From ab7fe3106134f66a051db10c7c38befc873f08ad Mon Sep 17 00:00:00 2001
From: Vincent Gao <gaobing1230@gmail.com>
Date: Sat, 4 Jul 2026 23:47:27 +0200
Subject: [PATCH] fix: intersects() false-negative for <0.0.0-<prerelease>
 comparators

---
 classes/comparator.js                    |  3 +-
 test/fixtures/comparator-intersection.js |  9 +++++
 test/fixtures/range-intersection.js      |  6 +++
 test/ranges/intersects.js                | 49 ++++++++++++++++++++++++
 4 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/classes/comparator.js b/classes/comparator.js
index 647c1f09..b9df8d7c 100644
--- a/classes/comparator.js
+++ b/classes/comparator.js
@@ -100,8 +100,9 @@ class Comparator {
       (this.value === '<0.0.0-0' || comp.value === '<0.0.0-0')) {
       return false
     }
+    const isNullSet = v => v === '<0.0.0' || v === '<0.0.0-0'
     if (!options.includePrerelease &&
-      (this.value.startsWith('<0.0.0') || comp.value.startsWith('<0.0.0'))) {
+      (isNullSet(this.value) || isNullSet(comp.value))) {
       return false
     }
 
diff --git a/test/fixtures/comparator-intersection.js b/test/fixtures/comparator-intersection.js
index 08c4bc08..9ca7d1a9 100644
--- a/test/fixtures/comparator-intersection.js
+++ b/test/fixtures/comparator-intersection.js
@@ -41,4 +41,13 @@ module.exports = [
   ['<0.1.0', '<0.0.0-0', false],
   ['<0.0.0-0', '<0.1.0', false, true],
   ['<0.1.0', '<0.0.0-0', false, true],
+  // A `<0.0.0-<id>` comparator (with a non-minimal prerelease) is NOT the empty
+  // set: it matches prereleases below `<id>` such as `0.0.0-0`, so it can
+  // intersect other ranges. Only `<0.0.0` and `<0.0.0-0` match nothing. See #521.
+  ['<0.0.0-rc.1', '>=0.0.0-alpha.0', true],
+  ['<0.0.0-rc.1', '>0.0.0-alpha.0', true],
+  ['<0.0.0-beta', '>=0.0.0-alpha', true],
+  ['<0.0.0-alpha', '<0.0.0-rc.1', true],
+  ['<0.0.0', '>=0.0.0-alpha.0', false],
+  ['<0.0.0', '>0.0.0-alpha.0', false],
 ]
diff --git a/test/fixtures/range-intersection.js b/test/fixtures/range-intersection.js
index 217bee22..41e21fb0 100644
--- a/test/fixtures/range-intersection.js
+++ b/test/fixtures/range-intersection.js
@@ -58,4 +58,10 @@ module.exports = [
   ['1.x', '1.3.0 || <1.0.0 >2.0.0', true],
   ['*', '*', true],
   ['x', '', true],
+  // `<0.0.0-<id>` matches prereleases below `<id>`, so it can intersect ranges
+  // that also admit those prereleases; only `<0.0.0`/`<0.0.0-0` are empty. #521
+  ['<0.0.0-rc.1', '~0.0.0-alpha.0', true],
+  ['<0.0.0-rc.1 <=0.3.2-0', '~0.0.0-alpha.0 || 1', true],
+  ['<0.0.0', '0.x', false],
+  ['<0.0.0', '>=0.0.0-alpha.0', false],
 ]
diff --git a/test/ranges/intersects.js b/test/ranges/intersects.js
index e3d9c88c..88df093c 100644
--- a/test/ranges/intersects.js
+++ b/test/ranges/intersects.js
@@ -2,6 +2,7 @@
 
 const { test } = require('tap')
 const intersects = require('../../ranges/intersects')
+const satisfies = require('../../functions/satisfies')
 const Range = require('../../classes/range')
 const Comparator = require('../../classes/comparator')
 const comparatorIntersection = require('../fixtures/comparator-intersection.js')
@@ -58,3 +59,51 @@ test('missing comparator parameter in intersect comparators', (t) => {
   'throws type error')
   t.end()
 })
+
+// Differential oracle: if a concrete version satisfies BOTH ranges, then the
+// ranges MUST intersect. This densely samples the near-zero / prerelease space
+// where `<0.0.0-<id>` comparators live, guarding against the over-broad
+// `startsWith('<0.0.0')` empty-range check that wrongly treated e.g.
+// `<0.0.0-rc.1` (which matches `0.0.0-0`, `0.0.0-alpha`, ...) as matching
+// nothing, producing false negatives from `intersects`.
+test('intersects agrees with pointwise satisfaction', t => {
+  const nums = [0, 1, 2]
+  const pres = ['', '-0', '-alpha', '-alpha.0', '-alpha.1', '-beta', '-rc.1', '-rc.2']
+  const grid = []
+  for (const a of nums) {
+    for (const b of nums) {
+      for (const c of nums) {
+        for (const p of pres) {
+          grid.push(`${a}.${b}.${c}${p}`)
+        }
+      }
+    }
+  }
+
+  const anchors = ['0.0.0', '0.0.0-0', '0.0.0-alpha', '0.0.0-rc.1',
+    '0.1.0-alpha', '1.0.0-alpha', '1.0.0']
+  const comparators = []
+  for (const op of ['<', '<=', '>', '>=', '']) {
+    for (const v of anchors) {
+      comparators.push(`${op}${v}`)
+    }
+  }
+
+  let witnessBacked = 0
+  for (const opts of [{}, { includePrerelease: true }]) {
+    for (const a of comparators) {
+      for (const b of comparators) {
+        const witness = grid.find(v => satisfies(v, a, opts) && satisfies(v, b, opts))
+        if (witness === undefined) {
+          continue
+        }
+        witnessBacked++
+        const label = `${JSON.stringify(opts)}: ${witness} satisfies both`
+        t.equal(intersects(a, b, opts), true, `${a} ∩ ${b} (${label})`)
+        t.equal(intersects(b, a, opts), true, `${b} ∩ ${a} symmetry (${label})`)
+      }
+    }
+  }
+  t.ok(witnessBacked > 100, `exercised ${witnessBacked} witness-backed pairs`)
+  t.end()
+})