fix: improve lint issues and add -D warnings to github ci

.github/workflows/main.yml

@@ -37,7 +37,7 @@ jobs:
         components: clippy
         override: true
     - name: Lint
-      run: cargo clippy --all-features
+      run: cargo clippy --all-features -- -D warnings
     - name: Build and run tests
       run: cargo test --all-features
 

src/error.rs

@@ -1,6 +1,6 @@
 // use std::backtrace::Backtrace;
 use std::error::Error as StdError;
-use std::fmt;
+use std::fmt::{self, Write};
 use std::io::Error as IOError;
 use std::num::ParseIntError;
 use std::string::FromUtf8Error;
@@ -205,7 +205,7 @@ fn template_segment(template_str: &str, line: usize, col: usize) -> String {
     let mut buf = String::new();
     for (line_count, line_content) in template_str.lines().enumerate() {
         if line_count >= line_start && line_count <= line_end {
-            buf.push_str(&format!("{:4} | {}\n", line_count, line_content));
+            let _ = writeln!(&mut buf, "{:4} | {}", line_count, line_content);
             if line_count == line - 1 {
                 buf.push_str("     |");
                 for c in 0..line_content.len() {

src/registry.rs

@@ -298,12 +298,9 @@ impl<'reg> Registry<'reg> {
     {
         let dir_path = dir_path.as_ref();
 
-        // Allowing dots at the beginning as to not break old applications.
-        let tpl_extension = if tpl_extension.starts_with(".") {
-            &tpl_extension[1..]
-        } else {
-            tpl_extension
-        };
+        // Allowing dots at the beginning as to not break old
+        // applications.
+        let tpl_extension = tpl_extension.strip_prefix('.').unwrap_or(tpl_extension);
 
         let walker = WalkDir::new(dir_path);
         let dir_iter = walker
@@ -322,7 +319,7 @@ impl<'reg> Registry<'reg> {
                 tpl_path
                     .file_stem()
                     .map(|stem| stem.to_string_lossy())
-                    .map(|stem| !(stem.starts_with(".") || stem.starts_with("#")))
+                    .map(|stem| !(stem.starts_with('.') || stem.starts_with('#')))
                     .unwrap_or(false)
             })
             .filter_map(|tpl_path| {

src/render.rs

@@ -779,7 +779,7 @@ fn indent_aware_write(
     out: &mut dyn Output,
 ) -> Result<(), RenderError> {
     if let Some(indent) = rc.get_indent_string() {
-        out.write(support::str::with_indent(v.as_ref(), indent).as_ref())?;
+        out.write(support::str::with_indent(v, indent).as_ref())?;
     } else {
         out.write(v.as_ref())?;
     }

src/support.rs

@@ -58,7 +58,7 @@ pub mod str {
     }
 
     /// add indent for lines but last
-    pub fn with_indent<'a>(s: &'a str, indent: &String) -> String {
+    pub fn with_indent(s: &str, indent: &str) -> String {
         let mut output = String::new();
 
         let mut it = s.chars().peekable();