Modify build.py to make the patch-application process resistant to CRLF nonsense

build.py

@@ -7,8 +7,6 @@
 # script are in README.md
 #
 
-#
-
 
 import sys, os, json, shutil, subprocess, re, time, tarfile
 import itertools, hashlib, zipfile, fnmatch
@@ -88,6 +86,40 @@ def expand_json_file(sourcefile, outputfile, config):
     expanded = expand_json(data, vars(config))
     Path(outputfile).write_text(json.dumps(expanded, indent=4))
 
+#
+# Applying patches to files with DOS line endings.
+#
+# We want to apply a patch to the UnrealEngine source, and some but not all
+# of the files we want to patch have DOS line endings.  Unfortunately, the
+# unix patch utility can't handle a codebase with mixed line endings.
+# To make it work, we convert all files to UNIX line endings, apply the
+# patch, and then convert the appropriate files back.
+#
+
+def patched_files(patchfn):
+    patch_lines = Path(patchfn).read_text().splitlines()
+    return [line[6:].strip() for line in patch_lines if line.startswith('--- a/')]
+
+def dos2unix(fn):
+    before = Path(fn).read_text()
+    after = before.replace("\r\n", "\n")
+    if before != after:
+        Path(fn).write_text(after)
+        return True
+    return False
+
+def unix2dos(fn):
+    before = Path(fn).read_text()
+    after = before.replace("\n", "\r\n")
+    if before != after:
+        Path(fn).write_text(after)
+        return True
+    return False
+
+#
+# Given a patch file, generate a list of the files being modified.
+#
+
 #
 # Determining the build configuration.
 #
@@ -159,7 +191,6 @@ def unzip_unreal_engine_and_apply_patch():
     """
     Unzip the unreal engine source, then apply a patch.
     """
-    # Find out the unreal version that we're using
     if not Path(UNREALENGINE).is_dir():
         zipfn = f"{INTEGRATION}/UnrealEngine.zip";
         with zipfile.ZipFile(zipfn, 'r') as z:
@@ -170,9 +201,14 @@ def unzip_unreal_engine_and_apply_patch():
         shutil.rmtree(UNREALENGINE, ignore_errors=True)
         shutil.rmtree(unrealversion, ignore_errors=True)
         shell(INTEGRATION, "unzip UnrealEngine.zip")
+        patchfile = f"{INTEGRATION}/EnginePatches/EnginePatch"
+        dos2unix(patchfile)
+        rel_files = patched_files(patchfile)
+        abs_files = [ os.path.join(unrealversion, file) for file in rel_files ]
+        dos_files = [ file for file in abs_files if dos2unix(file)]
+        shell(unrealversion, f"patch -p1 < {patchfile}")
+        for file in dos_files: unix2dos(file)
         Path(unrealversion).rename(UNREALENGINE)
-        shell(UNREALENGINE, f"patch -p1 < {INTEGRATION}/EnginePatches/EnginePatch")
-
 
 def generate_buildconfiguration_xml():
     """