feat(panettone): render a subset of markdown in issue subjects r/2144

This is achieved by implementing a simple markdown renderer in CL which
has the following limitations:

* Only supports inline `code`, *emphasize 1*, _emphasize 2_ and
  ~~strikethrough~~.
* Does not support nested markup.

This allows for a relatively simple renderer which doesn't need to parse
markdown into a in-memory data structure first. The rendered result is
directly written to a stream to integrate well with cl-who which is also
reused for rendering tags and xml-escaping strings.

Fixes #90.

Change-Id: Ice88ed770b1fab6365f3b93e8663e25077befa0b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2389
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>
Reviewed-by: tazjin <mail@tazj.in>

2 files changed, 56 insertions, 1 deletions

diff --git a/web/panettone/test/inline-markdown_test.lisp b/web/panettone/test/inline-markdown_test.lisp
new file mode 100644
index 0000000000..2b6c3b8900
--- /dev/null
+++ b/web/panettone/test/inline-markdown_test.lisp
@@ -0,0 +1,54 @@
+(in-package :panettone.tests)
+(declaim (optimize (safety 3)))
+
+(defmacro inline-markdown-unit-test (name input expected)
+  `(test ,name
+     (is (equal
+           ,expected
+           (with-output-to-string (*standard-output*)
+             (render-inline-markdown ,input))))))
+
+(inline-markdown-unit-test
+  inline-markdown-typical-test
+  "hello _world_, here is ~~no~~ `code`!"
+  "hello <em>world</em>, here is <del>no</del> <code>code</code>!")
+
+(inline-markdown-unit-test
+  inline-markdown-two-emphasize-types-test
+  "_stress_ *this*"
+  "<em>stress</em> <em>this</em>")
+
+(inline-markdown-unit-test
+  inline-markdown-html-escaping-test
+  "<tag>öäü"
+  "&lt;tag&gt;&#246;&#228;&#252;")
+
+(inline-markdown-unit-test
+  inline-markdown-nesting-test
+  "`inside code *anything* goes`, but also ~~*here*~~"
+  "<code>inside code *anything* goes</code>, but also <del>*here*</del>")
+
+(inline-markdown-unit-test
+  inline-markdown-escaping-test
+  "A backslash \\\\ shows: \\*, \\_, \\` and \\~~"
+  "A backslash \\ shows: *, _, ` and ~~")
+
+(inline-markdown-unit-test
+  inline-markdown-nested-escaping-test
+  "`prevent \\`code\\` from ending, but never stand alone \\\\`"
+  "<code>prevent `code` from ending, but never stand alone \\</code>")
+
+(inline-markdown-unit-test
+  inline-markdown-escape-normal-tokens-test
+  "\\Normal tokens \\escaped?"
+  "\\Normal tokens \\escaped?")
+
+(inline-markdown-unit-test
+  inline-markdown-no-unclosed-tags-test
+  "A tag, once opened, _must be closed"
+  "A tag, once opened, <em>must be closed</em>")
+
+(inline-markdown-unit-test
+  inline-markdown-unicode-safe
+  "Does Unicode 👨‍👨‍👧‍👦 break \\👩🏾‍🦰 tokenization?"
+  "Does Unicode &#128104;&#8205;&#128104;&#8205;&#128103;&#8205;&#128102; break \\&#128105;&#127998;&#8205;&#129456; tokenization?")
diff --git a/web/panettone/test/package.lisp b/web/panettone/test/package.lisp
index 77ba1b00bb..d2a2f97420 100644
--- a/web/panettone/test/package.lisp
+++ b/web/panettone/test/package.lisp
@@ -1,2 +1,3 @@
 (defpackage :panettone.tests
-  (:use :cl :klatre :fiveam))
+  (:use :cl :klatre :fiveam
+        :panettone.inline-markdown))