hgweb: always return iterable from @webcommand functions (API)

hgweb: always return iterable from @webcommand functions (API)

We had to hack up this function to support our transition to the
new response API. Now that we're done with the transition (!!),
we can return to returning an iterator of content chunks from
these functions.

It is tempting to return a normal object and not a generator.
However, as the keyword extension demonstrates, extensions may
wish to wrap commands and have a try..finally block around
execution. Since there is a generator producing content and
that generator could be executing code, the try..finally needs
to live for as long as the generator is running. That means we
have to return a generator so wrappers can consume the generator
inside a try..finally.

.. api::

   hgweb @webcommand functions must use the new response object
   passed in via ``web.res`` to initiate sending of a response.
   The hgweb WSGI application will no longer start sending the
   response automatically.

Differential Revision: https://phab.mercurial-scm.org/D2796

--- a/hgext/highlight/__init__.py	Sat Mar 10 18:51:32 2018 -0800
+++ b/hgext/highlight/__init__.py	Sat Mar 10 20:35:35 2018 -0800
@@ -88,7 +88,7 @@
         '/* pygments_style = %s */\n\n' % pg_style,
         fmter.get_style_defs(''),
     ]))
-    return web.res
+    return web.res.sendresponse()
 
 def extsetup():
     # monkeypatch in the new version

--- a/hgext/keyword.py	Sat Mar 10 18:51:32 2018 -0800
+++ b/hgext/keyword.py	Sat Mar 10 20:35:35 2018 -0800
@@ -621,13 +621,7 @@
         origmatch = kwt.match
         kwt.match = util.never
     try:
-        res = orig(web, req, tmpl)
-        if res is web.res:
-            res = res.sendresponse()
-        elif res is True:
-            return
-
-        for chunk in res:
+        for chunk in orig(web, req, tmpl):
             yield chunk
     finally:
         if kwt:

--- a/mercurial/hgweb/hgweb_mod.py	Sat Mar 10 18:51:32 2018 -0800
+++ b/mercurial/hgweb/hgweb_mod.py	Sat Mar 10 20:35:35 2018 -0800
@@ -14,7 +14,6 @@
 from .common import (
     ErrorResponse,
     HTTP_BAD_REQUEST,
-    HTTP_OK,
     cspvalues,
     permhooks,
     statusmessage,
@@ -405,15 +404,7 @@
                 # override easily enough.
                 res.status = '200 Script output follows'
                 res.headers['Content-Type'] = ctype
-                content = getattr(webcommands, cmd)(rctx, wsgireq, tmpl)
-
-                if content is res:
-                    return res.sendresponse()
-                elif content is True:
-                    return []
-                else:
-                    wsgireq.respond(HTTP_OK, ctype)
-                    return content
+                return getattr(webcommands, cmd)(rctx, wsgireq, tmpl)
 
         except (error.LookupError, error.RepoLookupError) as err:
             msg = pycompat.bytestr(err)

--- a/mercurial/hgweb/webcommands.py	Sat Mar 10 18:51:32 2018 -0800
+++ b/mercurial/hgweb/webcommands.py	Sat Mar 10 20:35:35 2018 -0800
@@ -57,12 +57,9 @@
     The functions should populate the ``rctx.res`` object with details
     about the HTTP response.
 
-    The function can return the ``requestcontext.res`` instance to signal
-    that it wants to use this object to generate the response. If an iterable
-    is returned, the ``wsgirequest`` instance will be used and the returned
-    content will constitute the response body. ``True`` can be returned to
-    indicate that the function already sent output and the caller doesn't
-    need to do anything more to send the response.
+    The function returns a generator to be consumed by the WSGI application.
+    For most commands, this should be the result from
+    ``web.res.sendresponse()``.
 
     Usage:
 
@@ -135,7 +132,7 @@
                 .replace('\\', '\\\\').replace('"', '\\"'))
     web.res.headers['Content-Disposition'] = 'inline; filename="%s"' % filename
     web.res.setbodybytes(text)
-    return web.res
+    return web.res.sendresponse()
 
 def _filerevision(web, req, tmpl, fctx):
     f = fctx.path()
@@ -165,7 +162,7 @@
         ishead=int(ishead),
         **pycompat.strkwargs(webutil.commonentry(web.repo, fctx))))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('file')
 def file(web, req, tmpl):
@@ -355,7 +352,7 @@
         showforcekw=showforcekw,
         showunforcekw=showunforcekw))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('changelog')
 def changelog(web, req, tmpl, shortlog=False):
@@ -455,7 +452,7 @@
         lessvars=lessvars,
         query=query))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('shortlog')
 def shortlog(web, req, tmpl):
@@ -490,7 +487,7 @@
     ctx = webutil.changectx(web.repo, req)
     web.res.setbodygen(tmpl('changeset',
                             **webutil.changesetentry(web, req, tmpl, ctx)))
-    return web.res
+    return web.res.sendresponse()
 
 rev = webcommand('rev')(changeset)
 
@@ -602,7 +599,7 @@
         archives=web.archivelist(hex(node)),
         **pycompat.strkwargs(webutil.commonentry(web.repo, ctx))))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('tags')
 def tags(web, req, tmpl):
@@ -638,7 +635,7 @@
         entriesnotip=lambda **x: entries(True, False, **x),
         latestentry=lambda **x: entries(True, True, **x)))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('bookmarks')
 def bookmarks(web, req, tmpl):
@@ -679,7 +676,7 @@
         entries=lambda **x: entries(latestonly=False, **x),
         latestentry=lambda **x: entries(latestonly=True, **x)))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('branches')
 def branches(web, req, tmpl):
@@ -704,7 +701,7 @@
         entries=entries,
         latestentry=latestentry))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('summary')
 def summary(web, req, tmpl):
@@ -789,7 +786,7 @@
         archives=web.archivelist('tip'),
         labels=web.configlist('web', 'labels')))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('filediff')
 def filediff(web, req, tmpl):
@@ -838,7 +835,7 @@
         diff=diffs,
         **pycompat.strkwargs(webutil.commonentry(web.repo, ctx))))
 
-    return web.res
+    return web.res.sendresponse()
 
 diff = webcommand('diff')(filediff)
 
@@ -917,7 +914,7 @@
         comparison=comparison,
         **pycompat.strkwargs(webutil.commonentry(web.repo, ctx))))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('annotate')
 def annotate(web, req, tmpl):
@@ -1011,7 +1008,7 @@
         diffopts=diffopts,
         **pycompat.strkwargs(webutil.commonentry(web.repo, fctx))))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('filelog')
 def filelog(web, req, tmpl):
@@ -1151,7 +1148,7 @@
         lessvars=lessvars,
         **pycompat.strkwargs(webutil.commonentry(web.repo, fctx))))
 
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('archive')
 def archive(web, req, tmpl):
@@ -1225,7 +1222,7 @@
                      matchfn=match,
                      subrepos=web.configbool("web", "archivesubrepos"))
 
-    return True
+    return []
 
 @webcommand('static')
 def static(web, req, tmpl):
@@ -1240,7 +1237,7 @@
         static = [os.path.join(p, 'static') for p in tp]
 
     staticfile(static, fname, web.res)
-    return web.res
+    return web.res.sendresponse()
 
 @webcommand('graph')
 def graph(web, req, tmpl):
@@ -1401,7 +1398,7 @@
         node=ctx.hex(),
         changenav=changenav))
 
-    return web.res
+    return web.res.sendresponse()
 
 def _getdoc(e):
     doc = e[0].__doc__
@@ -1463,7 +1460,7 @@
             earlycommands=earlycommands,
             othercommands=othercommands,
             title='Index'))
-        return web.res
+        return web.res.sendresponse()
 
     # Render an index of sub-topics.
     if topicname in helpmod.subtopics:
@@ -1480,7 +1477,7 @@
             topics=topics,
             title=topicname,
             subindex=True))
-        return web.res
+        return web.res.sendresponse()
 
     u = webutil.wsgiui.load()
     u.verbose = True
@@ -1506,7 +1503,7 @@
         topic=topicname,
         doc=doc))
 
-    return web.res
+    return web.res.sendresponse()
 
 # tell hggettext to extract docstrings from these functions:
 i18nfunctions = commands.values()