feat(config): custom_wiki2html external converter + base_url for RSS (P2)

Add three per-wiki HtmlConfig keys mirroring vimwiki globals:

- custom_wiki2html / custom_wiki2html_args: when set, export shells out
  to the external converter via `sh -c` with vimwiki's exact arg order
  (<cmd> <force> <syntax> <ext> <out_dir> <in_file> <css> <tpl_path>
  <tpl_default> <tpl_ext> <root_path> <args>, `-` for empty optionals)
  instead of the built-in renderer.
- base_url: when set, diary RSS item + channel links become
  <base_url><diary_rel_path>/<date>.html instead of file:// URIs.

write_page() gains a `force` flag threaded through export_current (false),
export_all (its own flag) and the did_save auto-export path (false).

Tests: write_page_invokes_custom_wiki2html_converter,
write_rss_uses_base_url_for_public_links (html_export.rs), config
round-trip + defaults (index_and_config.rs). Docs: README, doc/nuwiki.txt,
lua config comment, vimwiki-gap.md item ticked.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/nuwiki-lsp/tests/html_export.rs

@@ -428,7 +428,7 @@ fn write_page_writes_html_to_disk() {
     let mut c = WikiConfig::from_root(root.clone());
     c.html = HtmlConfig::from_root(&root);
     let ast = parse("= Hello =\nworld\n");
-    let outcome = nuwiki_lsp::commands::export_ops::write_page(&ast, "Hello", &c).unwrap();
+    let outcome = nuwiki_lsp::commands::export_ops::write_page(&ast, "Hello", &c, false).unwrap();
     assert_eq!(outcome.page, "Hello");
     assert!(outcome.output_path.exists());
     let body = std::fs::read_to_string(&outcome.output_path).unwrap();
@@ -442,7 +442,7 @@ fn write_page_creates_subdirs() {
     c.html = HtmlConfig::from_root(&root);
     let ast = parse("= Daily =\n");
     let outcome =
-        nuwiki_lsp::commands::export_ops::write_page(&ast, "diary/2026-05-11", &c).unwrap();
+        nuwiki_lsp::commands::export_ops::write_page(&ast, "diary/2026-05-11", &c, false).unwrap();
     assert!(outcome.output_path.exists());
     assert!(outcome
         .output_path
@@ -463,7 +463,7 @@ fn write_page_uses_template_file_when_present() {
     )
     .unwrap();
     let ast = parse("%title T\n= H =\nbody\n");
-    let outcome = nuwiki_lsp::commands::export_ops::write_page(&ast, "P", &c).unwrap();
+    let outcome = nuwiki_lsp::commands::export_ops::write_page(&ast, "P", &c, false).unwrap();
     let body = std::fs::read_to_string(outcome.output_path).unwrap();
     assert!(body.starts_with("<x>T|"));
     assert!(body.ends_with("</x>"));
@@ -518,6 +518,60 @@ fn write_rss_emits_valid_xml_with_entries() {
     let i11 = xml.find("2026-05-11").unwrap();
     let i10 = xml.find("2026-05-10").unwrap();
     assert!(i11 < i10);
+    // No base_url → item links keep the file:// URI.
+    assert!(xml.contains("<link>file:///tmp/diary/2026-05-11.wiki</link>"));
+}
+
+#[test]
+fn write_rss_uses_base_url_for_public_links() {
+    use nuwiki_lsp::diary::DiaryEntry;
+    use tower_lsp::lsp_types::Url;
+
+    let root = temp_root("rss_base");
+    let mut c = WikiConfig::from_root(root.clone());
+    c.html = HtmlConfig::from_root(&root);
+    c.html.base_url = "https://example.com/wiki/".into();
+    c.diary_rel_path = "diary".into();
+    let entries = vec![DiaryEntry {
+        date: DiaryDate::from_ymd(2026, 5, 11).unwrap(),
+        uri: Url::parse("file:///tmp/diary/2026-05-11.wiki").unwrap(),
+    }];
+    let path = nuwiki_lsp::commands::export_ops::write_rss(&c, &entries).unwrap();
+    let xml = std::fs::read_to_string(&path).unwrap();
+    // Channel + item links use the public base URL, not file://.
+    assert!(xml.contains("<link>https://example.com/wiki/</link>"));
+    assert!(xml.contains("<link>https://example.com/wiki/diary/2026-05-11.html</link>"));
+    assert!(xml.contains("<guid>https://example.com/wiki/diary/2026-05-11.html</guid>"));
+    assert!(!xml.contains("file:///tmp/diary"));
+}
+
+#[test]
+fn write_page_invokes_custom_wiki2html_converter() {
+    let root = temp_root("custom_w2h");
+    let mut c = WikiConfig::from_root(root.clone());
+    c.html = HtmlConfig::from_root(&root);
+    // Source file must exist on disk — the converter receives its path.
+    std::fs::write(root.join("Hello.wiki"), "= Hello =\nworld\n").unwrap();
+    // A tiny shell "converter": writes a marker into the output path it is told
+    // to produce. nuwiki appends args positionally after `_` ($0), so
+    // $1=force, $2=syntax, $3=ext, $4=output_dir, $5=input_file, …
+    let script = "mkdir -p \"$4\" && printf 'CUSTOM:%s' \"$5\" > \"$4\"/Hello.html";
+    c.html.custom_wiki2html = format!("sh -c {} _", shell_words_quote(script));
+    let outcome =
+        nuwiki_lsp::commands::export_ops::write_page(&parse("= Hello =\n"), "Hello", &c, true)
+            .unwrap();
+    assert_eq!(outcome.page, "Hello");
+    assert!(outcome.output_path.exists(), "converter must produce output");
+    let body = std::fs::read_to_string(&outcome.output_path).unwrap();
+    assert!(
+        body.starts_with("CUSTOM:"),
+        "marker from converter, got {body}"
+    );
+}
+
+/// Minimal single-quote shell escaping for the test command above.
+fn shell_words_quote(s: &str) -> String {
+    format!("'{}'", s.replace('\'', "'\\''"))
 }
 
 // ===== COMMANDS list completeness =====

crates/nuwiki-lsp/tests/index_and_config.rs

@@ -284,6 +284,10 @@ fn defaults_carry_vimwiki_per_wiki_keys() {
     assert_eq!(cfg.links_header, "Generated Links");
     assert_eq!(cfg.tags_header, "Generated Tags");
     assert_eq!(cfg.listsym_rejected, "-");
+    // No external converter / public base URL by default.
+    assert_eq!(cfg.html.custom_wiki2html, "");
+    assert_eq!(cfg.html.custom_wiki2html_args, "");
+    assert_eq!(cfg.html.base_url, "");
 }
 
 #[test]
@@ -312,6 +316,9 @@ fn raw_wiki_parses_every_new_key() {
             "links_header": "All Pages",
             "tags_header": "Tag Index",
             "tags_header_level": 3,
+            "custom_wiki2html": "~/bin/my_wiki2html.sh",
+            "custom_wiki2html_args": "--flag",
+            "base_url": "https://example.com/wiki/",
         }],
     }));
     let w = &cfg.wikis[0];
@@ -338,6 +345,11 @@ fn raw_wiki_parses_every_new_key() {
     assert_eq!(w.links_header_level, 1); // unspecified → default
     assert_eq!(w.tags_header, "Tag Index");
     assert_eq!(w.tags_header_level, 3);
+    // custom_wiki2html keeps the literal command string (tilde-expansion is
+    // the converter's job, not ours); args + base_url round-trip verbatim.
+    assert_eq!(w.html.custom_wiki2html, "~/bin/my_wiki2html.sh");
+    assert_eq!(w.html.custom_wiki2html_args, "--flag");
+    assert_eq!(w.html.base_url, "https://example.com/wiki/");
 
     // The parsed keys drive a date-mode, Sunday-start diary calendar:
     // a weekly note is the week-start date (YYYY-MM-DD), stepping ±7 days.