1 files changed, 29 insertions, 5 deletions

diff --git a/src/config/mod.rs b/src/config/mod.rs
index 99690ae..0c57713 100644
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -260,8 +260,12 @@ pub(crate) const OPTIONS: &[OptionSpec] = &[
         "transports",
         Kind::List,
         "NAME,[NAME...]",
-        Some("mycelium"),
-        "The transports this node uses, in order of preference: mycelium, libp2p and tor (in builds with the libp2p and tor features). A peer is reached on the first one both have, until the paths are measured (then on the fastest); nodes on several carry the traffic between nodes that share none.",
+        if cfg!(feature = "mycelium") {
+            Some("mycelium")
+        } else {
+            None
+        },
+        "The transports this node uses, in order of preference: mycelium, libp2p and tor (each in builds with its cargo feature; mycelium is the default where built). A peer is reached on the first one both have, until the paths are measured (then on the fastest); nodes on several carry the traffic between nodes that share none.",
     ),
     option(
         "libp2p-listen",
@@ -501,12 +505,18 @@ pub(crate) struct Settings {
     pub(crate) tor_port: u16,
     #[serde(default)]
     pub(crate) relay_only: bool,
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) mycelium_rest_url: Option<String>,
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) mycelium_key_file: Option<PathBuf>,
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) mycelium_network_key_file: Option<PathBuf>,
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) mycelium_network_name: Option<String>,
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) mycelium_tcp_listen_port: Option<u16>,
     #[serde(default = "default_mycelium_peers")]
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) mycelium_peers: Vec<String>,
     pub(crate) debug_epoch: Option<u64>,
 }
@@ -532,12 +542,17 @@ fn default_electorate_window() -> Duration {
 fn default_blob_chunk() -> u64 {
     64 * 1024
 }
+/// Mycelium where built; else none, so the transports must be named.
 fn default_transports() -> Vec<String> {
-    vec!["mycelium".to_owned()]
+    if cfg!(feature = "mycelium") {
+        vec!["mycelium".to_owned()]
+    } else {
+        Vec::new()
+    }
 }
 /// The transports `transports` may name, and whether this build has each.
 pub(crate) const TRANSPORTS: &[(&str, bool)] = &[
-    ("mycelium", true),
+    ("mycelium", cfg!(feature = "mycelium")),
     ("libp2p", cfg!(feature = "libp2p")),
     ("tor", cfg!(feature = "tor")),
 ];
@@ -553,6 +568,7 @@ fn default_mycelium_peers() -> Vec<String> {
 
 impl Settings {
     /// `mycelium-rest-url`, parsed (checked when loading).
+    #[cfg_attr(not(feature = "mycelium"), allow(dead_code))]
     pub(crate) fn mycelium_rest_url(&self) -> Option<url::Url> {
         self.mycelium_rest_url
             .as_deref()
@@ -628,7 +644,15 @@ impl Settings {
             }
         }
         if self.transports.is_empty() {
-            bail!("transports: a node needs at least one");
+            bail!(
+                "transports: a node needs at least one (this build has: {})",
+                TRANSPORTS
+                    .iter()
+                    .filter(|(_, built)| *built)
+                    .map(|(name, _)| *name)
+                    .collect::<Vec<_>>()
+                    .join(", ")
+            );
         }
         if self.transports.iter().any(|name| name == "tor") && self.tor_state_dir.is_none() {
             bail!(