From feaee22c20b982d9a0b86d38aaa75a17e3ff3386 Mon Sep 17 00:00:00 2001
From: Suneil Nyamathi <snyamathi@gmail.com>
Date: Thu, 1 Feb 2018 13:07:36 -0800
Subject: [PATCH] Handle prerelease version nuances (#5)

---
 src/semver-intersect.js        | 30 +++++++++++++++++++++++-----
 tests/unit/semver-intersect.js | 36 ++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 5 deletions(-)

diff --git a/src/semver-intersect.js b/src/semver-intersect.js
index 12f09fa..e15997a 100644
--- a/src/semver-intersect.js
+++ b/src/semver-intersect.js
@@ -47,11 +47,26 @@ function createShorthand (range) {
 }
 
 function ensureCompatible(range, ...bounds) {
-    const { version } = parseRange(range);
+    const { prerelease, version } = parseRange(range);
+
     bounds.forEach(bound => {
-        if (bound && !semver.satisfies(version, bound)) {
-            throw new Error(`Range ${range} is not compatible with ${bound}`);
+        if (!bound || semver.satisfies(version, bound)) {
+            return;
+        }
+
+        if (prerelease) {
+            if (parseRange(bound).prerelease) {
+                // If both bounds are pre-release versions, either can satisfy the other
+                if (semver.satisfies(parseRange(bound).version, range)) {
+                    return;
+                }
+            } else if (semver.satisfies(version, `${range} ${bound}`)) {
+                // If only our version is a pre-release version, don't fail on 1.0.0-a <2.0.0
+                return;
+            }
         }
+
+        throw new Error(`Range ${range} is not compatible with ${bound}`);
     });
 }
 
@@ -75,7 +90,11 @@ function intersect (...ranges) {
     ranges = expandRanges(...ranges);
 
     const bounds = ranges.reduce(({ lowerBound, upperBound }, range) => {
-        const { condition } = parseRange(range);
+        const { condition, prerelease } = parseRange(range);
+
+        if (prerelease) {
+            ensureCompatible(range, lowerBound, upperBound);
+        }
 
         // Exact version number specified, must be compatible with both bounds
         if (condition === '=') {
@@ -127,7 +146,8 @@ function mergeBounds (range, bound) {
 function parseRange (range) {
     const condition = regex.condition.exec(range)[1] || '=';
     const version = regex.version.exec(range)[1];
-    return { condition, version };
+    const prerelease = semver.prerelease(version);
+    return { condition, prerelease, version };
 }
 
 function union (a, b) {
diff --git a/tests/unit/semver-intersect.js b/tests/unit/semver-intersect.js
index e791c0f..c5a28dc 100644
--- a/tests/unit/semver-intersect.js
+++ b/tests/unit/semver-intersect.js
@@ -138,6 +138,39 @@ describe('intersect', () => {
         const result = intersect('^4.0.0', '~4.3.0');
         expect(result).to.equal('~4.3.0');
     });
+    it('should handle pre-release versions mixed with versions', () => {
+        const result = intersect('^1.0.0-alpha.3', '^1.2.0');
+        expect(result).to.equal('^1.2.0');
+    });
+    it('should handle compatible pre-release versions', () => {
+        const result = intersect('^1.0.0-alpha.3', '^1.0.0-alpha.4');
+        expect(result).to.equal('^1.0.0-alpha.4');
+    });
+    it('should handle compatible pre-release versions without a dot', () => {
+        const result = intersect('^0.14.0-beta2', '^0.14.0-beta3');
+        expect(result).to.equal('^0.14.0-beta3');
+    });
+    it('should handle compatible pre-release versions with the same preid', () => {
+        const result = intersect('^0.14.0-beta', '^0.14.0-beta4');
+        expect(result).to.equal('^0.14.0-beta4');
+    });
+    it('should handle incompatible pre-release versions (different patch version)', () => {
+        const call = intersect.bind(null, '^1.9.0-alpha', '^1.9.1-alpha');
+        expect(call).to.throw('Range >=1.9.1-alpha is not compatible with >=1.9.0-alpha');
+    });
+    it('should handle compatible pre-release versions (preid lower in alphabetical order)', () => {
+        expect(intersect('^1.9.0-alpha', '^1.9.0-beta')).to.equal('^1.9.0-beta');
+        expect(intersect('^1.9.0-beta', '^1.9.0-alpha')).to.equal('^1.9.0-beta');
+        expect(intersect('^1.9.0-alpha.1', '^1.9.0-beta.2')).to.equal('^1.9.0-beta.2');
+    });
+    it('should handle incompatible pre-release versions (specific version)', () => {
+        expect(intersect.bind(null, '1.9.0-alpha.1', '^1.9.0-alpha.2'))
+            .to.throw('Range >=1.9.0-alpha.2 is not compatible with <=1.9.0-alpha.1');
+        expect(intersect.bind(null, '1.9.0-alpha.1', '1.9.0-alpha.0'))
+            .to.throw('Range 1.9.0-alpha.0 is not compatible with >=1.9.0-alpha.1');
+        expect(intersect.bind(null, '1.9.0-rc3', '^1.9.0-rc4'))
+            .to.throw('Range >=1.9.0-rc4 is not compatible with <=1.9.0-rc3');
+    });
     it('should return an exact version intersected with a range', () => {
         const result = intersect('1.5.16', '^1.0.0');
         expect(result).to.equal('1.5.16');
@@ -173,14 +206,17 @@ describe('parseRange', () => {
     it('return the comparison condition and version', () => {
         expect(parseRange('<5.0.0')).to.deep.equal({
             condition: '<',
+            prerelease: null,
             version: '5.0.0'
         });
         expect(parseRange('>=4.0.0')).to.deep.equal({
             condition: '>=',
+            prerelease: null,
             version: '4.0.0'
         });
         expect(parseRange('3.0.0')).to.deep.equal({
             condition: '=',
+            prerelease: null,
             version: '3.0.0'
         });
     });