netcdf-c/nczarr_test/ref_jsonconvention.cdl
Dennis Heimbigner 9f78be8bb8 Allow the read/write of JSON-valued Zarr attributes.
A number of other packages that read/write Zarr insert
attributes whose value is a dictionary containing specialized
information.  An example is the GDAL Driver convention (see
https://gdal.org/drivers/raster/zarr.html).

In order to handle such attributes, this PR enforces a special
convention. It applies to both pure Zarr an NCZarr format as
written by the netdf-c library.

The convention is as follows:

## Reading
Suppose an attribute is read from *.zattrs* and it has a JSON
value that is a a dictionary.  In this case, the JSON dictionary
is converted to a string value.  It then appears in the netcdf-c
API as if it is a character valued attribute of the same name,
and whose value is the "stringified" dictionary.

# Writing
Suppose an attribute is of type character and its *value* *looks like*
a JSON dictionary. In this case, it is parsed to JSON
and written as the value of the attribute in the NCZarr file.
Here the *value* is the concatenation of all the characters
in the attributes netcdf-c value.
The term "looks like" means that the *value*'s first character is
"{", its last value is "}", and it can be successfully parsed
by a JSON parser.

A test case, *nczarr_test/run_jsonconventions.sh* was also added.

## Misc. Unrelated Changes

1. Fix an error in nc_test4/tst_broken_files.c
2. Modify the internal JSON parser API.
3. Modify the nczarr_test/zisjson program is modified to support
   this convention.
2022-04-06 18:22:59 -06:00

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netcdf tmp_jsonconvention {
dimensions:
d1 = 1 ;
variables:
int v(d1) ;
v:varconvention = "{\n\"key1\": [1,2,3], \"key2\": {\"key3\": \"abc\"}}" ;
// global attributes:
:grpconvention = "{\"key1\": [1,2,3], \n\"key2\": {\"key3\": \"abc\"}}" ;
data:
v = _ ;
}