config-loader: collect schemas from each package version

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/nervous-months-teach.md

@@ -0,0 +1,5 @@
+---
+'@backstage/config-loader': patch
+---
+
+Allow collection of configuration schemas from multiple versions of the same package.

packages/config-loader/src/lib/schema/collect.test.ts

@@ -231,6 +231,74 @@ describe('collectConfigSchemas', () => {
     ]);
   });
 
+  it('should load schema from different package versions', async () => {
+    mockFs({
+      node_modules: {
+        a: {
+          'package.json': JSON.stringify({
+            name: 'a',
+            dependencies: {
+              b: '1',
+              c: '1',
+            },
+            configSchema: mockSchema,
+          }),
+        },
+        b: {
+          'package.json': JSON.stringify({
+            name: 'b',
+            version: '1',
+            dependencies: {
+              c: '2',
+            },
+            configSchema: { ...mockSchema, title: 'b' },
+          }),
+          node_modules: {
+            c: {
+              'package.json': JSON.stringify({
+                name: 'c',
+                version: '2',
+                configSchema: { ...mockSchema, title: 'c2' },
+              }),
+            },
+          },
+        },
+        c: {
+          'package.json': JSON.stringify({
+            name: 'c',
+            version: '1',
+            configSchema: { ...mockSchema, title: 'c1' },
+          }),
+        },
+      },
+    });
+
+    await expect(collectConfigSchemas(['a'], [])).resolves.toEqual([
+      {
+        path: path.join('node_modules', 'a', 'package.json'),
+        value: mockSchema,
+      },
+      {
+        path: path.join('node_modules', 'b', 'package.json'),
+        value: { ...mockSchema, title: 'b' },
+      },
+      {
+        path: path.join('node_modules', 'c', 'package.json'),
+        value: { ...mockSchema, title: 'c1' },
+      },
+      {
+        path: path.join(
+          'node_modules',
+          'b',
+          'node_modules',
+          'c',
+          'package.json',
+        ),
+        value: { ...mockSchema, title: 'c2' },
+      },
+    ]);
+  });
+
   it('should not allow unknown schema file types', async () => {
     mockFs({
       node_modules: {

packages/config-loader/src/lib/schema/collect.ts

@@ -43,9 +43,10 @@ export async function collectConfigSchemas(
   packageNames: string[],
   packagePaths: string[],
 ): Promise<ConfigSchemaPackageEntry[]> {
-  const visitedPackages = new Set<string>();
-  const schemas = Array<ConfigSchemaPackageEntry>();
-  const tsSchemaPaths = Array<string>();
+  const schemas = new Array<ConfigSchemaPackageEntry>();
+  const tsSchemaPaths = new Array<string>();
+  const visitedPackageVersions = new Map<string, Set<string>>(); // pkgName: [versions...]
+
   const currentDir = await fs.realpath(process.cwd());
 
   async function processItem(item: Item) {
@@ -59,16 +60,6 @@ export async function collectConfigSchemas(
     } else if (item.name) {
       const { name, parentPath } = item;
 
-      // Ensures that we only process each package once. We don't bother with
-      // loading in schemas from duplicates of different versions, as that's not
-      // supported by Backstage right now anyway. We may want to change that in
-      // the future though, if it for example becomes possible to load in two
-      // different versions of e.g. @backstage/core at once.
-      if (visitedPackages.has(name)) {
-        return;
-      }
-      visitedPackages.add(name);
-
       try {
         pkgPath = req.resolve(
           `${name}/package.json`,
@@ -86,6 +77,18 @@ export async function collectConfigSchemas(
     }
 
     const pkg = await fs.readJson(pkgPath);
+
+    // Ensures that we only process the same version of each package once.
+    let versions = visitedPackageVersions.get(pkg.name);
+    if (versions?.has(pkg.version)) {
+      return;
+    }
+    if (!versions) {
+      versions = new Set();
+      visitedPackageVersions.set(pkg.name, versions);
+    }
+    versions.add(pkg.version);
+
     const depNames = [
       ...Object.keys(pkg.dependencies ?? {}),
       ...Object.keys(pkg.devDependencies ?? {}),