From 9e2918640a05130650f1899f380a546691ebd926 Mon Sep 17 00:00:00 2001
From: MT Lewis <mtlewis@users.noreply.github.com>
Date: Sat, 27 Jul 2024 14:28:55 +0100
Subject: [PATCH] yarn-plugin: implement BackstageResolver#getSatisfying

It turns out this method is called for
`backstage:` descriptors during `yarn dedupe`, so
we need to implement it.

Signed-off-by: MT Lewis <mtlewis@users.noreply.github.com>
---
 .../src/resolver/BackstageResolver.test.ts    | 83 +++++++++++++++++++
 .../src/resolver/BackstageResolver.ts         | 31 +++++--
 2 files changed, 106 insertions(+), 8 deletions(-)

diff --git a/packages/yarn-plugin/src/resolver/BackstageResolver.test.ts b/packages/yarn-plugin/src/resolver/BackstageResolver.test.ts
index 4cc0c1c9f2..e404970b23 100644
--- a/packages/yarn-plugin/src/resolver/BackstageResolver.test.ts
+++ b/packages/yarn-plugin/src/resolver/BackstageResolver.test.ts
@@ -178,4 +178,87 @@ describe('BackstageResolver', () => {
       ).rejects.toThrow(/invalid backstage version/i);
     });
   });
+
+  describe('getSatisfying', () => {
+    it('filters out locators for other packages', async () => {
+      await expect(
+        backstageResolver.getSatisfying(
+          structUtils.makeDescriptor(
+            structUtils.makeIdent('backstage', 'core'),
+            'backstage:1.23.45',
+          ),
+          {},
+          [
+            structUtils.makeLocator(
+              structUtils.makeIdent('backstage', 'foo'),
+              'npm:1.2.3',
+            ),
+            structUtils.makeLocator(
+              structUtils.makeIdent('backstage', 'core'),
+              'npm:6.7.8',
+            ),
+            structUtils.makeLocator(
+              structUtils.makeIdent('backstage', 'bar'),
+              'npm:1.2.3',
+            ),
+          ],
+        ),
+      ).resolves.toEqual({
+        locators: [
+          structUtils.makeLocator(
+            structUtils.makeIdent('backstage', 'core'),
+            'npm:6.7.8',
+          ),
+        ],
+        sorted: true,
+      });
+    });
+
+    it('filters out locators for other package versions', async () => {
+      await expect(
+        backstageResolver.getSatisfying(
+          structUtils.makeDescriptor(
+            structUtils.makeIdent('backstage', 'core'),
+            'backstage:1.23.45',
+          ),
+          {},
+          [
+            structUtils.makeLocator(
+              structUtils.makeIdent('backstage', 'core'),
+              'npm:5.6.7',
+            ),
+            structUtils.makeLocator(
+              structUtils.makeIdent('backstage', 'core'),
+              'npm:6.7.8',
+            ),
+            structUtils.makeLocator(
+              structUtils.makeIdent('backstage', 'bar'),
+              'npm:7.8.9',
+            ),
+          ],
+        ),
+      ).resolves.toEqual({
+        locators: [
+          structUtils.makeLocator(
+            structUtils.makeIdent('backstage', 'core'),
+            'npm:6.7.8',
+          ),
+        ],
+        sorted: true,
+      });
+    });
+
+    it('throws for non `backstage:` descriptors', async () => {
+      await expect(
+        backstageResolver.getSatisfying(
+          structUtils.makeDescriptor(
+            structUtils.makeIdent('backstage', 'core'),
+            'npm:1.2.3',
+          ),
+          {},
+          [],
+        ),
+      ).rejects.toThrow(/unexpected npm: range/i);
+    });
+  });
 });
diff --git a/packages/yarn-plugin/src/resolver/BackstageResolver.ts b/packages/yarn-plugin/src/resolver/BackstageResolver.ts
index 33bba5df53..82e6c013a3 100644
--- a/packages/yarn-plugin/src/resolver/BackstageResolver.ts
+++ b/packages/yarn-plugin/src/resolver/BackstageResolver.ts
@@ -92,6 +92,29 @@ export class BackstageResolver implements Resolver {
     ];
   }
 
+  /**
+   * Given a descriptor and a list of possible locators, return a filtered list
+   * containing only locators that satisfy the descriptor. Since each Backstage
+   * release version corresponds to a single version for each package, we just
+   * need to filter that array for locators with that exact version.
+   */
+  async getSatisfying(
+    descriptor: Descriptor,
+    _dependencies: Record<string, Package>,
+    locators: Array<Locator>,
+  ): Promise<{ locators: Locator[]; sorted: boolean }> {
+    const packageVersion = await getPackageVersion(descriptor);
+
+    return {
+      locators: locators.filter(
+        locator =>
+          structUtils.areIdentsEqual(descriptor, locator) &&
+          locator.reference === `npm:${packageVersion}`,
+      ),
+      sorted: true,
+    };
+  }
+
   /**
    * This plugin does not need to support any locators itself, since the
    * `getCandidates` method will always convert `backstage:` versions into
@@ -106,14 +129,6 @@ export class BackstageResolver implements Resolver {
    */
   getResolutionDependencies = () => ({});
 
-  /**
-   * Candidate versions produced by this resolver always use the `npm:`
-   *  protocol, so this function will never be called.
-   */
-  async getSatisfying(): Promise<{ locators: Locator[]; sorted: boolean }> {
-    throw new Error('Unreachable');
-  }
-
   /**
    * Once transformed into locators (through getCandidates), the versions are
    * resolved by the NpmSemverResolver