Support wasm target

Cargo.toml

@@ -13,12 +13,14 @@ exclude = [".github/"]
 
 [dependencies]
 crc32fast = "^1"
-hostname = "^0.3"
 md5 = "^0.7"
 once_cell = "^1"
 rand = "^0.8"
 thiserror = "^1"
 
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+hostname = "^0.3"
+
 [target.'cfg(target_os = "macos")'.dependencies]
 sysctl = "^0.4"
 

src/machine_id.rs

@@ -6,9 +6,7 @@ use sysctl::{Sysctl, SysctlError};
 pub fn get() -> [u8; 3] {
     let id = match machine_id().unwrap_or_default() {
         x if !x.is_empty() => x,
-        _ => hostname::get()
-            .map(|s| s.into_string().unwrap_or_default())
-            .unwrap_or_default(),
+        _ => hostname_fallback(),
     };
 
     let mut bytes = [0_u8; 3];
@@ -21,6 +19,19 @@ pub fn get() -> [u8; 3] {
     bytes
 }
 
+#[cfg(not(target_arch = "wasm32"))]
+fn hostname_fallback() -> String {
+    hostname::get()
+        .map(|s| s.into_string().unwrap_or_default())
+        .unwrap_or_default()
+}
+
+// `hostname` crate doesn't support wasm, so use an empty string to generate random bytes.
+#[cfg(target_arch = "wasm32")]
+fn hostname_fallback() -> String {
+    "".to_owned()
+}
+
 // https://github.com/rs/xid/blob/efa678f304ab65d6d57eedcb086798381ae22206/hostid_linux.go
 // Not checking "/sys/class/dmi/id/product_uuid" because normal users can't read it.
 #[cfg(target_os = "linux")]