From bb92a538b4282e065b2de323f17100dde78877cf Mon Sep 17 00:00:00 2001
From: tomoaki <whiteunyora@gmail.com>
Date: Sun, 28 Dec 2025 13:57:05 +0900
Subject: [PATCH] runner: resolve repo root without NYASH_ROOT

---
 src/runner/modes/common_util/resolve/mod.rs   |  1 +
 src/runner/modes/common_util/resolve/root.rs  | 54 +++++++++++++++++++
 .../common_util/resolve/strip/prelude.rs      |  8 +--
 3 files changed, 59 insertions(+), 4 deletions(-)
 create mode 100644 src/runner/modes/common_util/resolve/root.rs

diff --git a/src/runner/modes/common_util/resolve/mod.rs b/src/runner/modes/common_util/resolve/mod.rs
index 2e909aed..c8042cdb 100644
--- a/src/runner/modes/common_util/resolve/mod.rs
+++ b/src/runner/modes/common_util/resolve/mod.rs
@@ -21,6 +21,7 @@
 
 pub mod context;
 pub mod path_util;
+pub mod root;
 pub mod prelude_manager;
 pub mod seam;
 pub mod selfhost_pipeline;
diff --git a/src/runner/modes/common_util/resolve/root.rs b/src/runner/modes/common_util/resolve/root.rs
new file mode 100644
index 00000000..1078727c
--- /dev/null
+++ b/src/runner/modes/common_util/resolve/root.rs
@@ -0,0 +1,54 @@
+//! root — repository root resolution helpers (SSOT)
+//!
+//! `NYASH_ROOT` is allowed as an override for tools, but runtime semantics must
+//! not depend on whether it is set. When we need to locate repo-relative assets
+//! (e.g., operator preludes), prefer resolving a stable root via:
+//! 1) `NYASH_ROOT` when set
+//! 2) walking up from an on-disk hint file (e.g., the main source file)
+//! 3) current working directory
+//! 4) current executable path
+
+use std::path::{Path, PathBuf};
+
+pub fn resolve_repo_root(hint_file: Option<&str>) -> Option<PathBuf> {
+    if let Ok(root) = std::env::var("NYASH_ROOT") {
+        let p = PathBuf::from(root);
+        if p.exists() {
+            return Some(p);
+        }
+    }
+
+    if let Some(hint) = hint_file {
+        if let Some(root) = walk_up_to_repo_root(Path::new(hint).parent()?) {
+            return Some(root);
+        }
+    }
+
+    if let Ok(cwd) = std::env::current_dir() {
+        if let Some(root) = walk_up_to_repo_root(&cwd) {
+            return Some(root);
+        }
+    }
+
+    if let Ok(exe) = std::env::current_exe() {
+        if let Some(dir) = exe.parent() {
+            if let Some(root) = walk_up_to_repo_root(dir) {
+                return Some(root);
+            }
+        }
+    }
+
+    None
+}
+
+fn walk_up_to_repo_root(start: &Path) -> Option<PathBuf> {
+    let mut cur = start;
+    for _ in 0..16 {
+        if cur.join("Cargo.toml").exists() {
+            return Some(cur.to_path_buf());
+        }
+        cur = cur.parent()?;
+    }
+    None
+}
+
diff --git a/src/runner/modes/common_util/resolve/strip/prelude.rs b/src/runner/modes/common_util/resolve/strip/prelude.rs
index 70b5df98..25b89c58 100644
--- a/src/runner/modes/common_util/resolve/strip/prelude.rs
+++ b/src/runner/modes/common_util/resolve/strip/prelude.rs
@@ -31,14 +31,14 @@ pub fn resolve_prelude_paths_profiled(
     let opbox_all = crate::config::env::env_bool("NYASH_OPERATOR_BOX_ALL")
         || crate::config::env::env_bool("NYASH_BUILDER_OPERATOR_BOX_ALL_CALL");
 
-    if let Ok(root) = std::env::var("NYASH_ROOT") {
+    if let Some(root) = crate::runner::modes::common_util::resolve::root::resolve_repo_root(Some(filename)) {
         let must_have = [
             "apps/lib/std/operators/stringify.hako",
             "apps/lib/std/operators/compare.hako",
             "apps/lib/std/operators/add.hako",
         ];
         for rel in must_have.iter() {
-            let p = std::path::Path::new(&root).join(rel);
+            let p = root.join(rel);
             if p.exists() {
                 let path = p.to_string_lossy().to_string();
                 if !out.iter().any(|x| x == &path) {
@@ -49,7 +49,7 @@ pub fn resolve_prelude_paths_profiled(
     }
     // Inject remaining arithmetic/bitwise/unary operator modules when ALL is requested
     if opbox_all {
-        if let Ok(root) = std::env::var("NYASH_ROOT") {
+        if let Some(root) = crate::runner::modes::common_util::resolve::root::resolve_repo_root(Some(filename)) {
             let rels = vec![
                 "apps/lib/std/operators/sub.hako",
                 "apps/lib/std/operators/mul.hako",
@@ -66,7 +66,7 @@ pub fn resolve_prelude_paths_profiled(
                 "apps/lib/std/operators/bitnot.hako",
             ];
             for rel in rels {
-                let p = std::path::Path::new(&root).join(rel);
+                let p = root.join(rel);
                 if p.exists() {
                     let path = p.to_string_lossy().to_string();
                     if !out.iter().any(|x| x == &path) {