source_group: Support forward slashes in group hierarchy

Fixes: #18076

Help/command/source_group.rst

@@ -37,11 +37,13 @@ explicitly lists the file with ``FILES`` will be favored, if any.
 If no group explicitly lists the file, the *last* group whose
 regular expression matches the file will be favored.
 
-The ``<name>`` of the group and ``<prefix>`` argument may contain backslashes
-to specify subgroups:
+The ``<name>`` of the group and ``<prefix>`` argument may contain forward
+slashes or backslashes to specify subgroups.  Backslashes need to be escaped
+appropriately:
 
 .. code-block:: cmake
 
+  source_group(base/subdir ...)
   source_group(outer\\inner ...)
   source_group(TREE <root> PREFIX sources\\inc ...)
 

Help/release/dev/source_group_forward_slashes.rst

@@ -0,0 +1,5 @@
+source_group_forward_slashes
+----------------------------
+
+* The :command:`source_group` command now also recognizes forward slashes
+  as subgroup delimiters, not just backslashes.

Source/cmMakefile.cxx

@@ -2404,11 +2404,11 @@ cmSourceGroup* cmMakefile::GetOrCreateSourceGroup(
 
 cmSourceGroup* cmMakefile::GetOrCreateSourceGroup(const std::string& name)
 {
-  const char* delimiter = this->GetDefinition("SOURCE_GROUP_DELIMITER");
-  if (delimiter == nullptr) {
-    delimiter = "\\";
+  const char* delimiters = this->GetDefinition("SOURCE_GROUP_DELIMITER");
+  if (delimiters == nullptr) {
+    delimiters = "/\\";
   }
-  return this->GetOrCreateSourceGroup(cmTokenize(name, delimiter));
+  return this->GetOrCreateSourceGroup(cmTokenize(name, delimiters));
 }
 
 /**

Tests/SourceGroups/CMakeLists.txt

@@ -30,6 +30,9 @@ source_group(Base\\Sub1\\Base FILES bar.c)
 # a group without files, is currently not created
 source_group(EmptyGroup)
 
+# Forward slashes can be delimiters too
+source_group(Base/Nested FILES nested.c)
+
 set(root ${CMAKE_CURRENT_SOURCE_DIR})
 
 set(tree_files_without_prefix ${root}/sub1/tree_bar.c
@@ -58,4 +61,5 @@ source_group(PREFIX "" FILES ${tree_files_with_empty_prefix} TREE ${root})
 
 add_executable(SourceGroups main.c bar.c foo.c sub1/foo.c sub1/foobar.c baz.c
                             ${tree_files_with_prefix} ${tree_files_without_prefix}
-                            ${tree_files_with_empty_prefix} README.txt)
+                            ${tree_files_with_empty_prefix} README.txt
+                            nested.c)

Tests/SourceGroups/main.c

@@ -12,6 +12,7 @@ extern int tree_empty_prefix_bar(void);
 extern int tree_bar(void);
 extern int tree_foobar(void);
 extern int tree_baz(void);
+extern int nested(void);
 
 int main()
 {
@@ -23,5 +24,8 @@ int main()
          "tree_empty_prefix_bar: %d\n",
          tree_prefix_foo(), tree_prefix_bar(), tree_bar(), tree_foobar(),
          tree_baz(), tree_empty_prefix_foo(), tree_empty_prefix_bar());
+
+  printf("nested: %d\n", nested());
+
   return 0;
 }

Tests/SourceGroups/nested.c

@@ -0,0 +1,4 @@
+int nested(void)
+{
+  return 123;
+}