feat: Add basic support for bibliographic citations

Based on SILE 0.15.7 new CSL support.

README.md

@@ -153,6 +153,7 @@ This is but an overview. For more details, please refer to the provided example
 - Raw inline HTML convenience subset in Markdown
 - Advanced use of symbols in Djot (variable substitution ,and templating)
 - Advanced configuration (e.g. Markdown variants, headings shifting, etc.)
+- Bibliography citations (when appropriate support is enabled)
 
 ## Use with the resilient collection
 

examples/extra-styles.dj

@@ -57,3 +57,12 @@ class:registerCommand("Initial", function (_, content)
   SILE.call("dropcap", { lines = lines, family = family, color = color, join = true }, { letter })
 end)
 ```
+
+```=sile
+% Chicken and egg problem: resilient.sile will support loading bibliographies
+% in master documents, but relies on markdown.sile as dependency for references
+% in content files.
+% So this is a workaround to load the bibliography here, be able to release a
+% new version of markdown.sile and move forward with the development.
+\loadbibliography[file=examples/markdown-djot.bib]
+```

examples/markdown-djot.bib

@@ -0,0 +1,23 @@
+@book{sile,
+  title        = {The SILE Book},
+  author       = {Cozens, Simon and Maclennan, Caleb and Nicole, Olivier and Willis, Didier},
+  year         = {2014–202X},
+}
+
+@book{sile:willis2021,
+  title        = {The re·sil·ient collection of classes & packages for SILE: User Guide},
+  author       = {Willis, Didier},
+  year         = {2021–},
+}
+
+@book{sile:willis2022,
+  title        = {Markdown and Djot to PDF with SILE: Ultimate Guide & Showcase Document},
+  author       = {Willis, Didier},
+  year         = {2022–},
+}
+
+@book{sile:willis2024,
+  title        = {SILE and the Hydra of Maths. Showcase & Critical Assessment 2024},
+  author       = {Willis, Didier},
+  year         = {2024},
+}

examples/sile-and-djot.dj

@@ -501,7 +501,7 @@ $$`\pi=\sum_{k=0}^\infty\frac{1}{16^k}(\frac{4}{8k+1} − \frac{2}{8k+4} − \fr
 
 Attributes are passed through to SILE.
 In display math mode, you can number equations using the default counter (`numbered=true`), a named counter (`counter=name`), or a custom value (`number=...`).
-$$`e^{i\phi} = \mi{cos} \phi + i \mi{sin} \phi`{numbered=true}
+$$`e^{i\phi} = \cos \phi + i \sin \phi`{numbered=true}
 
 ### Footnote calls
 
@@ -517,6 +517,25 @@ A footnote call[^djot-some-fn] is marked...
 
 [^djot-some-fn]: An example footnote.
 
+### Bibliographic citations
+
+Djot does not officially support citations at the moment.
+This implementation, however, recognizes a simplified subset of the Pandoc citation syntax.
+
+{custom-style=CodeBlock}
+:::
+```
+I wrote a whole book on mathematics with SILE [@sile:willis2024].
+... in a "master document" [@sile:willis2021, part 1].
+... _The SILE Book_ for more information [@sile, chapter 5].
+```
+:::
+
+I wrote whole book on mathematics with SILE [@sile:willis2024].
+
+How to load bibliographies and configure citation styles is beyond the scope of this manual.
+If you are using the resilient collection, the most natural way to do this in a "master document" [@sile:willis2021, part 1].
+Note that support for biblibraphies in SILE is an experimental feature, so you may also want to check _The SILE Book_ for more information [@sile, chapter 5].
 
 {#djot-symbols}
 ### Symbols
@@ -809,8 +828,8 @@ Any further blocks included in the item are assumed to be the definition.
 
 Block attributes are passed to the underlying definition environment.
 When not using a supporting class or package, the converter uses its own fallback method, with hard-coded styling (e.g. the term is typeset in boldface).
-When using the *resilient* classes, the converter uses the *resilient.defn* environment, and the `variant` option may thus be used to switch to an alternate style.[^djot-defn-variant]
-For the purpose of illustration, let's say you have a "Custom" variant with an _ad hoc_ style.
+When using the *resilient* classes, the *resilient.defn* environment is loaded, and the `variant` option may thus be used to switch to an alternate style.[^djot-defn-variant]
+As an example, let's say you have a "Custom" variant with an _ad hoc_ style.
 
 {custom-style=CodeBlock}
 :::
@@ -996,7 +1015,7 @@ The `render` attribute can be set to `false` to prevent this behavior, and enfor
     For instance, the image below is produced with `{.dot width="3.5cm" layout=twopi}`.
 
     :::
-    {width="3.5cm" layout=twopi}
+    {width="3cm" layout=twopi}
     ```dot
     graph {
       node [fillcolor="lightskyblue:darkcyan" style=filled gradientangle=270]
@@ -1009,7 +1028,7 @@ The `render` attribute can be set to `false` to prevent this behavior, and enfor
     :::
     ^ An example of a rendered DOT graph.
 
-    The original DOT description used in the code block is shown hereafter.
+    The original DOT description is shown hereafter.
 
     {custom-style=CodeBlock}
     :::
@@ -1239,7 +1258,7 @@ Language changes within the text are supported, on either blocks or inline
 elements.
 It relies on the `lang` key-value attribute, where the value is a BCP47 language code.
 It is not much visible below, obviously, but the language setting affects the hyphenation and other properties.
-In the case of French, for instance, you can see the special thin space before the exclamation point, the use of appropriate quotation marks, and the internal spacing around quoted text:
+In the case of French, for instance, you can see the thin space before the exclamation point, the use of appropriate quotation marks, and the internal spacing around quoted text:
 
 {lang=fr}
 > Cette citation est en français!
@@ -1331,7 +1350,6 @@ Since it's possible to have unused footnote definitions, let's craft one as show
 
 When encountering a symbol, this converter looks for such a footnote and expands its content.
 It works with inline elements as shown above, but also with full blocks, provided the symbol is the only element in a paragraph of its own.
-
 Of course, these pseudo-footnotes[^djot-pseudo-footnotes] can in turn contain symbols, which get replaced too.
 
 

examples/sile-and-markdown-manual-styles.yml

@@ -1,25 +1,4 @@
 
-defn-term-Custom:
-  inherit: "defn-base"
-  origin: "resilient.defn"
-  style:
-    font:
-      features: "+smcp"
-    paragraph:
-      after:
-        vbreak: false
-      before:
-        skip: "smallskip"
-
-defn-desc-Custom:
-  inherit: "defn-desc"
-  style:
-    paragraph:
-      after:
-        skip: "smallskip"
-      before:
-        vbreak: false
-
 CodeBlock:
   origin: "resilient.book"
   style:
@@ -44,22 +23,12 @@ CoverCredit:
 CustomDroppedInitial:
   origin: "resilient.book"
   style:
+    color: "#66a0b3"
     font:
       family: "Zallman Caps"
-    color: "#66a0b3"
     special:
       lines: 3
 
-FramedPara:
-  origin: "resilient.book"
-  style:
-    paragraph:
-      after:
-        skip: "medskip"
-      align: "fancy-framed"
-      before:
-        skip: "medskip"
-
 Difference:
   style:
     font:
@@ -71,6 +40,16 @@ Difference:
       before:
         skip: "smallskip"
 
+FramedPara:
+  origin: "resilient.book"
+  style:
+    paragraph:
+      after:
+        skip: "medskip"
+      align: "fancy-framed"
+      before:
+        skip: "medskip"
+
 blockquote:
   origin: "resilient.book"
   style:
@@ -104,6 +83,46 @@ bookmatter-copyright:
     paragraph:
       align: "noparindent"
 
+bookmatter-cover-author:
+  inherit: "bookmatter-coverpage"
+  origin: "resilient.bookmatters"
+  style:
+    font:
+      size: "16pt"
+    properties:
+      case: "upper"
+
+bookmatter-cover-publisher:
+  inherit: "bookmatter-coverpage"
+  origin: "resilient.bookmatters"
+  style:
+
+bookmatter-cover-subtitle:
+  inherit: "bookmatter-coverpage"
+  origin: "resilient.bookmatters"
+  style:
+    font:
+      size: "16pt"
+    paragraph:
+      after:
+        skip: "5%fh"
+
+bookmatter-cover-title:
+  inherit: "bookmatter-coverpage"
+  origin: "resilient.bookmatters"
+  style:
+    font:
+      size: "20pt"
+    paragraph:
+      after:
+        skip: "5%fh"
+      before:
+        skip: "30%fh"
+
+bookmatter-coverpage:
+  origin: "resilient.bookmatters"
+  style:
+
 bookmatter-halftitle:
   origin: "resilient.bookmatters"
   style:
@@ -179,6 +198,15 @@ defn-desc:
       before:
         vbreak: false
 
+defn-desc-Custom:
+  inherit: "defn-desc"
+  style:
+    paragraph:
+      after:
+        skip: "smallskip"
+      before:
+        vbreak: false
+
 defn-term:
   inherit: "defn-base"
   origin: "resilient.defn"
@@ -191,6 +219,18 @@ defn-term:
       before:
         skip: "smallskip"
 
+defn-term-Custom:
+  inherit: "defn-base"
+  origin: "resilient.defn"
+  style:
+    font:
+      features: "+smcp"
+    paragraph:
+      after:
+        vbreak: false
+      before:
+        skip: "smallskip"
+
 dropcap:
   origin: "resilient.book"
   style:
@@ -239,6 +279,16 @@ epigraph-text:
     paragraph:
       align: "justify"
 
+eqno:
+  origin: "resilient.book"
+  style:
+    numbering:
+      after:
+        text: ")"
+      before:
+        text: "("
+      display: "arabic"
+
 fancytoc-base:
   style:
 

examples/sile-and-markdown.md

@@ -507,6 +507,24 @@ They are introduced with directly with the caret `^`, immediately followed by th
 
 :::
 
+### Bibliographic citations
+
+This implementation recognizes a simplified subset of the Pandoc citation syntax, aligned with what we also support in Djot.
+
+::: {custom-style=CodeBlock}
+```
+I wrote a whole book on mathematics with SILE [@sile:willis2024].
+... in a "master document" [@sile:willis2021, part 1].
+... _The SILE Book_ for more information [@sile, chapter 5].
+```
+:::
+
+I wrote whole book on mathematics with SILE [@sile:willis2024].
+
+How to load bibliographies and configure citation styles is beyond the scope of this manual.
+If you are using the resilient collection, the most natural way to do this in a "master document" [@sile:willis2021, part 1].
+Note that support for biblibraphies in SILE is an experimental feature, so you may also want to check _The SILE Book_ for more information [@sile, chapter 5].
+
 ### Symbols
 
 ::: {custom-style=Difference}
@@ -1054,7 +1072,8 @@ This converter recognizes a few specific attributes on divs:
 ### Horizontal dividers
 
 In standard Markdown, a line containing a row of three or more asterisks, dashes, or underscores (optionally separated by spaces) are supposed to produce a horizontal rule. 
-This converter however slightly deviates from that simple specification^[And also from Pandoc, therefore. Quite obviously, the `\autodoc:package{pandocast}`{=sile} package will also only show horizontal rules.],
+This converter however slightly deviates from that simple specification^[And also from Pandoc.
+Our `\autodoc:package{pandocast}`{=sile} package will only show horizontal rules.],
 for the mere reason that such a horizontal rule is seldom typographically sound in many contexts.
 
 Three asterisks produce a centered asterism.

inputters/djot.lua

@@ -759,6 +759,11 @@ function Renderer:math (node)
   return createCommand("markdown:internal:math", options, { node.s }, node_pos(node))
 end
 
+function Renderer:naive_citations (node)
+  local pos = node_pos(node)
+  return utils.naiveCitations(node.s, pos)
+end
+
 -- SILE INPUTTER LOGIC
 
 local base = require("inputters.base")

inputters/markdown.lua

@@ -267,6 +267,10 @@ local function SileAstWriter (writerOps, renderOps)
     return createCommand("markdown:internal:math" , { mode = mode }, { text })
   end
 
+  writer.naive_citations = function (rawcites)
+    return utils.naiveCitations(rawcites)
+  end
+
   -- Final AST conversion logic.
   --   The lunamark "AST" is made of "ropes":
   --     "A rope is an array whose elements may be ropes, strings, numbers,
@@ -366,11 +370,15 @@ parsers.lineof = function (c)
 
 local function customSyntax (writer, options)
   return function (syntax)
+    -- Re-create the horizontal rule syntax to use our modified lineof
+    -- with a capture.
     syntax.HorizontalRule = (parsers.lineof(parsers.asterisk)
                             + parsers.lineof(parsers.dash)
                             + parsers.lineof(parsers.underscore)
                             ) / writer.hrule
 
+    -- Extend the smart typography syntax to recognize primes and double primes
+    -- after digits.
     if options.smart_primes then
       syntax.Smart = lpeg.P("\"") * lpeg.B(parsers.digit*1) / function ()
                         return "″" -- double primes
@@ -380,6 +388,10 @@ local function customSyntax (writer, options)
                       end
                    + syntax.Smart
     end
+    -- Override the citation syntax to use our own raw citations writer
+    syntax.Citations = lpeg.P("[")
+                     * lpeg.C(lpeg.P("@") *(lpeg.P(1) - lpeg.P("]"))^1)
+                     * lpeg.P("]")  / writer.naive_citations
     return syntax
   end
 end
@@ -430,6 +442,7 @@ function inputter:parse (doc)
     line_blocks = true,
     escaped_line_breaks = true,
     tex_math_dollars = true,
+    citations = true,
   }
   for k, v in pairs(self.options) do
     -- Allow overriding known options