1 files changed, 99 insertions, 0 deletions
diff --git a/doc/neps/tools/build_index.py b/doc/neps/tools/build_index.py
new file mode 100644
index 000000000..65225c995
--- /dev/null
+++ b/doc/neps/tools/build_index.py
@@ -0,0 +1,99 @@
+"""
+Scan the directory of nep files and extract their metadata.  The
+metadata is passed to Jinja for filling out `index.rst.tmpl`.
+"""
+
+import os
+import sys
+import jinja2
+import glob
+import re
+
+
+def render(tpl_path, context):
+    path, filename = os.path.split(tpl_path)
+    return jinja2.Environment(
+        loader=jinja2.FileSystemLoader(path or './')
+    ).get_template(filename).render(context)
+
+def nep_metadata():
+    ignore = ('nep-template.rst')
+    sources = sorted(glob.glob(r'nep-*.rst'))
+    sources = [s for s in sources if not s in ignore]
+
+    meta_re = r':([a-zA-Z\-]*): (.*)'
+
+    neps = {}
+    print('Loading metadata for:')
+    for source in sources:
+        print(f' - {source}')
+        nr = int(re.match(r'nep-([0-9]{4}).*\.rst', source).group(1))
+
+        with open(source) as f:
+            lines = f.readlines()
+            tags = [re.match(meta_re, line) for line in lines]
+            tags = [match.groups() for match in tags if match is not None]
+            tags = {tag[0]: tag[1] for tag in tags}
+
+            # We could do a clever regexp, but for now just assume the title is
+            # the second line of the document
+            tags['Title'] = lines[1].strip()
+            tags['Filename'] = source
+
+
+        if tags['Status'] in ('Accepted', 'Rejected', 'Withdrawn'):
+            if not 'Resolution' in tags:
+                raise RuntimeError(
+                    f'NEP {nr} is Accepted/Rejected/Withdrawn but '
+                    'has no Resolution tag'
+                )
+
+        neps[nr] = tags
+
+    # Now that we have all of the NEP metadata, do some global consistency
+    # checks
+
+    for nr, tags in neps.items():
+        if tags['Status'] == 'Superseded':
+            if not 'Replaced-By' in tags:
+                raise RuntimeError(
+                    f'NEP {nr} has been Superseded, but has no Replaced-By tag'
+                )
+
+            replaced_by = int(tags['Replaced-By'])
+            replacement_nep = neps[replaced_by]
+
+            if not 'Replaces' in replacement_nep:
+                raise RuntimeError(
+                    f'NEP {nr} is superseded by {replaced_by}, but that NEP has '
+                    f"no Replaces tag."
+                )
+
+            if not int(replacement_nep['Replaces']) == nr:
+                raise RuntimeError(
+                    f'NEP {nr} is superseded by {replaced_by}, but that NEP has a '
+                    f"Replaces tag of `{replacement_nep['Replaces']}`."
+                )
+
+        if 'Replaces' in tags:
+            replaced_nep = int(tags['Replaces'])
+            replaced_nep_tags = neps[replaced_nep]
+            if not replaced_nep_tags['Status'] == 'Superseded':
+                raise RuntimeError(
+                    f'NEP {nr} replaces {replaced_nep}, but that NEP has not '
+                    f'been set to Superseded'
+                )
+
+    return {'neps': neps}
+
+
+infile = 'index.rst.tmpl'
+outfile = 'index.rst'
+
+meta = nep_metadata()
+
+print(f'Compiling {infile} -> {outfile}')
+index = render(infile, meta)
+
+with open(outfile, 'w') as f:
+    f.write(index)