parser.py: add an option to keep only certain fields

Keeping only some fields is handy to generate summaries for triaging.

This does not apply to the markdown and config template formats, which
depend on certain fields being present.
Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>

README.md

@@ -65,6 +65,19 @@ $ ./parser.py \
                 or True" ...
 ```
 
+### Keeping only certain fields
+
+Except for the markdown and the config template formats, it is possible to
+specify which tests data fields to actually write using the `--fields` option.
+
+Example command, suitable for triaging:
+
+``` {.sh}
+$ ./parser.py --fields 'result,sub set,descr,name,log' ...
+```
+
+The csv format can retain the fields order.
+
 ## Configuration file
 
 It is possible to use a configuration file with command line option `--config

parser.py

@@ -349,20 +349,49 @@ def sort_data(cross_check, sort_keys):
         cross_check.sort(key=lambda x: x[k])
 
 
-# Generate csv
-def gen_csv(cross_check, filename):
-    # Find keys
-    keys = set()
+# Keep only certain fields in data, in-place
+# The fields to write are supplied as a comma-separated list
+def keep_fields(cross_check, fields):
+    logging.debug(f"Keeping fields: `{fields}'")
+    s = set(fields.split(','))
 
     for x in cross_check:
-        keys = keys.union(x.keys())
+        for k in list(x.keys()):
+            if k not in s:
+                del x[k]
+
+
+# Discover fields
+# The fields can be supplied as a comma-separated list
+# Order is preserved
+# Additional fields are auto-discovered and added to the list, sorted
+def discover_fields(cross_check, fields=None):
+    if fields is not None:
+        keys = fields.split(',')
+    else:
+        keys = []
+
+    # Find keys, not already listed
+    s = set()
 
-    # Write csv
-    logging.debug(f'Generate {filename}')
+    for x in cross_check:
+        s = s.union(x.keys())
+
+    s = s.difference(keys)
+    keys += sorted(s)
+
+    logging.debug(f'Fields: {keys}')
+    return keys
+
+
+# Generate csv
+# The fields to write are supplied as a list
+def gen_csv(cross_check, filename, fields):
+    logging.debug(f'Generate {filename} (fields: {fields})')
 
     with open(filename, 'w', newline='') as csvfile:
         writer = csv.DictWriter(
-            csvfile, fieldnames=sorted(keys), delimiter=';')
+            csvfile, fieldnames=fields, delimiter=';')
         writer.writeheader()
         writer.writerows(cross_check)
 
@@ -511,6 +540,8 @@ def main():
     parser.add_argument(
         '--sort', help='Comma-separated list of keys to sort output on')
     parser.add_argument('--filter', help='Python expression to filter results')
+    parser.add_argument(
+        '--fields', help='Comma-separated list of fields to write')
     parser.add_argument(
         'log_file', nargs='?', default='sample.ekl',
         help='Input .ekl filename')
@@ -616,9 +647,21 @@ def main():
             key_tree_2_md(bins[k], resultfile, "group")
             n += 1
 
+    # Generate yaml config template if requested
+    if 'template' in args and args.template is not None:
+        gen_template(cross_check, args.template)
+
+    # Filter fields before writing any other type of output
+    # Do not rely on specific fields being present after this step
+    if args.fields is not None:
+        keep_fields(cross_check, args.fields)
+
+    # Auto-discover the fields and take the option into account
+    fields = discover_fields(cross_check, args.fields)
+
     # Generate csv if requested
     if args.csv is not None:
-        gen_csv(cross_check, args.csv)
+        gen_csv(cross_check, args.csv, fields)
 
     # Generate json if requested
     if args.json is not None:
@@ -628,10 +671,6 @@ def main():
     if 'yaml' in args and args.yaml is not None:
         gen_yaml(cross_check, args.yaml)
 
-    # Generate yaml config template if requested
-    if 'template' in args and args.template is not None:
-        gen_template(cross_check, args.template)
-
     # command line argument 3&4, key are to support a key & value search.
     # these will be displayed in CLI
     if args.find_key is not None and args.find_value is not None: