From a3df139b7bdfe6f572f1596bd631abe697ed6d83 Mon Sep 17 00:00:00 2001
From: rami3l <rami3l@outlook.com>
Date: Mon, 21 Aug 2023 11:22:22 +0800
Subject: [PATCH] Refactor `components_missing_msg` and add a `Panics` section
 to its docstring

---
 src/dist/dist.rs | 70 +++++++++++++++++++++++++++---------------------
 1 file changed, 40 insertions(+), 30 deletions(-)

diff --git a/src/dist/dist.rs b/src/dist/dist.rs
index 97093a21c1b..9390fa942de 100644
--- a/src/dist/dist.rs
+++ b/src/dist/dist.rs
@@ -42,46 +42,56 @@ static TOOLCHAIN_CHANNELS: &[&str] = &[
     r"\d{1}\.\d{1,3}(?:\.\d{1,2})?",
 ];
 
+/// Returns a error message indicating that certain [`Component`]s are missing in a toolchain distribution.
+/// This message is currently used exclusively in toolchain-wide operations,
+/// otherwise [`component_unavailable_msg`](`crate::errors::component_unavailable_msg`) will be used.
+///
+/// # Panics
+/// This function will panic when the collection of unavailable components `cs` is empty.
 fn components_missing_msg(cs: &[Component], manifest: &ManifestV2, toolchain: &str) -> String {
-    assert!(!cs.is_empty());
     let mut buf = vec![];
     let suggestion = format!("    rustup toolchain add {toolchain} --profile minimal");
     let nightly_tips = "Sometimes not all components are available in any given nightly. ";
 
-    if cs.len() == 1 {
-        let _ = writeln!(
-            buf,
-            "component {} is unavailable for download for channel '{}'",
-            &cs[0].description(manifest),
-            toolchain,
-        );
+    match cs {
+        [] => panic!("`components_missing_msg` should not be called with an empty collection of unavailable components"),
+        [c] => {
+            _ = writeln!(
+                buf,
+                "component {} is unavailable for download for channel '{}'",
+                c.description(manifest),
+                toolchain,
+            );
+
+            if toolchain.starts_with("nightly") {
+                _ = write!(buf, "{nightly_tips}");
+            }
 
-        if toolchain.starts_with("nightly") {
-            let _ = write!(buf, "{nightly_tips}");
+            _ = write!(
+                buf,
+                "If you don't need the component, you could try a minimal installation with:\n\n{suggestion}"
+            );
         }
+        cs => {
+            let cs_str = cs
+                .iter()
+                .map(|c| c.description(manifest))
+                .collect::<Vec<_>>()
+                .join(", ");
+            _ = write!(
+                buf,
+                "some components unavailable for download for channel '{toolchain}': {cs_str}"
+            );
 
-        let _ = write!(
-            buf,
-            "If you don't need the component, you could try a minimal installation with:\n\n{suggestion}"
-        );
-    } else {
-        let cs_str = cs
-            .iter()
-            .map(|c| c.description(manifest))
-            .collect::<Vec<_>>()
-            .join(", ");
-        let _ = write!(
-            buf,
-            "some components unavailable for download for channel '{toolchain}': {cs_str}"
-        );
+            if toolchain.starts_with("nightly") {
+                let _ = write!(buf, "{nightly_tips}");
+            }
 
-        if toolchain.starts_with("nightly") {
-            let _ = write!(buf, "{nightly_tips}");
+            _ = write!(
+                buf,
+                "If you don't need the components, you could try a minimal installation with:\n\n{suggestion}"
+            );
         }
-        let _ = write!(
-            buf,
-            "If you don't need the components, you could try a minimal installation with:\n\n{suggestion}"
-        );
     }
 
     String::from_utf8(buf).unwrap()