make git optional to support offline and packaged builds

README.md

@@ -29,11 +29,6 @@ UDP, TCP, file connection protocols with a rich set of features.
 | [`mavlink-core`](https://crates.io/crates/mavlink-core) | Core protocol types, parser/serializer, and connection traits |
 | [`mavlink-bindgen`](https://crates.io/crates/mavlink-bindgen) | XML-to-Rust code generator used by `mavlink` |
 
-## Build requirements
-
-Building the `mavlink` crate runs a build script that initializes
-the bundled MAVLink definition submodule, so `git` must be available.
-
 ## Quick start
 
 Add the crate:

mavlink/build/main.rs

@@ -1,5 +1,6 @@
 #![recursion_limit = "256"]
 
+use std::collections::{BTreeMap, BTreeSet};
 use std::env;
 use std::fs::read_dir;
 use std::path::Path;
@@ -9,29 +10,29 @@ use mavlink_bindgen::XmlDefinitions;
 
 fn main() -> ExitCode {
     let src_dir = Path::new(env!("CARGO_MANIFEST_DIR"));
+    let mavlink_dir = src_dir.join("mavlink");
 
-    // Check if git is installed
-    if Command::new("git").arg("--version").status().is_err() {
-        eprintln!("error: Git is not installed or could not be found.");
-        return ExitCode::FAILURE;
-    }
-
-    // Update and init submodule
-    if let Err(error) = Command::new("git")
-        .arg("submodule")
-        .arg("update")
-        .arg("--init")
-        .current_dir(src_dir)
-        .status()
-    {
-        eprintln!("Failed to update MAVLink definitions submodule: {error}");
-        return ExitCode::FAILURE;
+    // It is a submodule if it contains `.git` or if it's completely empty (uninitialized)
+    let is_mavlink_empty = read_dir(&mavlink_dir)
+        .map(|mut d| d.next().is_none())
+        .unwrap_or(true);
+    let is_submodule = mavlink_dir.join(".git").exists() || is_mavlink_empty;
+
+    if is_submodule {
+        if let Err(error) = Command::new("git")
+            .arg("submodule")
+            .arg("update")
+            .arg("--init")
+            .current_dir(src_dir)
+            .status()
+        {
+            eprintln!("Failed to update MAVLink definitions submodule: {error}");
+            return ExitCode::FAILURE;
+        }
     }
 
     // find & apply patches to XML definitions to avoid crashes
     let patch_dir = src_dir.join("build/patches");
-    let mavlink_dir = src_dir.join("mavlink");
-
     if let Ok(dir) = read_dir(patch_dir) {
         for entry in dir.flatten() {
             if let Err(error) = Command::new("git")
@@ -46,40 +47,65 @@ fn main() -> ExitCode {
         }
     }
 
-    let out_dir = env::var("OUT_DIR").unwrap();
+    let source_definitions_dir = mavlink_dir.join("message_definitions/v1.0");
 
-    let source_definitions_dir = src_dir.join("mavlink/message_definitions/v1.0");
+    // Check if the source definitions directory exists
+    if !source_definitions_dir.is_dir() {
+        eprintln!(
+            "MAVLink message definitions directory not found at: {}\n\
+             Ensure submodules are included.",
+            source_definitions_dir.display(),
+        );
+        return ExitCode::FAILURE;
+    }
 
-    let enabled_dialects: Vec<String> = env::vars()
+    let enabled_dialects: BTreeSet<String> = env::vars()
         .filter_map(|(key, _)| {
             key.strip_prefix("CARGO_FEATURE_DIALECT_")
                 .map(str::to_lowercase)
         })
         .collect();
 
-    let mut definitions_to_bind = vec![];
+    let mut definitions_to_bind = BTreeSet::new();
+
+    if !enabled_dialects.is_empty() {
+        // Handle case-insensitive Cargo features against case-sensitive files e.g., `csAirLink.xml`.
+        let mut available_dialects = BTreeMap::new();
+        for entry in read_dir(&source_definitions_dir)
+            .into_iter()
+            .flatten()
+            .flatten()
+        {
+            let path = entry.path();
+            let Some(stem) = path.file_stem() else {
+                continue;
+            };
+
+            available_dialects.insert(stem.to_string_lossy().to_lowercase(), path);
+        }
 
-    if let Ok(dir) = read_dir(&source_definitions_dir) {
-        for entry in dir.flatten() {
-            let filename = entry
-                .path()
-                .file_stem()
-                .unwrap()
-                .to_string_lossy()
-                .to_lowercase();
-
-            if enabled_dialects.contains(&filename) {
-                definitions_to_bind.push(entry.path());
-            }
+        // Check if the expected dialects requested by Cargo features are missing
+        for dialect in &enabled_dialects {
+            let Some(actual_path) = available_dialects.get(dialect) else {
+                eprintln!(
+                    "Dialect definition for '{}' not found in {}",
+                    dialect,
+                    source_definitions_dir.display(),
+                );
+                return ExitCode::FAILURE;
+            };
+
+            definitions_to_bind.insert(actual_path.clone());
         }
     }
 
     let xml_definitions = if definitions_to_bind.is_empty() {
         XmlDefinitions::Directory(source_definitions_dir)
     } else {
-        XmlDefinitions::Files(definitions_to_bind)
+        XmlDefinitions::Files(definitions_to_bind.into_iter().collect())
     };
 
+    let out_dir = env::var("OUT_DIR").unwrap();
     let result = match mavlink_bindgen::generate(xml_definitions, out_dir) {
         Ok(r) => r,
         Err(e) => {