[docs](trx-rs): generate the example config and correct the manual

trx-rs.toml.example was maintained by hand and had fallen well behind: no
[[rigs]], no [[remotes]], no [timeouts], no bandplan or decode-history
settings, and a [frontends.http].default_rig_id that had been renamed.

Generate it from the config structs instead, so a new field shows up the moment
it exists, and add a test that fails when the checked-in copy drifts:

    cargo run -p trx-config --example generate_example

Section comments come from a small table; a section without an entry is still
emitted, so forgetting a comment can never drop a setting from the example.

The manual was wrong about the basics.  It listed five config search paths, none
of which the loader has ever looked at (the real order is ./trx-rs.toml → XDG →
/etc), called --print-config output "fully commented" when it carries no
comments at all, and documented a TRX_PLUGIN_DIRS variable no code reads.  It
also still described [frontends.rigctl].port as the bind port years after
rig_ports replaced it.  Fixed, and the new configuration features are written
up alongside.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SyX26FCpMQxiBoC7r5K1A7
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-config/Cargo.toml

@@ -18,6 +18,7 @@ trx-core = { path = "../trx-core" }
 trx-decode-log = { path = "../decoders/trx-decode-log" }
 trx-reporting = { path = "../trx-reporting" }
 serde_ignored = "0.1"
+toml_edit = "0.22"
 
 [dev-dependencies]
 tempfile = "3"

src/trx-config/examples/generate_example.rs

@@ -0,0 +1,29 @@
+// SPDX-FileCopyrightText: 2026 Stan Grams <sjg@haxx.space>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Regenerate `trx-rs.toml.example` from the config structs.
+//!
+//! Run from anywhere in the workspace:
+//!
+//! ```text
+//! cargo run -p trx-config --example generate_example
+//! ```
+//!
+//! A test in `trx_config::example` fails when the checked-in file no longer
+//! matches, which is the reminder to run this.
+
+use std::path::PathBuf;
+
+fn main() -> std::io::Result<()> {
+    let target: PathBuf = std::env::args()
+        .nth(1)
+        .map(PathBuf::from)
+        .unwrap_or_else(|| {
+            PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../../trx-rs.toml.example")
+        });
+
+    std::fs::write(&target, trx_config::example::combined_example())?;
+    println!("Wrote {}", target.display());
+    Ok(())
+}

src/trx-config/src/client.rs

@@ -807,13 +807,10 @@ impl ClientConfig {
 
     /// Generate an example configuration wrapped under the `[trx-client]`
     /// section header, suitable for use in a combined `trx-rs.toml` file.
-    pub fn example_combined_toml() -> String {
-        #[derive(serde::Serialize)]
-        struct Wrapper {
-            #[serde(rename = "trx-client")]
-            inner: ClientConfig,
-        }
-        let example = ClientConfig {
+    /// The example configuration used by `--print-config` and by the
+    /// generated `trx-rs.toml.example`.
+    pub fn example_config() -> Self {
+        ClientConfig {
             general: GeneralConfig {
                 callsign: Some("N0CALL".to_string()),
                 website_url: Some("https://haxx.space".to_string()),
@@ -879,8 +876,21 @@ impl ClientConfig {
                 http_json: HttpJsonFrontendConfig::default(),
                 audio: AudioClientConfig::default(),
             },
-        };
-        toml::to_string_pretty(&Wrapper { inner: example }).unwrap_or_default()
+        }
+    }
+
+    /// Generate an example configuration wrapped under the `[trx-client]`
+    /// section header, suitable for use in a combined `trx-rs.toml` file.
+    pub fn example_combined_toml() -> String {
+        #[derive(serde::Serialize)]
+        struct Wrapper {
+            #[serde(rename = "trx-client")]
+            inner: ClientConfig,
+        }
+        toml::to_string_pretty(&Wrapper {
+            inner: ClientConfig::example_config(),
+        })
+        .unwrap_or_default()
     }
 }
 

src/trx-config/src/example.rs

@@ -0,0 +1,255 @@
+// SPDX-FileCopyrightText: 2026 Stan Grams <sjg@haxx.space>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Generating the example configuration from the config structs.
+//!
+//! `trx-rs.toml.example` used to be maintained by hand and had fallen years
+//! behind the code — no `[[rigs]]`, no `[[remotes]]`, no `[timeouts]`, no
+//! bandplan settings.  It is now produced from the structs themselves, so a new
+//! field appears in the example the moment it exists, and a test fails if the
+//! checked-in copy drifts.
+//!
+//! Section comments come from the table below.  A section without an entry is
+//! still emitted — only its explanatory text is missing — so forgetting to add
+//! one can never drop a setting from the example.
+
+use toml_edit::{DocumentMut, Item};
+
+use crate::{ClientConfig, ServerConfig};
+
+const HEADER: &str = "\
+# trx-rs example configuration
+#
+# Generated from the config structs; regenerate with:
+#     cargo run -p trx-config --example generate_example
+#
+# Both sections are optional: trx-server reads [trx-server], trx-client reads
+# [trx-client], and either may live in its own file with the section header
+# omitted.  Any string may use ${ENV_VAR}, and credentials may be moved out of
+# this file with the matching *_file keys.
+#
+# Check a config without starting anything:
+#     trx-server --check-config --config trx-rs.toml
+#     trx-client --check-config --config trx-rs.toml
+";
+
+/// Explanatory comments for config sections, keyed by dotted path.
+const SECTION_COMMENTS: &[(&str, &str)] = &[
+    ("trx-server", "Server: drives the radio hardware."),
+    (
+        "trx-server.general",
+        "Station identity.  Coordinates feed PSKReporter and the map.",
+    ),
+    (
+        "trx-server.rig",
+        "Single-rig layout.  For several radios, delete this and use [[rigs]].",
+    ),
+    (
+        "trx-server.rig.access",
+        "How to reach the radio: serial, tcp, or sdr.",
+    ),
+    ("trx-server.behavior", "CAT polling and retry behaviour."),
+    (
+        "trx-server.listen",
+        "JSON control listener that trx-client connects to.",
+    ),
+    (
+        "trx-server.listen.auth",
+        "Tokens clients must present.  Empty means no authentication.\n\
+         Use tokens_file = \"/etc/trx-rs/tokens\" to keep them out of this file.",
+    ),
+    ("trx-server.audio", "Opus audio stream for trx-client."),
+    (
+        "trx-server.decoders",
+        "Which decoders run.  Trimming this list saves real CPU on small boxes.\n\
+         Valid names: aprs, aprs_hf, ais, cw, ft2, ft4, ft8, lrpt, sstv, vdes, wefax, wspr.",
+    ),
+    (
+        "trx-server.pskreporter",
+        "Report FT8/FT4/WSPR spots to pskreporter.info.",
+    ),
+    ("trx-server.aprsfi", "Forward received APRS frames to APRS-IS."),
+    ("trx-server.decode_logs", "Write decodes to JSON Lines files."),
+    (
+        "trx-server.sdr",
+        "SoapySDR pipeline; used when [rig.access] type = \"sdr\".",
+    ),
+    ("trx-server.sdr.gain", "\"auto\" for hardware AGC, or \"manual\"."),
+    ("trx-server.sdr.squelch", "Software squelch on demodulated audio."),
+    (
+        "trx-server.sdr.noise_blanker",
+        "Impulse-noise suppression on the IQ stream.",
+    ),
+    (
+        "trx-server.timeouts",
+        "Timeout and buffer tuning.  The defaults suit most setups.",
+    ),
+    ("trx-client", "Client: exposes the radio to users."),
+    ("trx-client.general", "Labels shown in the web UI."),
+    (
+        "trx-client.remote",
+        "Legacy single-remote form; prefer [[remotes]] below.",
+    ),
+    (
+        "trx-client.frontends.http",
+        "Web UI.  default_rig_name and the per-rig maps are keyed by the\n\
+         [[remotes]] name, not the server-side rig id.",
+    ),
+    (
+        "trx-client.frontends.http.auth",
+        "Passphrase login for the web UI.  rx_passphrase_file and\n\
+         control_passphrase_file keep the secrets out of this file.",
+    ),
+    (
+        "trx-client.frontends.rigctl",
+        "Hamlib-compatible TCP interface, one listener per rig.",
+    ),
+    ("trx-client.frontends.http_json", "JSON-over-TCP control interface."),
+    ("trx-client.frontends.audio", "Where to fetch the audio stream from."),
+    (
+        "trx-client.frontends.audio.bridge",
+        "Play RX audio on a local sound device and capture TX from one.",
+    ),
+];
+
+/// Render the combined `trx-rs.toml.example` contents.
+pub fn combined_example() -> String {
+    let mut doc = DocumentMut::new();
+    doc.decor_mut().set_prefix(HEADER);
+
+    doc.insert("trx-server", section_item(&ServerConfig::example_config()));
+    doc.insert("trx-client", section_item(&ClientConfig::example_config()));
+
+    // Each section was serialized on its own, so both carry table positions
+    // starting at zero and would otherwise render interleaved.
+    renumber_tables(&mut doc);
+
+    for (path, comment) in SECTION_COMMENTS {
+        annotate(&mut doc, path, comment);
+    }
+
+    doc.to_string()
+}
+
+/// Renumber every table so the document renders in tree order.
+fn renumber_tables(doc: &mut DocumentMut) {
+    fn walk(item: &mut Item, next: &mut usize) {
+        match item {
+            Item::Table(table) => {
+                table.set_position(*next);
+                *next += 1;
+                for (_, child) in table.iter_mut() {
+                    walk(child, next);
+                }
+            }
+            Item::ArrayOfTables(array) => {
+                for table in array.iter_mut() {
+                    table.set_position(*next);
+                    *next += 1;
+                    for (_, child) in table.iter_mut() {
+                        walk(child, next);
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+
+    let mut next = 0;
+    for (_, item) in doc.as_table_mut().iter_mut() {
+        walk(item, &mut next);
+    }
+}
+
+/// Serialize one config into a toml_edit table.
+fn section_item<T: serde::Serialize>(config: &T) -> Item {
+    let rendered = toml::to_string_pretty(config).unwrap_or_default();
+    let doc: DocumentMut = rendered.parse().expect("serialized config must re-parse");
+    Item::Table(doc.as_table().clone())
+}
+
+/// Attach a comment above the table at `path`, if it exists.
+fn annotate(doc: &mut DocumentMut, path: &str, comment: &str) {
+    let mut item: Option<&mut Item> = None;
+    for segment in path.split('.') {
+        let next = match item {
+            None => doc.get_mut(segment),
+            Some(current) => current.as_table_mut().and_then(|t| t.get_mut(segment)),
+        };
+        match next {
+            Some(found) => item = Some(found),
+            None => return,
+        }
+    }
+
+    let Some(table) = item.and_then(|i| i.as_table_mut()) else {
+        return;
+    };
+    let body: String = comment
+        .lines()
+        .map(|line| format!("# {}\n", line.trim_start()))
+        .collect();
+    table.decor_mut().set_prefix(format!("\n{body}"));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::ConfigFile;
+
+    /// The checked-in example must match what the structs produce, so a new
+    /// config field cannot land without showing up in the example.
+    #[test]
+    fn test_checked_in_example_is_up_to_date() {
+        let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("../../trx-rs.toml.example")
+            .canonicalize()
+            .expect("example file must exist");
+        let on_disk = std::fs::read_to_string(&path).expect("example file must be readable");
+        assert_eq!(
+            on_disk,
+            combined_example(),
+            "trx-rs.toml.example is out of date; regenerate with \
+             `cargo run -p trx-config --example generate_example`"
+        );
+    }
+
+    #[test]
+    fn test_example_loads_and_validates() {
+        let mut file = tempfile::NamedTempFile::new().unwrap();
+        std::io::Write::write_all(&mut file, combined_example().as_bytes()).unwrap();
+
+        let server = ServerConfig::load_from_file(file.path()).expect("server section loads");
+        assert!(
+            server.unknown_keys.is_empty(),
+            "the generated example must not contain unknown keys: {:?}",
+            server.unknown_keys
+        );
+        server.config.validate().expect("server section validates");
+
+        let client = ClientConfig::load_from_file(file.path()).expect("client section loads");
+        assert!(
+            client.unknown_keys.is_empty(),
+            "the generated example must not contain unknown keys: {:?}",
+            client.unknown_keys
+        );
+        client.config.validate().expect("client section validates");
+    }
+
+    /// Every section that gained a comment must still exist under that path.
+    #[test]
+    fn test_section_comments_match_real_sections() {
+        let doc: DocumentMut = combined_example().parse().unwrap();
+        for (path, _) in SECTION_COMMENTS {
+            let mut item = None;
+            for segment in path.split('.') {
+                item = match item {
+                    None => doc.get(segment),
+                    Some(current) => current.as_table().and_then(|t| t.get(segment)),
+                };
+                assert!(item.is_some(), "commented section [{path}] no longer exists");
+            }
+        }
+    }
+}

src/trx-config/src/lib.rs

@@ -10,6 +10,7 @@
 //! it with, so the two can never drift apart.
 
 pub mod client;
+pub mod example;
 pub mod file;
 pub mod secrets;
 pub mod server;

src/trx-config/src/server.rs

@@ -727,13 +727,10 @@ impl ServerConfig {
 
     /// Generate an example configuration wrapped under the `[trx-server]`
     /// section header, suitable for use in a combined `trx-rs.toml` file.
-    pub fn example_combined_toml() -> String {
-        #[derive(serde::Serialize)]
-        struct Wrapper {
-            #[serde(rename = "trx-server")]
-            inner: ServerConfig,
-        }
-        let example = ServerConfig {
+    /// The example configuration used by `--print-config` and by the
+    /// generated `trx-rs.toml.example`.
+    pub fn example_config() -> Self {
+        ServerConfig {
             general: GeneralConfig {
                 callsign: Some("N0CALL".to_string()),
                 log_level: Some("info".to_string()),
@@ -763,8 +760,21 @@ impl ServerConfig {
             sdr: SdrConfig::default(),
             timeouts: TimeoutsConfig::default(),
             rigs: Vec::new(),
-        };
-        toml::to_string_pretty(&Wrapper { inner: example }).unwrap_or_default()
+        }
+    }
+
+    /// Generate an example configuration wrapped under the `[trx-server]`
+    /// section header, suitable for use in a combined `trx-rs.toml` file.
+    pub fn example_combined_toml() -> String {
+        #[derive(serde::Serialize)]
+        struct Wrapper {
+            #[serde(rename = "trx-server")]
+            inner: ServerConfig,
+        }
+        toml::to_string_pretty(&Wrapper {
+            inner: ServerConfig::example_config(),
+        })
+        .unwrap_or_default()
     }
 }