mattcasters opened a new pull request, #7443:
URL: https://github.com/apache/hop/pull/7443
# Issue #7442 — Markdown preview: GFM table rendering
Recap for code reviewers.
## Summary
The Markdown file preview in the Hop file explorer
(`MarkDownExplorerFileTypeHandler.previewMarkdown()`) did not render GFM pipe
tables correctly. Tables appeared as plain paragraphs with literal `|`
characters instead of HTML `<table>` elements.
This change adds the required CommonMark extensions, registers them on the
parser and renderer, and adds table-specific CSS for both light and dark mode
previews.
## Problem
`previewMarkdown()` used the base CommonMark parser with no extensions:
```java
Parser parser = Parser.builder().build();
HtmlRenderer renderer = HtmlRenderer.builder().build();
```
CommonMark core does not support GFM tables. A report such as
`retail-dv-initial-report.md` (pipe tables with alignment markers like `---:`)
was parsed into eight `<p>| ... |</p>` blocks and zero `<table>` elements.
Headings, bold text, inline code, and lists rendered correctly; only
GFM-specific syntax was broken.
## Solution
### 1. Dependencies (`plugins/transforms/textfile/pom.xml`)
Three CommonMark extensions were added (all `provided` scope, version
`${commonmark.version}` = `0.29.0`):
| Artifact | Purpose |
|---|---|
| `commonmark-ext-gfm-tables` | Pipe tables and column alignment |
| `commonmark-ext-task-list-items` | `- [x]` / `- [ ]` task lists |
| `commonmark-ext-footnotes` | `[^1]` footnotes |
These match the existing pattern for `commonmark` core in the textfile
plugin.
### 2. Extension registration (`MarkDownExplorerFileTypeHandler.java`)
Extensions are configured once in a static list and passed to both builder
instances:
```java
private static final List<Extension> MARKDOWN_EXTENSIONS =
List.of(
TablesExtension.create(),
TaskListItemsExtension.create(),
FootnotesExtension.create());
Parser parser = Parser.builder().extensions(MARKDOWN_EXTENSIONS).build();
HtmlRenderer renderer =
HtmlRenderer.builder().extensions(MARKDOWN_EXTENSIONS).build();
```
Parser and HtmlRenderer are thread-safe when built this way, so the static
list is appropriate.
### 3. Table CSS in preview HTML
The inline preview stylesheet had no `table` rules. Shared layout rules were
added (full width, collapsed borders, padding, rounded corners), plus
mode-specific colors:
**Light mode**
- Table background: `#ffffff`
- Header background: `#f1f5f9`
- Borders: `#e2e8f0`
- Alternating rows: `#f8fafc`
**Dark mode**
- Table background: `#0f172a`
- Header background: `#1e293b`
- Borders: `#334155`
- Alternating rows: `#111827`
Colors follow the existing slate palette already used for body, code blocks,
and blockquotes.
## Files changed
| File | Change |
|---|---|
| `plugins/transforms/textfile/pom.xml` | +3 CommonMark extension
dependencies |
|
`plugins/transforms/textfile/src/main/java/.../MarkDownExplorerFileTypeHandler.java`
| Extension registration + table CSS |
**Diff size:** 2 files, +71 / −2 lines.
## Review focus
1. **Classpath / assembly** — Extension JARs use `provided` scope like
`commonmark` core. Confirm they are bundled into the Hop client distribution at
runtime (same mechanism as the existing `commonmark` dependency via the
textfile plugin).
2. **LICENSE** — If ASF release policy requires it, the static `LICENSE`
file may need entries for the three new extension artifacts (currently only
`commonmark` core is listed).
3. **Scope** — Only the explorer Markdown preview is updated.
`DocBuilder.markdownToHtml()` in `plugins/misc/documentation` still uses the
bare parser and would have the same table limitation if HTML doc generation is
expected to handle GFM tables.
4. **No new tests** — Existing `MarkDownExplorerFileTypeTest` covers
file-type metadata only, not preview rendering. Consider whether a small unit
test asserting `<table>` output for a pipe-table snippet is worth adding in a
follow-up.
## Manual verification
1. Build and start Hop GUI.
2. Open a `.md` file with GFM tables (e.g. a data-vault load report).
3. Click the preview toolbar button.
4. Confirm:
- Tables render as bordered HTML tables, not pipe-separated paragraphs.
- Header row has a distinct background.
- Alternating row shading is visible.
- Appearance is correct in both light and dark mode.
## Out of scope / known limitations
- No syntax highlighting for fenced code blocks (would need a separate
JS/CSS library).
- No `commonmark-ext-autolink` or `commonmark-ext-gfm-strikethrough` — bare
URLs and `~~strikethrough~~` still render as literal text.
- No `ul`/`ol` list styling added (lists were already readable).
- Documentation plugin HTML generation unchanged.
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