labels: fix labeling for non-subsystem API docs

lib/node-labels.js

@@ -117,17 +117,27 @@ function hasAllSubsystems (arr) {
   })
 }
 
+// This function is needed to help properly identify when a PR should always
+// (just) be labeled as 'doc' when it is all changes in doc/api/ that do not
+// match subsystem names (e.g. _toc.md, all.md)
+function hasAllDocChanges (arr) {
+  return arr.every((val) => {
+    return /^doc\//.test(val)
+  })
+}
+
 function matchExclusiveSubSystem (filepathsChanged) {
   const isExclusive = filepathsChanged.every(matchesAnExclusiveLabel)
   var labels = matchSubSystemsByRegex(exclusiveLabelsMap, filepathsChanged)
+
   // if there are multiple API doc changes, do not apply subsystem tags for now
   if (isExclusive &&
       labels.includes('doc') &&
       labels.length > 2) {
     const nonDocLabels = labels.filter((val) => {
       return val !== 'doc'
     })
-    if (hasAllSubsystems(nonDocLabels)) {
+    if (hasAllSubsystems(nonDocLabels) || hasAllDocChanges(filepathsChanged)) {
       labels = ['doc']
     } else {
       labels = []

test/unit/node-labels.test.js

@@ -419,3 +419,14 @@ tap.test('label: dont-land-on labels for WHATWG URL', (t) => {
 
   t.end()
 })
+
+tap.test('label: doc label for non-subsystem API doc changes', (t) => {
+  const labels = nodeLabels.resolveLabels([
+    'doc/api/_toc.md',
+    'doc/api/all.md'
+  ])
+
+  t.same(labels, ['doc'])
+
+  t.end()
+})