Support CDDL dfns, extract standard prelude from CDDL RFC (#1750)

New types of definitions will soon be introduced in Bikeshed to deal with
CDDL blocks: cddl-module, cddl-type, cddl-parameter, cddl-key, cddl-value. The
extraction now considers that these definition types are valid.

To be able to reference CDDL types defined in the standard prelude, a
pre-processing step is also added for the CDDL RFC (RFC8610). To avoid creating
multiple definitions with the same ID and href, which could perhaps confuse
consuming tools (?), all types defined in the standard prelude get attached as
different linking text to the same cddl-type dfn.

src/browserlib/extract-dfns.mjs

@@ -85,6 +85,12 @@ function hasValidType(el) {
     'element-attr',
     'attr-value',
 
+    // CDDL types
+    'cddl-module',
+    'cddl-type',
+    'cddl-parameter',
+    'cddl-key',
+    'cddl-value',
 
     // URL scheme
     'scheme',
@@ -231,13 +237,15 @@ function definitionMapper(el, idToHeading, usesDfnDataModel) {
       [],
 
     // Definition is public if explicitly marked as exportable or if export has
-    // not been explicitly disallowed and its type is not "dfn", or if the spec
-    // is an old spec that does not use the "data-dfn-type" convention.
+    // not been explicitly disallowed and its type is not "dfn" or a CDDL type,
+    // or if the spec is an old spec that does not use the "data-dfn-type"
+    // convention.
     access: (!usesDfnDataModel ||
              el.hasAttribute('data-export') ||
              (!el.hasAttribute('data-noexport') &&
               el.hasAttribute('data-dfn-type') &&
-              el.getAttribute('data-dfn-type') !== 'dfn')) ?
+              el.getAttribute('data-dfn-type') !== 'dfn' &&
+              !el.getAttribute('data-dfn-type').startsWith('cddl-'))) ?
       'public' : 'private',
 
     // Whether the term is defined in a normative/informative section
@@ -293,6 +301,10 @@ export default function (spec, idToHeading = {}) {
   case "SVG2":
     preProcessSVG2();
     break;
+  case "rfc8610":
+    // RFC8610 defines CDDL
+    preProcessRFC8610();
+    break;
   }
 
   const definitions = [...document.querySelectorAll(definitionsSelector)];
@@ -861,3 +873,53 @@ function preProcessSVG2() {
   });
 
 }
+
+/**
+ * The CDDL RFC defines a standard prelude with a number of CDDL types that
+ * other specs that define CDDL make extensive use of. To be able to link back
+ * to these type definitions from other specs, we need these types to appear
+ * in the dfns extract of the RFC somehow.
+ *
+ * Now, the RFC only defines one ID for the appendix that contains the
+ * standard prelude. We need to "share" that ID across all types. To avoid
+ * introducing definitions that have the same ID and href, which could perhaps
+ * confuse tools that ingest the definitions, the approach taken here is to
+ * create a single definition that contains all the types as linking text.
+ */
+function preProcessRFC8610() {
+  // The RFC is defined as a set of pages (yuck!)
+  // The standard prelude is an appendix, let's look for it
+  const prePages = [...document.querySelectorAll('pre.newpage')];
+  const preludeStart = /<a [^>]*id=[^>]*>Appendix .<\/a>\.\s+Standard Prelude/;
+  const preludeEnd = /Figure \d+: CDDL Prelude/;
+  const preStart = prePages
+    .findIndex(pre => pre.innerHTML.match(preludeStart));
+  if (preStart === -1) {
+    // Can't find the expected prelude start text, not a good start!
+    return;
+  }
+  const preEnd = prePages
+    .findIndex((pre, idx) => idx >= preStart && pre.innerHTML.match(preludeEnd));
+  if (preEnd === -1) {
+    // Can't find the expected prelude ending text, not a good start!
+    return;
+  }
+
+  // Extract the list of types defined in the appendix
+  const preludeTypes = prePages.slice(preStart, preEnd + 1)
+    .map(pre => [...pre.innerHTML.matchAll(/^\s+([a-z0-9\-]+) = .*$/mg)]
+      .map(m => m[1])
+    )
+    .flat();
+
+  // Convert the appendix heading into a cddl-type definition that lists
+  // all CDDL types.
+  const el = prePages[preStart].querySelector(`a[id]`);
+  const dfn = document.createElement("dfn");
+  dfn.id = el.id;
+  dfn.dataset.dfnType = 'cddl-type';
+  dfn.dataset.lt = preludeTypes.join('|');
+  dfn.dataset.export = '';
+  dfn.textContent = el.textContent;
+  el.replaceWith(dfn);
+}