Merge pull request #1954 from mcmtroffaes/feature/citekey-firstchar-alphanum

Allow digit as first character of a citation key.

README

@@ -2733,7 +2733,7 @@ modifying CSL styles can be found at
 Citations go inside square brackets and are separated by semicolons.
 Each citation must have a key, composed of '@' + the citation
 identifier from the database, and may optionally have a prefix,
-a locator, and a suffix.  The citation key must begin with a letter
+a locator, and a suffix.  The citation key must begin with a letter, digit,
 or `_`, and may contain alphanumerics, `_`, and internal punctuation
 characters (`:.#$%&-+?<>~/`).  Here are some examples:
 

src/Text/Pandoc/Parsing.hs

@@ -1191,7 +1191,7 @@ citeKey = try $ do
   guard =<< notAfterString
   suppress_author <- option False (char '-' *> return True)
   char '@'
-  firstChar <- letter <|> char '_'
+  firstChar <- alphaNum <|> char '_'
   let regchar = satisfy (\c -> isAlphaNum c || c == '_')
   let internal p = try $ p <* lookAhead regchar
   rest <- many $ regchar <|> internal (oneOf ":.#$%&-+?<>~/")

tests/Tests/Readers/Markdown.hs

@@ -293,4 +293,26 @@ tests = [ testGroup "inline code"
                          , plain "b"
                          , plain "c" <> bulletList [plain "d"] ]
           ]
+        , testGroup "citations"
+          [ "simple" =:
+            "@item1" =?> para (cite [
+                Citation{ citationId      = "item1"
+                        , citationPrefix  = []
+                        , citationSuffix  = []
+                        , citationMode    = AuthorInText
+                        , citationNoteNum = 0
+                        , citationHash    = 0
+                        }
+                ] "@item1")
+          , "key starts with digit" =:
+            "@1657:huyghens" =?> para (cite [
+                Citation{ citationId      = "1657:huyghens"
+                        , citationPrefix  = []
+                        , citationSuffix  = []
+                        , citationMode    = AuthorInText
+                        , citationNoteNum = 0
+                        , citationHash    = 0
+                        }
+                ] "@1657:huyghens")
+          ]
         ]