doc,tools: get altDocs versions from CHANGELOG.md

Parse `CHANGELOG.md` for versions of Node.js used by the documentation
feature `View another version` so that we don't have to manually update
the list when we cut a new version or transition a release to LTS.

PR-URL: https://github.com/nodejs/node/pull/27661
Reviewed-By: Rich Trott <rtrott@gmail.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/test/internet/test-doctool-versions.js b/test/internet/test-doctool-versions.js
new file mode 100644
index 0000000000..8bb4f81c79
--- /dev/null
+++ b/test/internet/test-doctool-versions.js
@@ -0,0 +1,59 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const util = require('util');
+const { versions } = require('../../tools/doc/versions.js');
+
+// At the time of writing these are the minimum expected versions.
+// New versions of Node.js do not have to be explicitly added here.
+const expected = [
+  '12.x',
+  '11.x',
+  '10.x',
+  '9.x',
+  '8.x',
+  '7.x',
+  '6.x',
+  '5.x',
+  '4.x',
+  '0.12.x',
+  '0.10.x',
+];
+
+async function test() {
+  const vers = await versions();
+  // Coherence checks for each returned version.
+  for (const version of vers) {
+    const tested = util.inspect(version);
+    const parts = version.num.split('.');
+    const expectedLength = parts[0] === '0' ? 3 : 2;
+    assert.strictEqual(parts.length, expectedLength,
+                       `'num' from ${tested} should be '<major>.x'.`);
+    assert.strictEqual(parts[parts.length - 1], 'x',
+                       `'num' from ${tested} doesn't end in '.x'.`);
+    const isEvenRelease = Number.parseInt(parts[expectedLength - 2]) % 2 === 0;
+    const hasLtsProperty = version.hasOwnProperty('lts');
+    if (hasLtsProperty) {
+      // Odd-numbered versions of Node.js are never LTS.
+      assert.ok(isEvenRelease, `${tested} should not be an 'lts' release.`);
+      assert.ok(version.lts, `'lts' from ${tested} should 'true'.`);
+    }
+  }
+
+  // Check that the minimum number of versions were returned.
+  // Later versions are allowed, but not checked for here (they were checked
+  // above).
+  // Also check for the previous semver major -- From master this will be the
+  // most recent major release.
+  const thisMajor = Number.parseInt(process.versions.node.split('.')[0]);
+  const prevMajorString = `${thisMajor - 1}.x`;
+  if (!expected.includes(prevMajorString)) {
+    expected.unshift(prevMajorString);
+  }
+  for (const version of expected) {
+    assert.ok(vers.find((x) => x.num === version),
+              `Did not find entry for '${version}' in ${util.inspect(vers)}`);
+  }
+}
+test();