Move instructions from script to readme. Skip ppp extension as it rem…

…oves fields.

README.md

@@ -158,6 +158,20 @@ You can now generate a table for each form, displaying, for each element and att
  for i in 01 02 03 04 05 06 07 08 12 13 14 15 20 21 22 23 24 25; rake table LANGUAGE=EN FILES=F$i > path/to/european-union/docs/F$i.md; end
  for i in 01 02; rake table LANGUAGE=EN FILES=MOVE FORM=T$i > path/to/european-union/docs/T$i.md; end
 
+### Find fields for which to write extensions
+
+Generate a release schema with all extensions applied, except the PPP extension (which removes fields):
+
+ python scripts/patched_release_schema.py > scripts/release-schema-patched.json
+
+Generate a CSV file with all fields from the extended schema, including a column for the extension name:
+
+ ocdskit mapping-sheet --infer-required --extension-field extension scripts/release-schema-patched.json > scripts/mapping-sheet.csv
+
+Print a list of fields for which there are no extensions:
+
+ python scripts/mapped_ocds_fields.py
+
 ## Design
 
 * Label keys are expected to change less frequently than labels. The code therefore focuses on label keys.

scripts/patched_release_schema.py

@@ -1,8 +1,3 @@
-"""
-python scripts/patched_release_schema.py > scripts/release-schema-patched.json
-ocdskit mapping-sheet --infer-required --extension-field extension release-schema-patched.json > scripts/mapping-sheet.csv
-"""
-
 import json
 import sys
 
@@ -13,9 +8,12 @@
 
 url = 'https://raw.githubusercontent.com/open-contracting/extension_registry/master/extension_versions.csv'
 for version in ExtensionRegistry(url):
+ if version.id == 'ppp': # PPP extension deletes core fields
+ continue
  if version.id not in extensions:
  extensions[version.id] = []
  extensions[version.id].append(version)
+
 urls = [get_latest_version(versions).download_url for versions in extensions.values()]
 
 # TODO: Uncomment extensions once PRs merged.