From 82914d32d21d3f0cd98f02cb67fd97b84ce2631d Mon Sep 17 00:00:00 2001
From: "Jonathan B. Coe" <jonathanbcoe@gmail.com>
Date: Sat, 14 Mar 2026 15:47:03 +0000
Subject: [PATCH 1/2] Fast rebuilds of C/C++ code when needed.

Configures `CMake` to use `ccache` for faster C/C++ compilation.
Modifies `pyproject.toml` to enable `editable.rebuild` and specify
`build-dir` for `scikit-build-core`, ensuring fast, incremental
rebuilds when C/C++ sources or project metadata change.
---
 CMakeLists.txt | 11 +++++++++++
 pyproject.toml |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 48a45e4b8..061979a6d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,17 @@ endif()
 string(REGEX MATCH "^[0-9]+(\\.[0-9]+)*" CMAKE_NLE_VERSION "${NLE_VERSION}")
 project(nle VERSION ${CMAKE_NLE_VERSION})
 
+if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
+  find_program(CCACHE_FOUND ccache)
+  if(CCACHE_FOUND)
+    message(STATUS "ccache found, enabling for C and C++")
+    set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_FOUND}")
+    set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_FOUND}")
+  else()
+    message(STATUS "ccache not found, proceeding without it")
+  endif()
+endif()
+
 if(CMAKE_BUILD_TYPE MATCHES Debug)
   message("Debug build.")
   # Unclear if this is even necessary. `dsymutil rlmain -o rlmain.dSYM` seems to
diff --git a/pyproject.toml b/pyproject.toml
index d1ff3031e..f6d9640f3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -38,6 +38,8 @@ cmake.build-type = "Release"
 cmake.args = ["-DHACKDIR=nle/nethackdir", "-DPYTHON_PACKAGE_NAME=nle"]
 minimum-version = "build-system.requires"
 metadata.version.provider = "scikit_build_core.metadata.setuptools_scm"
+build-dir = "build/{wheel_tag}"
+editable.rebuild = true
 generate = [
   { path = "nle/version.py", template = '__version__ = "${version}"' },
 ]

From 842d289d3d2ad254a5e29e2ca0f7a37d99f96be0 Mon Sep 17 00:00:00 2001
From: "Jonathan B. Coe" <jonathanbcoe@gmail.com>
Date: Tue, 17 Mar 2026 21:46:46 +0000
Subject: [PATCH 2/2] Add clarifying comment for enabling ccache

---
 CMakeLists.txt | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 061979a6d..2036b9c7d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,12 +12,13 @@ endif()
 string(REGEX MATCH "^[0-9]+(\\.[0-9]+)*" CMAKE_NLE_VERSION "${NLE_VERSION}")
 project(nle VERSION ${CMAKE_NLE_VERSION})
 
+# Only enable ccache if this is the main project, not a sub-dependency.
 if(CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
-  find_program(CCACHE_FOUND ccache)
-  if(CCACHE_FOUND)
+  find_program(CCACHE_EXECUTABLE ccache)
+  if(CCACHE_EXECUTABLE)
     message(STATUS "ccache found, enabling for C and C++")
-    set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_FOUND}")
-    set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_FOUND}")
+    set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_EXECUTABLE}")
+    set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_EXECUTABLE}")
   else()
     message(STATUS "ccache not found, proceeding without it")
   endif()