scripts: compliance: add a compliance check to keep blocks of code sorted

This allows defining a list within two marker (zephyr-keep-sorted-start
and zephyr-keep-sorted-stop), and have the CI validate that the block is
kept sorted every time stuff gets added to it.

This is mainly for Kconfig and CMake include lists so that there's no
ambiguity on where to add new stuff.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>

.gitignore

@@ -76,6 +76,7 @@ ImageSize.txt
 Kconfig.txt
 KconfigBasic.txt
 KconfigBasicNoModules.txt
+KeepSorted.txt
 MaintainersFormat.txt
 ModulesMaintainers.txt
 Nits.txt

scripts/ci/check_compliance.py

@@ -1163,6 +1163,59 @@ class YAMLLint(ComplianceTest):
                                       p.line, col=p.column, desc=p.desc)
 
 
+class KeepSorted(ComplianceTest):
+    """
+    Check for blocks of code or config that should be kept sorted.
+    """
+    name = "KeepSorted"
+    doc = "Check for blocks of code or config that should be kept sorted."
+    path_hint = "<git-top>"
+
+    MARKER = "zephyr-keep-sorted"
+
+    def check_file(self, file, fp):
+        lines = []
+        in_block = False
+
+        start_marker = f"{self.MARKER}-start"
+        stop_marker = f"{self.MARKER}-stop"
+
+        for line_num, line in enumerate(fp.readlines(), start=1):
+            if start_marker in line:
+                if in_block:
+                    desc = f"nested {start_marker}"
+                    self.fmtd_failure("error", "KeepSorted", file, line_num,
+                                     desc=desc)
+                in_block = True
+                lines = []
+            elif stop_marker in line:
+                if not in_block:
+                    desc = f"{stop_marker} without {start_marker}"
+                    self.fmtd_failure("error", "KeepSorted", file, line_num,
+                                     desc=desc)
+                in_block = False
+
+                if lines != sorted(lines):
+                    desc = f"sorted block is not sorted"
+                    self.fmtd_failure("error", "KeepSorted", file, line_num,
+                                     desc=desc)
+            elif not line.strip() or line.startswith("#"):
+                # Ignore comments and blank lines
+                continue
+            elif in_block:
+                if line.startswith((" ", "\t")):
+                    lines[-1] += line
+                else:
+                    lines.append(line)
+
+        if in_block:
+            self.failure(f"unterminated {start_marker} in {file}")
+
+    def run(self):
+        for file in get_files(filter="d"):
+            with open(file, "r") as fp:
+                self.check_file(file, fp)
+
 def init_logs(cli_arg):
     # Initializes logging