new: flag rust-toolchain.toml pins in pkh new

src/new/questions.rs

@@ -160,6 +160,22 @@ async fn run_wizard(mut cli: NewCli) -> Result<NewOptions, Box<dyn Error>> {
     }
     let template = TemplateId::parse(cli.lang.as_deref().unwrap_or_default())?;
 
+    // The rust toolchain pin of the packaged project does not travel into
+    // the chroot build: surface it now so a too-old pin is not a surprise
+    // when `pkh deb` compiles with the distribution's rustc.
+    let toolchain_pin = if template == TemplateId::Rust {
+        probe.as_ref().and_then(|p| p.toolchain_pin.clone())
+    } else {
+        None
+    };
+    if let Some(pin) = &toolchain_pin {
+        log::info!(
+            "Project pins rust {pin} via rust-toolchain.toml; the chroot \
+             build uses the distribution's rustc and ignores the pin — \
+             adjust or remove it if the code needs newer compiler features"
+        );
+    }
+
     // 3. Source location. Skipped (with the inline notice) when a confident
     //    detection already decided to package the current directory; a
     //    --source flag skips it too.
@@ -398,7 +414,7 @@ async fn run_wizard(mut cli: NewCli) -> Result<NewOptions, Box<dyn Error>> {
 
     // Summary screen + final confirmation: Ctrl+C or 'n' abort with
     // nothing written (generation is all-or-nothing later anyway).
-    println!("{}", summary_text(&opts));
+    println!("{}", summary_text(&opts, toolchain_pin.as_deref()));
     if !prompt::confirm("Generate?", true)? {
         return Err("Aborted: nothing was written to disk.".into());
     }
@@ -714,12 +730,13 @@ pub fn watch_template(homepage: Option<&str>) -> Option<String> {
     ))
 }
 
-/// The summary screen shown before the final `Generate?` confirmation
-/// (spec transcript): identity line, template/license/maintainer line, the
-/// generated-file overview and — for a metapackage — the Depends payload,
-/// for a skeleton — the upstream files that will be created, and for rust —
-/// a warning when dependencies cannot be vendored on this host.
-pub fn summary_text(opts: &NewOptions) -> String {
+/// The pre-flight summary screen shown before the final `Generate?`
+/// confirmation (spec transcript): identity line, template/license/maintainer
+/// line, the generated-file overview and — for a metapackage — the Depends
+/// payload, for a skeleton — the upstream files that will be created, and
+/// for rust — the probed toolchain pin (when any; the chroot build ignores
+/// it) plus a warning when dependencies cannot be vendored on this host.
+pub fn summary_text(opts: &NewOptions, toolchain_pin: Option<&str>) -> String {
     let template = templates::get(opts.template);
     let mut lines = Vec::new();
 
@@ -756,6 +773,13 @@ pub fn summary_text(opts: &NewOptions) -> String {
                 "  debian/rules      cargo build --release --offline (vendored at generation)"
                     .to_string(),
             );
+            // A pinned rust-toolchain.toml does not reach the chroot build:
+            // flagged here so a too-old pin is no surprise later.
+            if let Some(pin) = toolchain_pin {
+                lines.push(format!(
+                    "  rust-toolchain    {pin} (ignored by the chroot build)"
+                ));
+            }
         } else {
             lines.push(format!("  debian/rules      {}", template.rules_dh_line()));
         }
@@ -923,7 +947,7 @@ mod tests {
 
     #[test]
     fn summary_screen_skeleton() {
-        let text = summary_text(&opts(Tid::Makefile));
+        let text = summary_text(&opts(Tid::Makefile), None);
         assert!(
             text.contains("mytool 0.1.0-1 · builds for ubuntu/resolute"),
             "{text}"
@@ -956,7 +980,7 @@ mod tests {
         let mut o = opts(Tid::Empty);
         o.depends = vec!["hello".to_string(), "hello-data (>= 1.0)".to_string()];
         o.source_dir = options::SourceDir::Here;
-        let text = summary_text(&o);
+        let text = summary_text(&o, None);
         assert!(text.contains("Architecture: all"), "{text}");
         assert!(
             text.contains("Depends           hello, hello-data (>= 1.0)"),
@@ -973,7 +997,7 @@ mod tests {
         o.release = true;
         o.autopkgtest = true;
         o.watch = Some("version=4\n".to_string());
-        let text = summary_text(&o);
+        let text = summary_text(&o, None);
         assert!(text.contains("0.1.0-1 resolute, Initial release"), "{text}");
         assert!(
             text.contains("debian/tests      autopkgtest smoke test"),
@@ -987,7 +1011,7 @@ mod tests {
     /// yet (regression: it claimed "(vendored)" before generating).
     #[test]
     fn summary_screen_rust_does_not_presume_vendoring() {
-        let text = summary_text(&opts(Tid::Rust));
+        let text = summary_text(&opts(Tid::Rust), None);
         assert!(
             text.contains("cargo build --release --offline (vendored at generation)"),
             "{text}"
@@ -995,6 +1019,23 @@ mod tests {
         assert!(!text.contains("(vendored)"), "{text}");
     }
 
+    /// A probed rust toolchain pin surfaces in the summary as its own row
+    /// (rust template only), flagged as ignored by the chroot build.
+    #[test]
+    fn summary_screen_shows_the_toolchain_pin() {
+        let text = summary_text(&opts(Tid::Rust), Some("1.98.0"));
+        assert!(
+            text.contains("rust-toolchain    1.98.0 (ignored by the chroot build)"),
+            "{text}"
+        );
+
+        // No pin, no row.
+        assert!(!summary_text(&opts(Tid::Rust), None).contains("rust-toolchain"));
+        // A pin under a template other than rust is not shown either (the
+        // pin only matters for a cargo build).
+        assert!(!summary_text(&opts(Tid::Go), Some("1.98.0")).contains("rust-toolchain"));
+    }
+
     #[test]
     fn answer_validators() {
         assert!(validate_revision_answer("1").is_ok());