From a5cf92664db9633b9fb1307a801d99de70d09aba Mon Sep 17 00:00:00 2001
From: Riteo <riteo@posteo.net>
Date: Wed, 13 Mar 2024 17:54:14 +0100
Subject: SCons: unify code generations routine and minimize timestamp changes

Previously, all of the code generation routines would just needlessly
write the same files over and over, even when not needed.

This became a problem with the advent of the experimental ninja backend
for SCons, which can be trivially enabled with a few lines of code and
relies on timestamp changes, making it thus impractical.
---
 methods.py | 60 ++++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 34 insertions(+), 26 deletions(-)

(limited to 'methods.py')

diff --git a/methods.py b/methods.py
index 5aa34888eb..6cd944c6b0 100644
--- a/methods.py
+++ b/methods.py
@@ -228,14 +228,22 @@ def get_version_info(module_version_string="", silent=False):
     return version_info
 
 
+def write_file_if_needed(path, string):
+    try:
+        with open(path, "r", encoding="utf-8", newline="\n") as f:
+            if f.read() == string:
+                return
+    except FileNotFoundError:
+        pass
+
+    with open(path, "w", encoding="utf-8", newline="\n") as f:
+        f.write(string)
+
+
 def generate_version_header(module_version_string=""):
     version_info = get_version_info(module_version_string)
 
-    # NOTE: It is safe to generate these files here, since this is still executed serially.
-
-    with open("core/version_generated.gen.h", "w", encoding="utf-8", newline="\n") as f:
-        f.write(
-            """\
+    version_info_header = """\
 /* THIS FILE IS GENERATED DO NOT EDIT */
 #ifndef VERSION_GENERATED_GEN_H
 #define VERSION_GENERATED_GEN_H
@@ -252,21 +260,20 @@ def generate_version_header(module_version_string=""):
 #define VERSION_DOCS_URL "https://docs.godotengine.org/en/" VERSION_DOCS_BRANCH
 #endif // VERSION_GENERATED_GEN_H
 """.format(
-                **version_info
-            )
-        )
+        **version_info
+    )
 
-    with open("core/version_hash.gen.cpp", "w", encoding="utf-8", newline="\n") as fhash:
-        fhash.write(
-            """\
+    version_hash_data = """\
 /* THIS FILE IS GENERATED DO NOT EDIT */
 #include "core/version.h"
 const char *const VERSION_HASH = "{git_hash}";
 const uint64_t VERSION_TIMESTAMP = {git_timestamp};
 """.format(
-                **version_info
-            )
-        )
+        **version_info
+    )
+
+    write_file_if_needed("core/version_generated.gen.h", version_info_header)
+    write_file_if_needed("core/version_hash.gen.cpp", version_hash_data)
 
 
 def parse_cg_file(fname, uniforms, sizes, conditionals):
@@ -385,15 +392,18 @@ def is_module(path):
 
 
 def write_disabled_classes(class_list):
-    with open("core/disabled_classes.gen.h", "w", encoding="utf-8", newline="\n") as f:
-        f.write("/* THIS FILE IS GENERATED DO NOT EDIT */\n")
-        f.write("#ifndef DISABLED_CLASSES_GEN_H\n")
-        f.write("#define DISABLED_CLASSES_GEN_H\n\n")
-        for c in class_list:
-            cs = c.strip()
-            if cs != "":
-                f.write("#define ClassDB_Disable_" + cs + " 1\n")
-        f.write("\n#endif\n")
+    file_contents = ""
+
+    file_contents += "/* THIS FILE IS GENERATED DO NOT EDIT */\n"
+    file_contents += "#ifndef DISABLED_CLASSES_GEN_H\n"
+    file_contents += "#define DISABLED_CLASSES_GEN_H\n\n"
+    for c in class_list:
+        cs = c.strip()
+        if cs != "":
+            file_contents += "#define ClassDB_Disable_" + cs + " 1\n"
+    file_contents += "\n#endif\n"
+
+    write_file_if_needed("core/disabled_classes.gen.h", file_contents)
 
 
 def write_modules(modules):
@@ -435,9 +445,7 @@ void uninitialize_modules(ModuleInitializationLevel p_level) {
         uninitialize_cpp,
     )
 
-    # NOTE: It is safe to generate this file here, since this is still executed serially
-    with open("modules/register_module_types.gen.cpp", "w", encoding="utf-8", newline="\n") as f:
-        f.write(modules_cpp)
+    write_file_if_needed("modules/register_module_types.gen.cpp", modules_cpp)
 
 
 def convert_custom_modules_path(path):
-- 
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