngineErrorKind::UnexpectedError { message, source } => {
-                write!(f, "Unexpected error: {}", message)?;
-                if let Some(source) = source {
-                    write!(f, "\nCaused by: {}", source)?;
-                }
-                Ok(())
+            EngineError::RequestError => {
+                write!(f, "Request error")
             }
+            EngineError::UnexpectedError => write!(f, "Unexpected error"),
         }
     }
 }
 
-/// Implementing `Error` trait to make the the `EngineErrorKind` enum an error type and
-/// mapping `ReqwestErrors` to `RequestError` and `UnexpectedError` errors to all other unexpected
-/// errors ocurring within the code handling the upstream search engines.
-impl std::error::Error for EngineErrorKind {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        match self {
-            EngineErrorKind::RequestError(request_error) => Some(request_error),
-            EngineErrorKind::UnexpectedError { source, .. } => source.as_deref().map(|s| s),
-            _ => None,
-        }
-    }
-}
-
-/// Implementing `From` trait to map the `SelectorErrorKind` to `UnexpectedError` variant.
-impl From<SelectorErrorKind<'_>> for EngineErrorKind {
-    fn from(err: SelectorErrorKind<'_>) -> Self {
-        Self::UnexpectedError {
-            message: err.to_string(),
-            source: None,
-        }
-    }
-}
-
-/// Implementing `From` trait to map the `InvalidHeaderValue` to `UnexpectedError` variant.
-impl From<InvalidHeaderValue> for EngineErrorKind {
-    fn from(err: InvalidHeaderValue) -> Self {
-        Self::UnexpectedError {
-            message: err.to_string(),
-            source: Some(Box::new(err)),
-        }
-    }
-}
-
-/// Implementing `From` trait to map all `reqwest::Error` to `UnexpectedError` variant.
-impl From<reqwest::Error> for EngineErrorKind {
-    fn from(err: reqwest::Error) -> Self {
-        Self::RequestError(err)
-    }
-}
+impl Context for EngineError {}

src/engines/searx.rs

@@ -8,7 +8,8 @@ use std::collections::HashMap;
 
 use crate::search_results_handler::aggregation_models::RawSearchResult;
 
-use super::engine_models::EngineErrorKind;
+use super::engine_models::EngineError;
+use error_stack::{IntoReport, Report, Result, ResultExt};
 
 /// This function scrapes results from the upstream engine duckduckgo and puts all the scraped
 /// results like title, visiting_url (href in html),engine (from which engine it was fetched from)
@@ -31,43 +32,76 @@ pub async fn results(
     query: &str,
     page: u32,
     user_agent: &str,
-) -> Result<HashMap<String, RawSearchResult>, EngineErrorKind> {
+) -> Result<HashMap<String, RawSearchResult>, EngineError> {
     // Page number can be missing or empty string and so appropriate handling is required
     // so that upstream server recieves valid page number.
     let url: String = format!("https://searx.work/search?q={query}&pageno={page}");
 
     // initializing headers and adding appropriate headers.
     let mut header_map = HeaderMap::new();
-    header_map.insert(USER_AGENT, user_agent.parse()?);
-    header_map.insert(REFERER, "https://google.com/".parse()?);
-    header_map.insert(CONTENT_TYPE, "application/x-www-form-urlencoded".parse()?);
-    header_map.insert(COOKIE, "categories=general; language=auto; locale=en; autocomplete=duckduckgo; image_proxy=1; method=POST; safesearch=2; theme=simple; results_on_new_tab=1; doi_resolver=oadoi.org; simple_style=auto; center_alignment=1; query_in_title=1; infinite_scroll=0; disabled_engines=; enabled_engines=\"archive is__general\\054yep__general\\054curlie__general\\054currency__general\\054ddg definitions__general\\054wikidata__general\\054duckduckgo__general\\054tineye__general\\054lingva__general\\054startpage__general\\054yahoo__general\\054wiby__general\\054marginalia__general\\054alexandria__general\\054wikibooks__general\\054wikiquote__general\\054wikisource__general\\054wikiversity__general\\054wikivoyage__general\\054dictzone__general\\054seznam__general\\054mojeek__general\\054naver__general\\054wikimini__general\\054brave__general\\054petalsearch__general\\054goo__general\"; disabled_plugins=; enabled_plugins=\"searx.plugins.hostname_replace\\054searx.plugins.oa_doi_rewrite\\054searx.plugins.vim_hotkeys\"; tokens=; maintab=on; enginetab=on".parse()?);
+    header_map.insert(
+        USER_AGENT,
+        user_agent
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
+    header_map.insert(
+        REFERER,
+        "https://google.com/"
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
+    header_map.insert(
+        CONTENT_TYPE,
+        "application/x-www-form-urlencoded"
+            .parse()
+            .into_report()
+            .change_context(EngineError::UnexpectedError)?,
+    );
+    header_map.insert(COOKIE, "categories=general; language=auto; locale=en; autocomplete=duckduckgo; image_proxy=1; method=POST; safesearch=2; theme=simple; results_on_new_tab=1; doi_resolver=oadoi.org; simple_style=auto; center_alignment=1; query_in_title=1; infinite_scroll=0; disabled_engines=; enabled_engines=\"archive is__general\\054yep__general\\054curlie__general\\054currency__general\\054ddg definitions__general\\054wikidata__general\\054duckduckgo__general\\054tineye__general\\054lingva__general\\054startpage__general\\054yahoo__general\\054wiby__general\\054marginalia__general\\054alexandria__general\\054wikibooks__general\\054wikiquote__general\\054wikisource__general\\054wikiversity__general\\054wikivoyage__general\\054dictzone__general\\054seznam__general\\054mojeek__general\\054naver__general\\054wikimini__general\\054brave__general\\054petalsearch__general\\054goo__general\"; disabled_plugins=; enabled_plugins=\"searx.plugins.hostname_replace\\054searx.plugins.oa_doi_rewrite\\054searx.plugins.vim_hotkeys\"; tokens=; maintab=on; enginetab=on".parse().into_report().change_context(EngineError::UnexpectedError)?);
 
     // fetch the html from upstream searx instance engine
     let results: String = reqwest::Client::new()
         .get(url)
         .headers(header_map) // add spoofed headers to emulate human behaviours.
         .send()
-        .await?
+        .await
+        .into_report()
+        .change_context(EngineError::RequestError)?
         .text()
-        .await?;
+        .await
+        .into_report()
+        .change_context(EngineError::RequestError)?;
 
     let document: Html = Html::parse_document(&results);
 
-    let no_result: Selector = Selector::parse("#urls>.dialog-error>p")?;
+    let no_result: Selector = Selector::parse("#urls>.dialog-error>p")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", "#urls>.dialog-error>p"))?;
 
     if let Some(no_result_msg) = document.select(&no_result).nth(1) {
         if no_result_msg.inner_html()
             == "we didn't find any results. Please use another query or search in more categories"
         {
-            return Err(EngineErrorKind::EmptyResultSet);
+            return Err(Report::new(EngineError::EmptyResultSet));
         }
     }
 
-    let results: Selector = Selector::parse(".result")?;
-    let result_title: Selector = Selector::parse("h3>a")?;
-    let result_url: Selector = Selector::parse("h3>a")?;
-    let result_desc: Selector = Selector::parse(".content")?;
+    let results: Selector = Selector::parse(".result")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".result"))?;
+    let result_title: Selector = Selector::parse("h3>a")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", "h3>a"))?;
+    let result_url: Selector = Selector::parse("h3>a")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", "h3>a"))?;
+
+    let result_desc: Selector = Selector::parse(".content")
+        .map_err(|_| Report::new(EngineError::UnexpectedError))
+        .attach_printable_lazy(|| format!("invalid CSS selector: {}", ".content"))?;
 
     // scrape all the results from the html
     Ok(document