Fix #9507 Describe accurately acceptable package names

doc/buildinfo-fields-reference.rst

@@ -12,7 +12,7 @@ Field syntax is described as they are in the latest cabal file format version.
 
   .. math::
 
-      \mathord{"}\mathtt{example}\mathord{"}
+      \mathord{``}\mathtt{example}\mathord{"}
 
 * non-terminals are type set in italic:
 
@@ -25,13 +25,13 @@ Field syntax is described as they are in the latest cabal file format version.
 
   .. math::
 
-      [ \mathord{"}\mathtt{1}\mathord{"} \cdots \mathord{"}\mathtt{9}\mathord{"} ]
+      [ \mathord{``}\mathtt{1}\mathord{"} \cdots \mathord{``}\mathtt{9}\mathord{"} ]
 
   Character set complements have :math:`c` superscript:
 
   .. math::
 
-      [ \mathord{"}\mathtt{1}\mathord{"} \cdots \mathord{"}\mathtt{9}\mathord{"} ]^c
+      [ \mathord{``}\mathtt{1}\mathord{"} \cdots \mathord{``}\mathtt{9}\mathord{"} ]^c
 
 * repetition is type set using regular expression inspired notation.
   Superscripts tell how many time to repeat:
@@ -134,10 +134,13 @@ hs-string
         \mathop{\mathord{``}\mathtt{\text{"}}\mathord{"}}{\left\{ {[\mathop{\mathord{``}\mathtt{\text{"}}\mathord{"}}\mathop{\mathord{``}\mathtt{\text{\\}}\mathord{"}}]^c}\mid\left\{ \begin{gathered}\mathop{\mathord{``}\mathtt{\text{\\}\text{&}}\mathord{"}}\\\mathop{\mathord{``}\mathtt{\text{\\}\text{\\}}\mathord{"}}\\\left\{ \mathop{\mathord{``}\mathtt{\text{\\}n}\mathord{"}}\mid\mathop{\mathit{escapes}} \right\}\\\mathop{\mathord{``}\mathtt{\text{\\}}\mathord{"}}[\mathop{\mathord{``}\mathtt{0}\mathord{"}}\cdots\mathop{\mathord{``}\mathtt{9}\mathord{"}}]\\\mathop{\mathord{``}\mathtt{\text{\\}o}\mathord{"}}[\mathop{\mathord{``}\mathtt{0}\mathord{"}}\cdots\mathop{\mathord{``}\mathtt{7}\mathord{"}}]\\\mathop{\mathord{``}\mathtt{\text{\\}x}\mathord{"}}[\mathop{\mathord{``}\mathtt{0}\mathord{"}}\cdots\mathop{\mathord{``}\mathtt{9}\mathord{"}}\mathop{\mathord{``}\mathtt{A}\mathord{"}}\cdots\mathop{\mathord{``}\mathtt{F}\mathord{"}}\mathop{\mathord{``}\mathtt{a}\mathord{"}}\cdots\mathop{\mathord{``}\mathtt{f}\mathord{"}}]\\\left\{ \mathop{\mathord{``}\mathtt{\text{\\}\text{^}\text{@}}\mathord{"}}\mid\mathop{\mathit{control}} \right\}\\\left\{ \mathop{\mathord{``}\mathtt{\text{\\}NUL}\mathord{"}}\mid\mathop{\mathit{ascii}} \right\}\end{gathered} \right\} \right\}}^\ast_{}\mathop{\mathord{``}\mathtt{\text{"}}\mathord{"}}
 
 unqual-name
-    Unqualified component names are used for package names, component names etc. but not flag names. Unqualified component name consist of components separated by dash, each component is non-empty alphanumeric string, with at least one alphabetic character. In other words, component may not look like a number.
+    Unqualified component names are used for package names, component names etc. but not flag names. An unqualified component name consists of components separated by a hyphen, each component is a non-empty alphanumeric string, with at least one character that is not the digits ``0`` to ``9``. In other words, a component may not look like a number.
 
     .. math::
-        {\left({\mathop{\mathit{alpha\text{-}num}}}^\ast_{}\mathop{\mathit{alpha}}{\mathop{\mathit{alpha\text{-}num}}}^\ast_{}\right)}^+_{\mathop{\mathord{``}\mathtt{\text{-}}\mathord{"}}}
+        {\left({\mathop{\mathit{alpha\text{-}num}}}^\ast_{}{\mathop{\mathit{alpha\text{-}num\text{-}not\text{-}digit}}}\:{\mathop{\mathit{alpha\text{-}num}}}^\ast_{}\right)}^+_{\mathop{\mathord{``}\mathtt{\text{-}}\mathord{"}}}
+
+    .. math::
+        {\mathop{\mathit{alpha\text{-}num\text{-}not\text{-}digit}}} = {\mathop{\mathit{alpha\text{-}num}}}\cap{[ \mathord{``}\mathtt{0}\mathord{"} \cdots \mathord{``}\mathtt{9}\mathord{"} ]^c}
 
 module-name
     Haskell module name as recognized by Cabal parser.

doc/cabal-package-description-file.rst

@@ -318,24 +318,39 @@ describe the package as a whole:
     tools require the package-name specified for this field to match
     the package description's file-name :file:`{package-name}.cabal`.
 
-    Package names are case-sensitive and must match the regular expression
-    (i.e. alphanumeric "words" separated by dashes; each alphanumeric
-    word must contain at least one letter):
-    ``[[:digit:]]*[[:alpha:]][[:alnum:]]*(-[[:digit:]]*[[:alpha:]][[:alnum:]]*)*``.
+    A valid package name comprises an alphanumeric 'word'; or two or more
+    such words separated by a hyphen character (``-``). A word cannot be
+    comprised only of the digits ``0`` to ``9``.
 
-    Or, expressed in ABNF_:
+    An alphanumeric character belongs to one of the Unicode Letter categories
+    (Lu (uppercase), Ll (lowercase), Lt (titlecase), Lm (modifier), or
+    Lo (other)) or Number categories (Nd (decimal), Nl (letter), or No (other)).
+
+    Package names are case-sensitive.
+
+    Expressed as a regular expression:
+
+    ``[0-9]*[\p{L}\p{N}-[0-9]][\p{L}\p{N}]*(-[0-9]*[\p{L}\p{N}-[0-9]][\p{L}\p{N}]*)*``
+
+    Expressed in ABNF_:
 
     .. code-block:: abnf
 
         package-name      = package-name-part *("-" package-name-part)
-        package-name-part = *DIGIT UALPHA *UALNUM
+        package-name-part = *DIGIT UALPHANUM-NOT-DIGIT *UALNUM
 
-        UALNUM = UALPHA / DIGIT
-        UALPHA = ... ; set of alphabetic Unicode code-points
+        DIGIT = %x30-39 ; 0-9
+
+        UALNUM = UALPHANUM-NOT-DIGIT / DIGIT
+        UALPHANUM-NOT-DIGIT = ... ; set of Unicode code-points in Letter or
+                                  ; Number categories, other than the DIGIT
+                                  ; code-points
 
     .. note::
 
-        Hackage restricts package names to the ASCII subset.
+        Hackage will not accept package names that use alphanumeric characters
+        other than ``A`` to ``Z``, ``a`` to ``z``, and ``0`` to ``9``
+        (the ASCII subset).
 
 .. pkg-field:: version: numbers (required)
 
@@ -1480,13 +1495,13 @@ system-dependent values for these fields.
     Version constraints use the operators ``==, >=, >, <, <=`` and a
     version number. Multiple constraints can be combined using ``&&`` or
     ``||``.
-    
+
     .. Note::
 
        Even though there is no ``/=`` operator, by combining operators we can
        skip over one or more versions, to skip a deprecated version or to skip
        versions that narrow the constraint solving more than we'd like.
-       
+
        For example, the ``time =1.12.*`` series depends on ``base >=4.13 && <5``
        but ``time-1.12.3`` bumps the lower bound on base to ``>=4.14``.  If we
        still want to compile with a ``ghc-8.8.*`` version of GHC that ships with

doc/package-concepts.rst

@@ -43,7 +43,7 @@ Package names and versions
 All packages have a name, e.g. "HUnit". Package names are assumed to be
 unique. Cabal package names may contain letters, numbers and hyphens,
 but not spaces and may also not contain a hyphened section consisting of
-only numbers. The namespace for Cabal packages is flat, not
+only of the digits ``0`` to ``9``. The namespace for Cabal packages is flat, not
 hierarchical.
 
 Packages also have a version, e.g "1.1". This matches the typical way in