fix clippy lints and improve error handling

src/main.rs

@@ -348,6 +348,15 @@ fn output_html(
     }
 
     std::fs::create_dir_all("output")?;
+    {
+        let temp_path = "output/calendars.html.tmp";
+        let final_path = "output/calendars.html";
+        let mut f = std::fs::File::create(temp_path)?;
+
+        f.write_all("".as_bytes())?;
+        std::fs::rename(temp_path, final_path)?;
+    }
+
     {
         let temp_path = "output/index.html.tmp";
         let final_path = "output/index.html";

src/wac_campfire.rs

@@ -110,7 +110,8 @@ impl Calendar {
     }
 
     pub(crate) fn read_from_config(config: Config) -> Result<Self> {
-        let s = std::fs::read_to_string(&config.dl.file_path)?;
+        let path = &config.dl.file_path;
+        let s = std::fs::read_to_string(path).with_context(|| format!("Couldn't read {path:?}"))?;
         Self::read_from_str(config, &s)
     }
 }

src/wac_common_ninja.rs

@@ -94,7 +94,8 @@ impl Calendar {
     }
 
     pub(crate) fn read_from_config(config: Config) -> Result<Self> {
-        let s = std::fs::read_to_string(&config.dl.file_path)?;
+        let path = &config.dl.file_path;
+        let s = std::fs::read_to_string(path).with_context(|| format!("Couldn't read {path:?}"))?;
         Self::read_from_str(config, &s)
     }
 }

src/wac_ical.rs

@@ -150,7 +150,7 @@ fn ical_event_instances(
         vec![dtstart_normalized]
     };
 
-    let instances = dates
+    dates
         .into_iter()
         .map(|dtstart| {
             let has_rrule = ev.properties().get("RRULE").is_some();
@@ -179,8 +179,7 @@ fn ical_event_instances(
                 url,
             })
         })
-        .collect();
-    instances
+        .collect()
 }
 
 /// Used to link recurrence exceptions to the original events they replace
@@ -268,7 +267,8 @@ impl Calendar {
     }
 
     pub(crate) fn read_from_config(config: Config) -> Result<Self> {
-        let s = std::fs::read_to_string(&config.dl.file_path)?;
+        let path = &config.dl.file_path;
+        let s = std::fs::read_to_string(path).with_context(|| format!("Couldn't read {path:?}"))?;
         Self::read_from_str(config, &s)
     }
 }