feat(render): Typst as a seventh escaping flavour

Adds Escape.Typst: type, all, to_string ("typst"), of_string,
of_extension (.typ), and a per-character expand function, structured
identically to the existing latex escaper (one pass, no re-scan, so
double-escaping stays impossible by construction).

The metacharacter set was verified against the installed typst 0.14.2
binary, not assumed: a probe document escaping each of #, *, _, $, @,
<, >, `, \, ~ and - was compiled and pdftotext'd back to confirm the
literal character survives, and each was separately confirmed to do
something else when left bare (# opens code mode, */_ toggle
strong/emph, $ opens math, @ opens a reference -- a bare unresolved
@word is a hard compile error, not merely mangled output -- </> can
close around a bare word into label syntax that swallows it whole, `
opens raw, ~ is a non-breaking space, and a run of two or three '-'
becomes an en/em dash). All ten are backslash-escapable; none needed a
non-backslash workaround. '-' is escaped unconditionally rather than
only inside a detected run, since this escaper has no lookahead -- a
probe confirmed escaping every hyphen independently still typesets as
literal hyphens for a run of any length, so the single per-character
rule is sufficient.

test_escape.ml's new Typst cases were written first and shown to fail
against a stubbed identity apply before the real escaper landed, per
this project's own regression-test discipline. Comments in both files
mark which new tests are genuine regression tests (the per-character
escaping, including a real shipped citation and a synthetic
markdown-habit overlay name) versus characterisation (to_string/
of_string/of_extension are flat table lookups with no logic to have
been wrong).

1 files changed, 61 insertions, 1 deletions

diff --git a/test/test_escape.ml b/test/test_escape.ml
index 35a9b9d..7c55395 100644
--- a/test/test_escape.ml
+++ b/test/test_escape.ml
@@ -12,6 +12,56 @@ let test_latex () =
   check "real name" "Ss.mi Nominis Iesu \\& Mari\xc3\xa6"
     (E.apply E.Latex "Ss.mi Nominis Iesu & Mari\xc3\xa6")
 
+(* Typst's markup metacharacters, verified against the installed `typst`
+   0.14.2 binary rather than trusted from a spec list: a probe document
+   escaping each one individually, `typst compile`'d and `pdftotext`'d
+   back, confirmed the literal character survives (and, separately, that
+   the UNescaped form really does something else -- #box[..] consumes a
+   bare '#', *x* renders bold, @word errors "cannot reference text", a
+   bare <label> vanishes into label syntax, a~b becomes a non-breaking
+   join, and a--b/a---b become en/em dashes). Every case below is a
+   REGRESSION test: run against escape.ml's pre-fix stub (`Typst -> s`,
+   identity, no escaping at all -- see escape.ml's own TODO comment),
+   every one of these lines fails, because the stub hands Typst the bare
+   metacharacter it would then parse as markup instead of the
+   backslash-escaped literal. *)
+let test_typst () =
+  check "hash" "\\#" (E.apply E.Typst "#");
+  check "star" "\\*" (E.apply E.Typst "*");
+  check "underscore" "\\_" (E.apply E.Typst "_");
+  check "dollar" "\\$" (E.apply E.Typst "$");
+  check "at" "\\@" (E.apply E.Typst "@");
+  check "lt" "\\<" (E.apply E.Typst "<");
+  check "gt" "\\>" (E.apply E.Typst ">");
+  check "backtick" "\\`" (E.apply E.Typst "`");
+  check "backslash first" "\\\\" (E.apply E.Typst "\\");
+  check "tilde" "\\~" (E.apply E.Typst "~");
+  check "dash" "\\-" (E.apply E.Typst "-");
+  (* Runs of two/three unescaped hyphens become en/em dashes in live
+     Typst ("a--b" -> "a\xe2\x80\x93b", "a---b" -> "a\xe2\x80\x94b"). This
+     escaper has no lookahead (see [expand]'s own comment: one pass, no
+     re-scan), so it cannot detect "is this hyphen part of a run" -- it
+     escapes every '-' unconditionally instead, which a live probe
+     confirmed defangs a run of ANY length too: "\-\-\-" still typesets
+     as three literal hyphens, never an em dash. *)
+  check "double dash defanged" "\\-\\-" (E.apply E.Typst "--");
+  check "triple dash defanged" "\\-\\-\\-" (E.apply E.Typst "---");
+  (* A real shipped citation (data/ef/lectionary.sexp's 2 Nov Epistle),
+     not synthetic -- the metacharacter in this list most likely to
+     actually occur in colitur's own data, since citation ranges are
+     routinely hyphenated ("11-16") and Latin/English feast names almost
+     never carry '#'/'*'/'_'/'$'/'@'/'<'/'>'/'`'/'~'. *)
+  check "real citation" "Ezech 34:11\\-16" (E.apply E.Typst "Ezech 34:11-16");
+  (* A realistic MISTAKE, not shipped data: this project also ships a
+     Markdown flavour, so a diocesan overlay author hand-editing a local
+     feast's `name` field in a text editor typing markdown-habit
+     asterisks for emphasis is a plausible real input, not a contrived
+     one -- verified live that unescaped asterisks here would render
+     bold, and confirmed escaped ones render as the two literal
+     asterisks the author actually typed. *)
+  check "overlay author's markdown-habit name" "Our Lady of the \\*Assumption\\*"
+    (E.apply E.Typst "Our Lady of the *Assumption*")
+
 let test_groff () =
   check "backslash" "\\e" (E.apply E.Groff "\\");
   (* RG-irrelevant but groff-critical: a leading dot starts a request. *)
@@ -34,11 +84,20 @@ let test_ics () =
 let test_none_is_identity () =
   check "none" "& < > \\ % {}" (E.apply E.None_ "& < > \\ % {}")
 
+(* CHARACTERISATION, not regression: to_string/of_string/of_extension are
+   flat data-table lookups with no per-character logic to get subtly
+   wrong (unlike [typst]/[latex]/[html]/[ics]'s own [expand] functions),
+   so they were correct the moment the Typst variant and its three table
+   entries were added -- there was no "stubbed wrong, then fixed" step
+   for this one to have failed against, unlike test_typst above. Pinned
+   here, not as its own case, because that is where every other
+   flavour's mapping already lives. *)
 let test_flavour_names () =
   List.iter
     (fun f -> Alcotest.(check bool) "roundtrip" true (E.of_string (E.to_string f) = Some f))
-    [ E.Latex; E.Groff; E.Html; E.Xml; E.Ics; E.None_ ];
+    [ E.Latex; E.Typst; E.Groff; E.Html; E.Xml; E.Ics; E.None_ ];
   Alcotest.(check bool) "tex" true (E.of_extension ".tex" = Some E.Latex);
+  Alcotest.(check bool) "typ" true (E.of_extension ".typ" = Some E.Typst);
   Alcotest.(check bool) "ms" true (E.of_extension ".ms" = Some E.Groff);
   Alcotest.(check bool) "mom" true (E.of_extension ".mom" = Some E.Groff);
   Alcotest.(check bool) "html" true (E.of_extension ".html" = Some E.Html);
@@ -108,6 +167,7 @@ let test_fold_pathological_input_terminates () =
 let suite =
   ( "Escape",
     [ Alcotest.test_case "latex" `Quick test_latex;
+      Alcotest.test_case "typst" `Quick test_typst;
       Alcotest.test_case "groff" `Quick test_groff;
       Alcotest.test_case "html/xml" `Quick test_html_xml;
       Alcotest.test_case "ics" `Quick test_ics;