Warn on console= karg if --console could have been used instead

If one or more console= kargs are specified to the install or iso/pxe
customize subcommands, and Console can successfully parse all of those
kargs, warn the user that they might benefit from specifying them using
the console mechanism instead.

For legibility, wrap the message at 80 characters, but avoid wrapping in
the middle of the example argument lists.  Use the textwrap crate to do
this.  textwrap is already a clap dependency without default features, and
we also avoid non-default features here, so this doesn't increase the
binary weight.

Cargo.toml

@@ -77,6 +77,7 @@ serde_json = "^1.0"
 serde_with = ">= 1.9.4, < 2"
 serde_yaml = ">= 0.8, < 0.10"
 tempfile = ">= 3.1, < 4"
+textwrap = { version = ">= 0.15.0, < 0.16.0", default-features = false }
 thiserror = "1.0"
 url = ">= 2.1, < 3.0"
 uuid = { version = ">= 0.8, < 2.0", features = ["v4"] }

docs/release-notes.md

@@ -20,6 +20,7 @@ Minor changes:
 - Fix unlikely decompression error reading initrd
 - Add release notes to documentation
 - iso: Detect incomplete ISO files
+- Warn if console kargs could have used `--console`/`--dest-console` instead
 
 Internal changes:
 
@@ -30,7 +31,8 @@ Internal changes:
 Packaging changes:
 
 - Require Rust ≥ 1.58.0
-- Add dependency on `zstd` crate and `libzstd` shared library
+- Add dependencies on `textwrap` and `zstd` crates
+- Add dependency on `libzstd` shared library
 - Support `serde_yaml` 0.9
 - Remove non-Linux dependencies from vendor archive
 - Install example installer config file in `/usr/share/coreos-installer`

src/cmdline/console.rs

@@ -94,6 +94,55 @@ impl Console {
     pub fn karg(&self) -> String {
         format!("{KARG_PREFIX}{}", self)
     }
+
+    /// Write a warning message to stdout if kargs contains "console="
+    /// arguments we can parse and no "console=" arguments we can't.  The
+    /// warning suggests that users use console_option instead of
+    /// karg_option to specify the desired console.
+    pub fn maybe_warn_on_kargs(kargs: &[String], karg_option: &str, console_option: &str) {
+        use textwrap::{fill, Options, WordSplitter};
+        if let Some(args) = Self::maybe_console_args_from_kargs(kargs) {
+            // automatically wrap the message, but use Unicode non-breaking
+            // spaces to avoid wrapping in the middle of the argument
+            // strings, and then replace the non-breaking spaces afterward
+            const NBSP: &str = "\u{a0}";
+            let msg = format!(
+                "Note: consider using \"{}\" instead of \"{}\" to configure both kernel and bootloader consoles.",
+                args.iter()
+                    .map(|a| format!("{console_option}{NBSP}{a}"))
+                    .collect::<Vec<String>>()
+                    .join(NBSP),
+                args.iter()
+                    .map(|a| format!("{karg_option}{NBSP}console={a}"))
+                    .collect::<Vec<String>>()
+                    .join(NBSP),
+            );
+            let wrapped = fill(
+                &msg,
+                Options::new(80)
+                    .break_words(false)
+                    .word_splitter(WordSplitter::NoHyphenation),
+            )
+            .replace(NBSP, " ");
+            eprintln!("\n{}\n", wrapped);
+        }
+    }
+
+    /// If kargs contains at least one console argument and all console
+    /// arguments are parseable as consoles, return a vector of verbatim
+    /// (unparsed) console arguments with the console= prefixes removed.
+    fn maybe_console_args_from_kargs(kargs: &[String]) -> Option<Vec<&str>> {
+        let (parseable, unparseable): (Vec<&str>, Vec<&str>) = kargs
+            .iter()
+            .filter(|a| a.starts_with(KARG_PREFIX))
+            .map(|a| &a[KARG_PREFIX.len()..])
+            .partition(|a| Console::from_str(a).is_ok());
+        if !parseable.is_empty() && unparseable.is_empty() {
+            Some(parseable)
+        } else {
+            None
+        }
+    }
 }
 
 impl FromStr for Console {
@@ -257,4 +306,42 @@ mod tests {
             Console::from_str(input).unwrap_err();
         }
     }
+
+    #[test]
+    fn maybe_console_args_from_kargs() {
+        assert_eq!(
+            Console::maybe_console_args_from_kargs(&[
+                "foo".into(),
+                "console=ttyS0".into(),
+                "bar".into()
+            ]),
+            Some(vec!["ttyS0"])
+        );
+        assert_eq!(
+            Console::maybe_console_args_from_kargs(&[
+                "foo".into(),
+                "console=ttyS0".into(),
+                "console=tty0".into(),
+                "console=tty0".into(),
+                "console=ttyAMA1,115200n8".into(),
+                "bar".into()
+            ]),
+            Some(vec!["ttyS0", "tty0", "tty0", "ttyAMA1,115200n8"])
+        );
+        assert_eq!(
+            Console::maybe_console_args_from_kargs(&[
+                "foo".into(),
+                "console=ttyS0".into(),
+                "console=ttyS1z".into(),
+                "console=tty0".into(),
+                "bar".into()
+            ]),
+            None
+        );
+        assert_eq!(
+            Console::maybe_console_args_from_kargs(&["foo".into(), "bar".into()]),
+            None
+        );
+        assert_eq!(Console::maybe_console_args_from_kargs(&[]), None);
+    }
 }

src/install.rs

@@ -421,6 +421,7 @@ fn write_disk(
         if !config.append_karg.is_empty() || !config.delete_karg.is_empty() {
             eprintln!("Modifying kernel arguments");
 
+            Console::maybe_warn_on_kargs(&config.append_karg, "--append-karg", "--console");
             visit_bls_entry_options(mount.mountpoint(), |orig_options: &str| {
                 KargsEditor::new()
                     .append(config.append_karg.as_slice())

src/live/customize.rs

@@ -108,6 +108,11 @@ impl LiveInitrd {
         for arg in &common.dest_console {
             conf.dest_console(arg)?;
         }
+        Console::maybe_warn_on_kargs(
+            &common.dest_karg_append,
+            "--dest-karg-append",
+            "--dest-console",
+        );
         for arg in &common.dest_karg_append {
             conf.dest_karg_append(arg);
         }