ci: extend doc-linter to MyST Markdown

Active docs are now MyST `.md`; the linter previously only inspected
`.rst` and `.txt`, so ~250 active pages were unchecked for IP usage and
line length on every PR.

scripts/doc-linter.py:
- Add `.md` to the extension filter (use `endswith` for correctness;
  the prior 4-char slice silently skipped `.md` files).
- Track MyST/Markdown fenced code blocks (```` ``` ```` and `:::`) for
  line-length exemption — same semantics as `.. code-block::` for RST.
- Recognize both suppression marker forms: `.. stop_vyoslinter` /
  `.. start_vyoslinter` (RST and `.txt` includes) and `% stop_vyoslinter`
  / `% start_vyoslinter` (MyST). Both work in either context; pick the
  form that matches the surrounding parser.
- Replace the brittle `try/finally: fp.close()` with a `with` block —
  the previous form raised `UnboundLocalError` if `open()` itself
  failed.
- Fix typo `forgett` → `forget`.

.github/instructions/rst-linter.instructions.md → doc-linter.instructions.md:
- Broaden `applyTo` from `**/*.rst` to `**/*.md,**/*.rst,**/*.txt`.
- Document MyST suppression syntax and fenced-code line-length
  exemption.
- Note the parser-form rule for `{eval-rst}` blocks.

No regression on `.txt` includes: identical lint output verified
against the origin/rolling baseline on a sample of files.

Pre-existing IP violations exist in 14 `.md` files (e.g.
`configexamples/lac-lns.md` line 95 — a `8.8.8.8` already wrapped in
`% stop_vyoslinter`/`% start_vyoslinter`, correctly suppressed). PRs
touching unsuppressed violations will start failing CI; this is the
intent of enabling the check.

🤖 Generated by [robots](https://vyos.io)

1 files changed, 73 insertions, 60 deletions

diff --git a/scripts/doc-linter.py b/scripts/doc-linter.py
index 3dc7c2fc..ec00472c 100644
--- a/scripts/doc-linter.py
+++ b/scripts/doc-linter.py
@@ -27,6 +27,20 @@ MAC = r'([0-9A-F]{2}[:-]){5}([0-9A-F]{2})'
 
 NUMBER = r"([\s']\d+[\s'])"
 
+SUPPORTED_EXTS = ('.md', '.rst', '.txt')
+
+# MyST / Markdown fenced code block: leading whitespace + 3+ backticks or 3+ colons.
+# Same character and length-or-greater closes.
+MD_FENCE_RE = re.compile(r'^(\s*)(`{3,}|:{3,})')
+
+
+def is_suppression_marker(line, kind):
+    """Detect `.. stop_vyoslinter` (RST/txt) or `% stop_vyoslinter` (MyST)."""
+    token = f"{kind}_vyoslinter"
+    if token not in line:
+        return False
+    return f".. {token}" in line or f"% {token}" in line
+
 
 def lint_mac(cnt, line):
     mac = re.search(MAC, line, re.I)
@@ -79,65 +93,64 @@ def lint_linelen(cnt, line):
 
 def handle_file_action(filepath):
     errors = []
-    try:
-        with open(filepath) as fp:
-            line = fp.readline()
-            cnt = 1
-            test_line_lenght = True
-            start_vyoslinter = True
-            indentation = 0
-            while line:
-                # search for ignore linter comments in lines
-                if ".. stop_vyoslinter" in line:
-                    start_vyoslinter = False
-                if ".. start_vyoslinter" in line:
-                    start_vyoslinter = True
-                if start_vyoslinter:
-                    # ignore every '.. code-block::' for line lenght
-                    # rst code-block have its own style in html the format in rst
-                    # and the build page must be the same
-                    if test_line_lenght is False:
-                        if len(line) > indentation:
-                            #print(f"'{line}'")
-                            #print(indentation)
-                            if line[indentation].isspace() is False:
-                                test_line_lenght = True
-
-                    if ".. code-block::" in line:
-                        test_line_lenght = False
-                        indentation = 0
-                        for i in line:
-                            if i.isspace():
-                                indentation = indentation + 1
-                            else:
-                                break
-                    
-                    err_mac = lint_mac(cnt, line.strip())
-                    # disable mac detection for the moment, too many false positives
-                    err_mac = None
-                    err_ip4 = lint_ipv4(cnt, line.strip())
-                    err_ip6 = lint_ipv6(cnt, line.strip())
-                    if test_line_lenght:
-                        err_len = lint_linelen(cnt, line)
+    in_md_fence = False
+    md_fence_char = None
+    md_fence_min_len = 0
+    in_rst_codeblock = False
+    rst_codeblock_indent = 0
+    start_vyoslinter = True
+    cnt = 0
+
+    with open(filepath) as fp:
+        for cnt, line in enumerate(fp, start=1):
+            if is_suppression_marker(line, 'stop'):
+                start_vyoslinter = False
+            if is_suppression_marker(line, 'start'):
+                start_vyoslinter = True
+
+            if not start_vyoslinter:
+                continue
+
+            # MD/MyST fenced code block tracking (``` or :::)
+            fence_match = MD_FENCE_RE.match(line)
+            if fence_match:
+                fence = fence_match.group(2)
+                fence_char = fence[0]
+                fence_len = len(fence)
+                if not in_md_fence:
+                    in_md_fence = True
+                    md_fence_char = fence_char
+                    md_fence_min_len = fence_len
+                elif fence_char == md_fence_char and fence_len >= md_fence_min_len:
+                    in_md_fence = False
+
+            # RST `.. code-block::` tracking (existing semantics for .rst/.txt).
+            if in_rst_codeblock:
+                if len(line) > rst_codeblock_indent and not line[rst_codeblock_indent].isspace():
+                    in_rst_codeblock = False
+            if not in_rst_codeblock and ".. code-block::" in line:
+                in_rst_codeblock = True
+                rst_codeblock_indent = 0
+                for ch in line:
+                    if ch.isspace():
+                        rst_codeblock_indent += 1
                     else:
-                        err_len = None
-                    if err_mac:
-                        errors.append(err_mac)
-                    if err_ip4:
-                        errors.append(err_ip4)
-                    if err_ip6:
-                        errors.append(err_ip6)
-                    if err_len:
-                        errors.append(err_len)
-                
-                line = fp.readline()
-                cnt += 1
-            
-            # ensure linter was not stop on top and forgot to tun on again
-            if start_vyoslinter == False:
-                errors.append((f"Don't forgett to turn linter back on", cnt, 'error'))
-    finally:
-        fp.close()
+                        break
+
+            test_line_length = not (in_md_fence or in_rst_codeblock)
+
+            err_mac = lint_mac(cnt, line.strip())
+            # disable mac detection for the moment, too many false positives
+            err_mac = None
+            err_ip4 = lint_ipv4(cnt, line.strip())
+            err_ip6 = lint_ipv6(cnt, line.strip())
+            err_len = lint_linelen(cnt, line) if test_line_length else None
+            for e in (err_mac, err_ip4, err_ip6, err_len):
+                if e:
+                    errors.append(e)
+
+        if not start_vyoslinter:
+            errors.append(("Don't forget to turn linter back on", cnt, 'error'))
 
     if len(errors) > 0:
         '''
@@ -156,14 +169,14 @@ def main():
     try:
         files = ast.literal_eval(sys.argv[1])
         for file in files:
-                if file[-4:] in [".rst", ".txt"] and "_build" not in file:
+                if file.endswith(SUPPORTED_EXTS) and "_build" not in file:
                     if handle_file_action(file) is False:
                         bool_error = False
     except Exception as e:
         for root, dirs, files in os.walk("docs"):
             path = root.split(os.sep)
             for file in files:
-                if file[-4:] in [".rst", ".txt"] and "_build" not in path:
+                if file.endswith(SUPPORTED_EXTS) and "_build" not in path:
                     fpath = '/'.join(path)
                     filepath = f"{fpath}/{file}"
                     if handle_file_action(filepath) is False: