emit cargo metadata duiring build scripts to avoid outdated buildscript outputs (#6743)

* rebuild on revision change
* rerun grammar build if grammars change

helix-loader/build.rs

@@ -1,4 +1,5 @@
 use std::borrow::Cow;
+use std::path::Path;
 use std::process::Command;
 
 const VERSION: &str = include_str!("../VERSION");
@@ -11,7 +12,7 @@ fn main() {
         .filter(|output| output.status.success())
         .and_then(|x| String::from_utf8(x.stdout).ok());
 
-    let version: Cow<_> = match git_hash {
+    let version: Cow<_> = match &git_hash {
         Some(git_hash) => format!("{} ({})", VERSION, &git_hash[..8]).into(),
         None => VERSION.into(),
     };
@@ -23,4 +24,40 @@ fn main() {
 
     println!("cargo:rerun-if-changed=../VERSION");
     println!("cargo:rustc-env=VERSION_AND_GIT_HASH={}", version);
+
+    if git_hash.is_none() {
+        return;
+    }
+
+    // we need to revparse because the git dir could be anywhere if you are
+    // using detached worktrees but there is no good way to obtain an OsString
+    // from command output so for now we can't accept non-utf8 paths here
+    // probably rare enouch where it doesn't matter tough we could use gitoxide
+    // here but that would be make it a hard dependency and slow compile times
+    let Some(git_dir): Option<String> = Command::new("git")
+        .args(["rev-parse", "--git-dir"])
+        .output()
+        .ok()
+        .filter(|output| output.status.success())
+        .and_then(|x| String::from_utf8(x.stdout).ok())
+    else{ return; };
+    // If heads starts pointing at something else (different branch)
+    // we need to return
+    let head = Path::new(&git_dir).join("HEAD");
+    if head.exists() {
+        println!("cargo:rerun-if-changed={}", head.display());
+    }
+    // if the thing head points to (branch) itself changes
+    // we need to return
+    let Some(head_ref): Option<String> = Command::new("git")
+        .args(["symbolic-ref", "HEAD"])
+        .output()
+        .ok()
+        .filter(|output| output.status.success())
+        .and_then(|x| String::from_utf8(x.stdout).ok())
+    else{ return; };
+    let head_ref = Path::new(&git_dir).join(head_ref);
+    if head_ref.exists() {
+        println!("cargo:rerun-if-changed={}", head_ref.display());
+    }
 }

helix-loader/src/grammar.rs

@@ -413,6 +413,18 @@ fn build_tree_sitter_library(
     let mut library_path = parser_lib_path.join(&grammar.grammar_id);
     library_path.set_extension(DYLIB_EXTENSION);
 
+    // if we are running inside a buildscript emit cargo metadata
+    // to detect if we are running from a buildscript check some env variables
+    // that cargo only sets for build scripts
+    if std::env::var("OUT_DIR").is_ok() && std::env::var("CARGO").is_ok() {
+        if let Some(scanner_path) = scanner_path.as_ref().and_then(|path| path.to_str()) {
+            println!("cargo:rerun-if-changed={scanner_path}");
+        }
+        if let Some(parser_path) = parser_path.to_str() {
+            println!("cargo:rerun-if-changed={parser_path}");
+        }
+    }
+
     let recompile = needs_recompile(&library_path, &parser_path, &scanner_path)
         .context("Failed to compare source and binary timestamps")?;