Markdown below:
Bug report: Incorrect json representation for graphics.
## Extended description
The json representation for graphics (which I believe is intended for
Jmol),
is **not** correct json. To wit:
sage: G = cube((0,0,0),1)
sage: obj_list =
sage.plot.plot3d.base.flatten_list(G.flatten().json_repr(G.default_render_params()))
sage: j = obj_list[0]
sage: print j # json
{vertices:[{x:0.5,y:0.5,z:0.5},{x:-0.5,y:0.5,z:0.5},{x:-0.5,y:-0.5,z:0.5},{x:0.5,y:-0.5,z:0.5},{x:0.5,y:0.5,z:-0.5},{x:-0.5,y:0.5,z:-0.5},{x:0.5,y:-0.5,z:-0.5},{x:-0.5,y:-0.5,z:-0.5}],faces:[[0,1,2,3],[0,4,5,1],[0,3,6,4],[5,4,6,7],[6,3,2,7],[2,1,5,7]],color:'#6666ff'}
sage: import json
sage: json.loads(j) # Throws value error
## Sage Version:
sage: version()
'SageMath Version 7.1, Release Date: 2016-03-20'
## Operating System:
macOS Sierra Version 10.12.2
The bug is reproducible in other OSs, though.
## Solution
I've traced down the problem, but I don't know if I should submit a pull
request on Github
or what. Advice on what to do is welcome.
The problem lies in the file `src/sage/plot/plot3d/index_face_set.pyx`,
where the json is generated. There are two problems with the generated json:
1. The quote signs used in the file are `'` and not `"` as per [Json
spec](http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf).
2. Every dictionary key is unquoted, which is incorrect. Thus, a point
{x:0,y:0,z:0}
should really be
{"x":0,"y":0,"z":0}
as per Json spec.
In particular, the function `cdef inline format_json_vertex(point_c P):`
should read:
cdef inline format_json_vertex(point_c P):
cdef char ss[100]
cdef Py_ssize_t r = sprintf_3d(ss, '{"x":%g,"y":%g,"z":%g}', P.x,
P.y, P.z)
return PyString_FromStringAndSize(ss, r)
and lines 871 through 882 should read:
if self.global_texture:
color_str = '"#{}"'.format(self.texture.hex_rgb())
return ['{"vertices":%s,"faces":%s,"color":%s}' %
(vertices_str, faces_str, color_str)]
else:
color_str = "[{}]".format(",".join(['"{}"'.format(
Color(self._faces[i].color.r,
self._faces[i].color.g,
self._faces[i].color.b).html_color())
for i from 0 <= i <
self.fcount]))
return ['{"vertices":%s,"faces":%s,"face_colors":%s}' %
(vertices_str, faces_str, color_str)]
This will affect doctest output, btw.
## Workaround for existing installations:
The silver lining is that even though the Json is incorrect, since it is
very simple, it can be easly corrected inline:
import re
def correct_json(s):
"""
Correct the json returned by `Graphics3d.json_repr()`, which
contains the following
errors:
1. it uses ' instead of " for strings.
2. dictionary keys are not quoted.
"""
j = re.sub(r"{\s*(\w+)\s*:\s*", r'{"\1":', s)
j = re.sub(r",\s*(\w+)\s*:\s*", r',"\1":', j)
j = re.sub(r"'", r'"', j)
return j
Note that this `correct_json` does **not** work for general json, just for
the particularly simple json produced by the graphics3d module.
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