Add MDS041 rule to flag raw HTML in Markdown documents (#199)

* Implement MDS041 no-inline-html rule

Adds a new opt-in rule (MDS041) that flags raw HTML in Markdown —
both block-level HTMLBlock nodes and inline RawHTML nodes — with
configurable `allow` (tag allowlist) and `allow-comments` settings.
PI directives, autolinks, code blocks, and closing tags are
unconditionally skipped. Includes unit tests, integration fixtures,
rule README, and registration in main + integration test runner.

https://claude.ai/code/session_01MmZvugtRBav5yYwZ4gzZYS

* Fix coverage gaps in noinlinehtml rule

Remove unreachable defensive guards in htmlBlockBytes, blockLine, and
inlineLine (goldmark always produces non-empty Lines for HTMLBlock and
non-empty Segments for RawHTML). Add TestMetadata to cover Category().
Rule package is now at 100% statement coverage.

https://claude.ai/code/session_01MmZvugtRBav5yYwZ4gzZYS

* Address Copilot review: accurate column, fix comment message

- Compute line and column from the raw byte offset (via lineColOfOffset)
  so inline HTML mid-line reports the correct column instead of always 1.
- Fix comment diagnostic message from confusing "inline HTML <<!--> is
  not allowed" to "inline HTML <!-- is not allowed" by passing the
  display string pre-formatted instead of wrapping all tags in <>.
- Update unit tests to assert correct column numbers.
- Update bad fixtures to match the new column and message values.

https://claude.ai/code/session_01MmZvugtRBav5yYwZ4gzZYS

* Fix HTMLBlock column for indented block HTML

CommonMark allows up to 3 spaces of indentation before block HTML.
Use bytes.IndexByte to find the '<' within the line segment so the
reported column points at the tag rather than the start of the line.
Add TestCheck_IndentedBlockHTML_CorrectColumn to cover this path.

https://claude.ai/code/session_01MmZvugtRBav5yYwZ4gzZYS

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: jeduden

PLAN.md

@@ -21,7 +21,7 @@ footer: |
 | 102 | 🔲     | opus   | [Builder interface and mdsmith build subcommand](plan/102_build-subcommand.md)                       |
 | 103 | 🔲     | opus   | [Build target staleness and dependency tracking](plan/103_build-staleness-and-deps.md)               |
 | 104 | 🔲     | sonnet | [Build lifecycle hooks (before/after)](plan/104_build-lifecycle-hooks.md)                            |
-| 105 | 🔲     | sonnet | [No inline HTML rule](plan/105_no-inline-html.md)                                                    |
+| 105 | ✅     | sonnet | [No inline HTML rule](plan/105_no-inline-html.md)                                                    |
 | 106 | 🔲     | sonnet | [Emphasis style rule](plan/106_emphasis-style.md)                                                    |
 | 107 | 🔲     | opus   | [No reference-style links rule](plan/107_no-reference-style.md)                                      |
 | 108 | 🔲     | sonnet | [Horizontal rule style rule](plan/108_horizontal-rule-style.md)                                      |

cmd/mdsmith/main.go

@@ -49,6 +49,7 @@ import (
 	_ "github.com/jeduden/mdsmith/internal/rules/noemphasisasheading"
 	_ "github.com/jeduden/mdsmith/internal/rules/noemptyalttext"
 	_ "github.com/jeduden/mdsmith/internal/rules/nohardtabs"
+	_ "github.com/jeduden/mdsmith/internal/rules/noinlinehtml"
 	_ "github.com/jeduden/mdsmith/internal/rules/nomultipleblanks"
 	_ "github.com/jeduden/mdsmith/internal/rules/notrailingpunctuation"
 	_ "github.com/jeduden/mdsmith/internal/rules/notrailingspaces"

internal/integration/rules_test.go

@@ -41,6 +41,7 @@ import (
 	_ "github.com/jeduden/mdsmith/internal/rules/noemphasisasheading"
 	_ "github.com/jeduden/mdsmith/internal/rules/noemptyalttext"
 	_ "github.com/jeduden/mdsmith/internal/rules/nohardtabs"
+	_ "github.com/jeduden/mdsmith/internal/rules/noinlinehtml"
 	_ "github.com/jeduden/mdsmith/internal/rules/nomultipleblanks"
 	_ "github.com/jeduden/mdsmith/internal/rules/notrailingpunctuation"
 	_ "github.com/jeduden/mdsmith/internal/rules/notrailingspaces"

internal/rules/MDS041-no-inline-html/README.md

@@ -0,0 +1,100 @@
+---
+id: MDS041
+name: no-inline-html
+status: ready
+description: >-
+  Raw HTML tags in Markdown are not allowed; use a
+  Markdown construct or an mdsmith directive instead.
+---
+# MDS041: no-inline-html
+
+Raw HTML tags in Markdown are not allowed; use a
+Markdown construct or an mdsmith directive instead.
+
+## Config
+
+Enable with default settings (empty allowlist,
+comments permitted):
+
+```yaml
+rules:
+  no-inline-html: true
+```
+
+Enable with specific tags allowed:
+
+```yaml
+rules:
+  no-inline-html:
+    allow: [kbd, sub, sup]
+    allow-comments: true
+```
+
+Disable:
+
+```yaml
+rules:
+  no-inline-html: false
+```
+
+### Settings
+
+| Setting          | Type            | Default | Description                                            |
+|------------------|-----------------|---------|--------------------------------------------------------|
+| `allow`          | list of strings | `[]`    | Tag names that are permitted (replaces, not appended). |
+| `allow-comments` | bool            | `true`  | Whether HTML comments (`<!-- ... -->`) are allowed.    |
+
+## Examples
+
+### Bad
+
+<?include
+file: bad/inline-span.md
+wrap: markdown
+?>
+
+```markdown
+# Title
+
+text <span>x</span> text
+```
+
+<?/include?>
+
+### Good
+
+<?include
+file: good/allowed-tag.md
+wrap: markdown
+?>
+
+```markdown
+# Title
+
+Press <kbd>Enter</kbd> to continue.
+```
+
+<?/include?>
+
+## What is not flagged
+
+- Fenced and indented code blocks containing HTML
+- Inline code spans
+- Autolinks (`<https://example.com>`)
+- mdsmith directives (`<?name ... ?>`) — block forms
+  are parsed as `ProcessingInstruction` nodes; inline
+  forms are skipped because they start with `<?`
+- HTML entities in text (`&amp;`, `&#x2014;`)
+- Closing tags (`</div>`) — the matching opening tag
+  already produced a diagnostic
+
+## Meta-Information
+
+- **ID**: MDS041
+- **Name**: `no-inline-html`
+- **Status**: ready
+- **Default**: disabled (opt-in)
+- **Fixable**: no
+- **Implementation**:
+  [source](./)
+- **Category**: meta

internal/rules/MDS041-no-inline-html/bad/block-div.md

@@ -0,0 +1,11 @@
+---
+settings:
+  allow-comments: true
+diagnostics:
+  - line: 3
+    column: 1
+    message: "inline HTML <div> is not allowed"
+---
+# Title
+
+<div>block content</div>

internal/rules/MDS041-no-inline-html/bad/comment-disallowed.md

@@ -0,0 +1,11 @@
+---
+settings:
+  allow-comments: false
+diagnostics:
+  - line: 3
+    column: 1
+    message: "inline HTML <!-- is not allowed"
+---
+# Title
+
+<!-- this comment is not allowed -->

internal/rules/MDS041-no-inline-html/bad/inline-span.md

@@ -0,0 +1,11 @@
+---
+settings:
+  allow-comments: true
+diagnostics:
+  - line: 3
+    column: 6
+    message: "inline HTML <span> is not allowed"
+---
+# Title
+
+text <span>x</span> text

internal/rules/MDS041-no-inline-html/bad/self-closing-br.md

@@ -0,0 +1,11 @@
+---
+settings:
+  allow-comments: true
+diagnostics:
+  - line: 3
+    column: 5
+    message: "inline HTML <br> is not allowed"
+---
+# Title
+
+text<br/>more text

internal/rules/MDS041-no-inline-html/good/allowed-tag.md

@@ -0,0 +1,9 @@
+---
+settings:
+  allow:
+    - kbd
+  allow-comments: true
+---
+# Title
+
+Press <kbd>Enter</kbd> to continue.

internal/rules/MDS041-no-inline-html/good/autolink.md

@@ -0,0 +1,7 @@
+---
+settings:
+  allow-comments: true
+---
+# Title
+
+See <https://example.com> for details.