qapi: add qapi2texi script

As the name suggests, the qapi2texi script converts JSON QAPI
description into a texi file suitable for different target
formats (info/man/txt/pdf/html...).

It parses the following kind of blocks:

Free-form:

  ##
  # = Section
  # == Subsection
  #
  # Some text foo with *emphasis*
  # 1. with a list
  # 2. like that
  #
  # And some code:
  # | $ echo foo
  # | -> do this
  # | <- get that
  #
  ##

Symbol description:

  ##
  # @symbol:
  #
  # Symbol body ditto ergo sum. Foo bar
  # baz ding.
  #
  # @param1: the frob to frobnicate
  # @param2: #optional how hard to frobnicate
  #
  # Returns: the frobnicated frob.
  #          If frob isn't frobnicatable, GenericError.
  #
  # Since: version
  # Notes: notes, comments can have
  #        - itemized list
  #        - like this
  #
  # Example:
  #
  # -> { "execute": "quit" }
  # <- { "return": {} }
  #
  ##

That's roughly following the following EBNF grammar:

api_comment = "##\n" comment "##\n"
comment = freeform_comment | symbol_comment
freeform_comment = { "# " text "\n" | "#\n" }
symbol_comment = "# @" name ":\n" { member | tag_section | freeform_comment }
member = "# @" name ':' [ text ] "\n" freeform_comment
tag_section = "# " ( "Returns:", "Since:", "Note:", "Notes:", "Example:", "Examples:" ) [ text ]  "\n" freeform_comment
text = free text with markup

Note that the grammar is ambiguous: a line "# @foo:\n" can be parsed
both as freeform_comment and as symbol_comment.  The actual parser
recognizes symbol_comment.

See docs/qapi-code-gen.txt for more details.

Deficiencies and limitations:
- the generated QMP documentation includes internal types
- union type support is lacking
- type information is lacking in generated documentation
- doc comment error message positions are imprecise, they point
  to the beginning of the comment.
- a few minor issues, all marked TODO/FIXME in the code

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170113144135.5150-16-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[test-qapi.py tweaked to avoid trailing empty lines in .out]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 271 insertions, 0 deletions

diff --git a/scripts/qapi2texi.py b/scripts/qapi2texi.py
new file mode 100755
index 0000000000..83ded95c2d
--- /dev/null
+++ b/scripts/qapi2texi.py
@@ -0,0 +1,271 @@
+#!/usr/bin/env python
+# QAPI texi generator
+#
+# This work is licensed under the terms of the GNU LGPL, version 2+.
+# See the COPYING file in the top-level directory.
+"""This script produces the documentation of a qapi schema in texinfo format"""
+import re
+import sys
+
+import qapi
+
+COMMAND_FMT = """
+@deftypefn {type} {{}} {name}
+
+{body}
+
+@end deftypefn
+
+""".format
+
+ENUM_FMT = """
+@deftp Enum {name}
+
+{body}
+
+@end deftp
+
+""".format
+
+STRUCT_FMT = """
+@deftp {{{type}}} {name}
+
+{body}
+
+@end deftp
+
+""".format
+
+EXAMPLE_FMT = """@example
+{code}
+@end example
+""".format
+
+
+def subst_strong(doc):
+    """Replaces *foo* by @strong{foo}"""
+    return re.sub(r'\*([^*\n]+)\*', r'@emph{\1}', doc)
+
+
+def subst_emph(doc):
+    """Replaces _foo_ by @emph{foo}"""
+    return re.sub(r'\b_([^_\n]+)_\b', r' @emph{\1} ', doc)
+
+
+def subst_vars(doc):
+    """Replaces @var by @code{var}"""
+    return re.sub(r'@([\w-]+)', r'@code{\1}', doc)
+
+
+def subst_braces(doc):
+    """Replaces {} with @{ @}"""
+    return doc.replace("{", "@{").replace("}", "@}")
+
+
+def texi_example(doc):
+    """Format @example"""
+    # TODO: Neglects to escape @ characters.
+    # We should probably escape them in subst_braces(), and rename the
+    # function to subst_special() or subs_texi_special().  If we do that, we
+    # need to delay it until after subst_vars() in texi_format().
+    doc = subst_braces(doc).strip('\n')
+    return EXAMPLE_FMT(code=doc)
+
+
+def texi_format(doc):
+    """
+    Format documentation
+
+    Lines starting with:
+    - |: generates an @example
+    - =: generates @section
+    - ==: generates @subsection
+    - 1. or 1): generates an @enumerate @item
+    - */-: generates an @itemize list
+    """
+    lines = []
+    doc = subst_braces(doc)
+    doc = subst_vars(doc)
+    doc = subst_emph(doc)
+    doc = subst_strong(doc)
+    inlist = ""
+    lastempty = False
+    for line in doc.split('\n'):
+        empty = line == ""
+
+        # FIXME: Doing this in a single if / elif chain is
+        # problematic.  For instance, a line without markup terminates
+        # a list if it follows a blank line (reaches the final elif),
+        # but a line with some *other* markup, such as a = title
+        # doesn't.
+        #
+        # Make sure to update section "Documentation markup" in
+        # docs/qapi-code-gen.txt when fixing this.
+        if line.startswith("| "):
+            line = EXAMPLE_FMT(code=line[2:])
+        elif line.startswith("= "):
+            line = "@section " + line[2:]
+        elif line.startswith("== "):
+            line = "@subsection " + line[3:]
+        elif re.match(r'^([0-9]*\.) ', line):
+            if not inlist:
+                lines.append("@enumerate")
+                inlist = "enumerate"
+            line = line[line.find(" ")+1:]
+            lines.append("@item")
+        elif re.match(r'^[*-] ', line):
+            if not inlist:
+                lines.append("@itemize %s" % {'*': "@bullet",
+                                              '-': "@minus"}[line[0]])
+                inlist = "itemize"
+            lines.append("@item")
+            line = line[2:]
+        elif lastempty and inlist:
+            lines.append("@end %s\n" % inlist)
+            inlist = ""
+
+        lastempty = empty
+        lines.append(line)
+
+    if inlist:
+        lines.append("@end %s\n" % inlist)
+    return "\n".join(lines)
+
+
+def texi_body(doc):
+    """
+    Format the body of a symbol documentation:
+    - main body
+    - table of arguments
+    - followed by "Returns/Notes/Since/Example" sections
+    """
+    body = texi_format(str(doc.body)) + "\n"
+    if doc.args:
+        body += "@table @asis\n"
+        for arg, section in doc.args.iteritems():
+            desc = str(section)
+            opt = ''
+            if "#optional" in desc:
+                desc = desc.replace("#optional", "")
+                opt = ' (optional)'
+            body += "@item @code{'%s'}%s\n%s\n" % (arg, opt,
+                                                   texi_format(desc))
+        body += "@end table\n"
+
+    for section in doc.sections:
+        name, doc = (section.name, str(section))
+        func = texi_format
+        if name.startswith("Example"):
+            func = texi_example
+
+        if name:
+            # FIXME the indentation produced by @quotation in .txt and
+            # .html output is confusing
+            body += "\n@quotation %s\n%s\n@end quotation" % \
+                    (name, func(doc))
+        else:
+            body += func(doc)
+
+    return body
+
+
+def texi_alternate(expr, doc):
+    """Format an alternate to texi"""
+    body = texi_body(doc)
+    return STRUCT_FMT(type="Alternate",
+                      name=doc.symbol,
+                      body=body)
+
+
+def texi_union(expr, doc):
+    """Format a union to texi"""
+    discriminator = expr.get("discriminator")
+    if discriminator:
+        union = "Flat Union"
+    else:
+        union = "Simple Union"
+
+    body = texi_body(doc)
+    return STRUCT_FMT(type=union,
+                      name=doc.symbol,
+                      body=body)
+
+
+def texi_enum(expr, doc):
+    """Format an enum to texi"""
+    for i in expr['data']:
+        if i not in doc.args:
+            doc.args[i] = ''
+    body = texi_body(doc)
+    return ENUM_FMT(name=doc.symbol,
+                    body=body)
+
+
+def texi_struct(expr, doc):
+    """Format a struct to texi"""
+    body = texi_body(doc)
+    return STRUCT_FMT(type="Struct",
+                      name=doc.symbol,
+                      body=body)
+
+
+def texi_command(expr, doc):
+    """Format a command to texi"""
+    body = texi_body(doc)
+    return COMMAND_FMT(type="Command",
+                       name=doc.symbol,
+                       body=body)
+
+
+def texi_event(expr, doc):
+    """Format an event to texi"""
+    body = texi_body(doc)
+    return COMMAND_FMT(type="Event",
+                       name=doc.symbol,
+                       body=body)
+
+
+def texi_expr(expr, doc):
+    """Format an expr to texi"""
+    (kind, _) = expr.items()[0]
+
+    fmt = {"command": texi_command,
+           "struct": texi_struct,
+           "enum": texi_enum,
+           "union": texi_union,
+           "alternate": texi_alternate,
+           "event": texi_event}[kind]
+
+    return fmt(expr, doc)
+
+
+def texi(docs):
+    """Convert QAPI schema expressions to texi documentation"""
+    res = []
+    for doc in docs:
+        expr = doc.expr
+        if not expr:
+            res.append(texi_body(doc))
+            continue
+        try:
+            doc = texi_expr(expr, doc)
+            res.append(doc)
+        except:
+            print >>sys.stderr, "error at @%s" % doc.info
+            raise
+
+    return '\n'.join(res)
+
+
+def main(argv):
+    """Takes schema argument, prints result to stdout"""
+    if len(argv) != 2:
+        print >>sys.stderr, "%s: need exactly 1 argument: SCHEMA" % argv[0]
+        sys.exit(1)
+
+    schema = qapi.QAPISchema(argv[1])
+    print texi(schema.docs)
+
+
+if __name__ == "__main__":
+    main(sys.argv)