Create Cite element even if no matching reference in the biblio.

* Add ??? as fallback text for non-resolved citations.
* Biblio:  Put references (including a header at the end of
  the document, if one exists) inside a Div with class "references".
  This gives some control over styling of references, and allows
  scripts to manipulate them.
* Markdown writer:  Print markdown citation codes, and disable
  printing of references, if `citations` extension is enabled.

NOTE:  It would be good to improve what citeproc-hs does for
a nonexistent key.

4 files changed, 68 insertions, 46 deletions

diff --git a/tests/Tests/Old.hs b/tests/Tests/Old.hs
index 0ba240084..8609781d0 100644
--- a/tests/Tests/Old.hs
+++ b/tests/Tests/Old.hs
@@ -196,7 +196,7 @@ markdownCitationTests
      ++ [test "natbib" wopts "markdown-citations.txt"
          "markdown-citations.txt"]
   where
-    ropts             = ["-r", "markdown", "-w", "markdown", "--bibliography",
+    ropts             = ["-r", "markdown", "-w", "markdown-citations", "--bibliography",
                          "biblio.bib", "--no-wrap"]
     wopts             = ["-r", "markdown", "-w", "markdown", "--no-wrap", "--natbib"]
     styleToTest style = test style (ropts ++ ["--csl", style ++ ".csl"])
diff --git a/tests/markdown-citations.chicago-author-date.txt b/tests/markdown-citations.chicago-author-date.txt
index de242300d..81d7482cb 100644
--- a/tests/markdown-citations.chicago-author-date.txt
+++ b/tests/markdown-citations.chicago-author-date.txt
@@ -1,9 +1,9 @@
 Pandoc with citeproc-hs
 =======================
 
--   [@nonexistent]
+-   ([CSL BIBLIOGRAPHIC DATA ERROR: reference "nonexistent" not found.])
 
--   @nonexistent
+-    ([CSL BIBLIOGRAPHIC DATA ERROR: reference "nonexistent" not found.])
 
 -   Doe (2005) says blah.
 
@@ -29,15 +29,21 @@ Pandoc with citeproc-hs
 
 -   With some markup (*see* Doe 2005, 32).
 
+<div class="references">
+
 References
 ==========
 
+“Nonexistent Not Found!”
+
 Doe, John. 2005. *First Book*. Cambridge: Cambridge University Press.
 
 ———. 2006. “Article.” *Journal of Generic Studies* 6: 33–34.
 
 Doe, John, and Jenny Roe. 2007. “Why Water Is Wet.” In *Third Book*, edited by Sam Smith. Oxford: Oxford University Press.
 
+</div>
+
 [^1]: Doe and Roe (2007, 12) and a citation without locators (Doe and Roe 2007).
 
 [^2]: Some citations (see Doe 2005, chap. 3; Doe and Roe 2007; Doe 2006).
diff --git a/tests/markdown-citations.ieee.txt b/tests/markdown-citations.ieee.txt
index a397e3f38..4085a7c63 100644
--- a/tests/markdown-citations.ieee.txt
+++ b/tests/markdown-citations.ieee.txt
@@ -1,45 +1,51 @@
 Pandoc with citeproc-hs
 =======================
 
--   [@nonexistent]
+-   []
 
--   @nonexistent
+-   
 
--   Reference 1 says blah.
+-   Reference 2 says blah.
 
--   Reference 1 says blah.
+-   Reference 2 says blah.
 
--   Reference 1 says blah.
+-   Reference 2 says blah.
 
--   Reference 1 [3] says blah.
+-   Reference 2 [4] says blah.
 
 -   In a note.[^1]
 
--   A citation group [1], [3].
+-   A citation group [2], [4].
 
--   Another one [1].
+-   Another one [2].
 
 -   And another one in a note.[^2]
 
--   Citation with a suffix and locator [1].
+-   Citation with a suffix and locator [2].
 
--   Citation with suffix only [1].
+-   Citation with suffix only [2].
 
 -   Now some modifiers.[^3]
 
--   With some markup [1].
+-   With some markup [2].
+
+<div class="references">
 
 References
 ==========
 
-[1] J. Doe, *First Book*. Cambridge: Cambridge University Press, 2005.
+[1]“nonexistent not found!” .
+
+[2] J. Doe, *First Book*. Cambridge: Cambridge University Press, 2005.
+
+[3] J. Doe, “Article,” *Journal of Generic Studies*, vol. 6, pp. 33–34, 2006.
 
-[2] J. Doe, “Article,” *Journal of Generic Studies*, vol. 6, pp. 33–34, 2006.
+[4] J. Doe and J. Roe, “Why Water Is Wet,” in *Third Book*, S. Smith, Ed. Oxford: Oxford University Press, 2007.
 
-[3] J. Doe and J. Roe, “Why Water Is Wet,” in *Third Book*, S. Smith, Ed. Oxford: Oxford University Press, 2007.
+</div>
 
-[^1]: Reference 3 and a citation without locators [3].
+[^1]: Reference 4 and a citation without locators [4].
 
-[^2]: Some citations [1–3].
+[^2]: Some citations [2–4].
 
-[^3]: Like a citation without author: [1], and now Doe with a locator [2].
+[^3]: Like a citation without author: [2], and now Doe with a locator [3].
diff --git a/tests/markdown-citations.mhra.txt b/tests/markdown-citations.mhra.txt
index d33a1b94b..01d9c45ca 100644
--- a/tests/markdown-citations.mhra.txt
+++ b/tests/markdown-citations.mhra.txt
@@ -1,33 +1,35 @@
 Pandoc with citeproc-hs
 =======================
 
--   [@nonexistent]
+-   [^1]
 
--   @nonexistent
+-   [^2]
 
--   John Doe[^1] says blah.
+-   John Doe[^3] says blah.
 
--   Doe[^2] says blah.
+-   Doe[^4] says blah.
 
--   Doe[^3] says blah.
+-   Doe[^5] says blah.
 
--   Doe[^4] says blah.
+-   Doe[^6] says blah.
 
--   In a note.[^5]
+-   In a note.[^7]
 
--   A citation group.[^6]
+-   A citation group.[^8]
 
--   Another one.[^7]
+-   Another one.[^9]
 
--   And another one in a note.[^8]
+-   And another one in a note.[^10]
 
--   Citation with a suffix and locator.[^9]
+-   Citation with a suffix and locator.[^11]
 
--   Citation with suffix only.[^10]
+-   Citation with suffix only.[^12]
 
--   Now some modifiers.[^11]
+-   Now some modifiers.[^13]
 
--   With some markup.[^12]
+-   With some markup.[^14]
+
+<div class="references">
 
 References
 ==========
@@ -38,26 +40,34 @@ Doe, John, ‘Article’, *Journal of Generic Studies*, 6 (2006), 33–34.
 
 Doe, John, and Jenny Roe, ‘Why Water Is Wet’, in *Third Book*, ed. by Sam Smith (Oxford: Oxford University Press, 2007).
 
-[^1]: *First Book* (Cambridge: Cambridge University Press, 2005).
+‘Nonexistent Not Found!’.
+
+</div>
+
+[^1]: [CSL BIBLIOGRAPHIC DATA ERROR: reference "nonexistent" not found.].
+
+[^2]: [CSL STYLE ERROR: reference with no printed form.].
+
+[^3]: *First Book* (Cambridge: Cambridge University Press, 2005).
 
-[^2]: *First Book*, p. 30.
+[^4]: *First Book*, p. 30.
 
-[^3]: *First Book*, p. 30, with suffix.
+[^5]: *First Book*, p. 30, with suffix.
 
-[^4]: *First Book*; ‘Article’, *Journal of Generic Studies*, 6 (2006), 33–34 (p. 30); see also John Doe and Jenny Roe, ‘Why Water Is Wet’, in *Third Book*, ed. by Sam Smith (Oxford: Oxford University Press, 2007).
+[^6]: *First Book*; ‘Article’, *Journal of Generic Studies*, 6 (2006), 33–34 (p. 30); see also John Doe and Jenny Roe, ‘Why Water Is Wet’, in *Third Book*, ed. by Sam Smith (Oxford: Oxford University Press, 2007).
 
-[^5]: Doe and Roe, p. 12 and a citation without locators Doe and Roe.
+[^7]: Doe and Roe, p. 12 and a citation without locators Doe and Roe.
 
-[^6]: See Doe, *First Book*, chap. 3; also Doe and Roe, pp. 34–35.
+[^8]: See Doe, *First Book*, chap. 3; also Doe and Roe, pp. 34–35.
 
-[^7]: See Doe, *First Book*, pp. 34–35.
+[^9]: See Doe, *First Book*, pp. 34–35.
 
-[^8]: Some citations see Doe, *First Book*, chap. 3; Doe and Roe; Doe, ‘Article’, 33–34.
+[^10]: Some citations see Doe, *First Book*, chap. 3; Doe and Roe; Doe, ‘Article’, 33–34.
 
-[^9]: Doe, *First Book*, pp. 33, 35–37, and nowhere else.
+[^11]: Doe, *First Book*, pp. 33, 35–37, and nowhere else.
 
-[^10]: Doe, *First Book* and nowhere else.
+[^12]: Doe, *First Book* and nowhere else.
 
-[^11]: Like a citation without author: *First Book*, and now Doe with a locator ‘Article’, 33–34 (p. 44).
+[^13]: Like a citation without author: *First Book*, and now Doe with a locator ‘Article’, 33–34 (p. 44).
 
-[^12]: *See* Doe, *First Book*, p. 32.
+[^14]: *See* Doe, *First Book*, p. 32.