Correct semver.intersect impl; Fixes pkgxdev#156

src/utils/semver.ts

@@ -237,15 +237,25 @@ export function intersect(a: Range, b: Range): Range {
   if (a.set === '*') return b
   if (a.eq(b)) return a
 
-  if (a.set.length == 1 && b.set.length == 1) {
-    const [c,d] = [a.set[0], b.set[0]]
-    const e = c[0].gt(d[0]) ? c[0] : d[0]
-    const f = c[1].gt(d[1]) ? c[1] : d[1]
-    a.set = [[e,f]]
-    return a
+  // calculate the intersection between two semver.Ranges
+  const set: [SemVer, SemVer][] = []
+
+  for (let i = 0; i < a.set.length; i++) {
+    for (let j = 0; j < b.set.length; j++) {
+      const a1 = a.set[i][0]
+      const a2 = a.set[i][1]
+      const b1 = b.set[j][0]
+      const b2 = b.set[j][1]
+
+      if (a1.compare(b2) >= 0 || b1.compare(a2) >= 0) {
+        continue
+      }
+
+      set.push([a1.compare(b1) > 0 ? a1 : b1, a2.compare(b2) < 0 ? a2 : b2])
+    }
   }
 
-  throw new Error(`couldn’t intersect ${a} and ${b}`)
+  return new Range(set.map(([v1, v2]) => `>=${chomp(v1)}<${chomp(v2)}`).join(","))
 }
 
 

tests/unit/semver.test.ts

@@ -58,4 +58,43 @@ Deno.test("semver", async test => {
     const e = new semver.Range("~1")
     assertEquals(e.toString(), "^1")  // indeed: we change the ~ to ^
   })
+
+  await test.step("intersection", async test => {
+    await test.step("^3.7…@3.11", () => {
+      const a = new semver.Range("^3.7")
+      const b = new semver.Range("3.11.0")
+
+      assertEquals(b.toString(), "@3.11.0")
+
+      const c = semver.intersect(a, b)
+      assertEquals(c.toString(), "@3.11.0")
+    })
+
+    await test.step("^3.7…^3.9", () => {
+      const a = new semver.Range("^3.7")
+      const b = new semver.Range("^3.9")
+
+      assertEquals(b.toString(), "^3.9")
+
+      const c = semver.intersect(a, b)
+      assertEquals(c.toString(), "^3.9")
+    })
+
+    await test.step("^3.7…*", () => {
+      const a = new semver.Range("^3.7")
+      const b = new semver.Range("*")
+
+      assertEquals(b.toString(), "*")
+
+      const c = semver.intersect(a, b)
+      assertEquals(c.toString(), "^3.7")
+    })
+
+    await test.step("~3.7…~3.8", () => {
+      const a = new semver.Range("~3.7")
+      const b = new semver.Range("~3.8")
+
+      assertThrows(() => semver.intersect(a, b))
+    })
+  })
 })