build: add size-tracking bazel test (#30070)

Introduces a new Bazel test that allows us to inspect
what source-files contribute to a given bundled file
and how much bytes they contribute to the bundle size.

Additionally the size-tracking rule groups the size
data by directories. This allows us to compare size
changes in the scope of directories. e.g. a lot of
files in a directory could increase slightly in size, but
in the directory scope the size change could be significant
and needs to be reported by the test target.

Resolves FW-1278

PR Close #30070

tools/size-tracking/file_size_compare_spec.ts

@@ -0,0 +1,92 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {compareFileSizeData} from './file_size_compare';
+
+describe('file size compare', () => {
+
+  it('should report if size entry differ by more than the specified threshold', () => {
+    const diffs = compareFileSizeData(
+        {
+          unmapped: 0,
+          files: {
+            size: 50,
+            'a.ts': 50,
+          }
+        },
+        {
+          unmapped: 0,
+          files: {
+            size: 75,
+            'a.ts': 75,
+          }
+        },
+        0);
+
+    expect(diffs.length).toBe(2);
+    expect(diffs[0].filePath).toBe('/');
+    expect(diffs[0].message).toMatch(/40.00% from the expected size/);
+    expect(diffs[1].filePath).toBe('/a.ts');
+    expect(diffs[1].message).toMatch(/40.00% from the expected size/);
+  });
+
+  it('should not report if size percentage difference does not exceed threshold', () => {
+    const diffs = compareFileSizeData(
+        {
+          unmapped: 0,
+          files: {
+            size: 50,
+            'a.ts': 50,
+          }
+        },
+        {
+          unmapped: 0,
+          files: {
+            size: 75,
+            'a.ts': 75,
+          }
+        },
+        40);
+
+    expect(diffs.length).toBe(0);
+  });
+
+
+  it('should report if expected file size data misses a file size entry', () => {
+    const diffs = compareFileSizeData(
+        {
+          unmapped: 0,
+          files: {
+            size: 101,
+            'a.ts': 100,
+            'b.ts': 1,
+          }
+        },
+        {unmapped: 0, files: {size: 100, 'a.ts': 100}}, 1);
+
+    expect(diffs.length).toBe(1);
+    expect(diffs[0].filePath).toBe('/b.ts');
+    expect(diffs[0].message).toMatch(/Unexpected file.*not part of golden./);
+  });
+
+  it('should report if actual file size data misses an expected file size entry', () => {
+    const diffs = compareFileSizeData(
+        {
+          unmapped: 0,
+          files: {
+            size: 100,
+            'a.ts': 100,
+          }
+        },
+        {unmapped: 0, files: {size: 101, 'a.ts': 100, 'b.ts': 1}}, 1);
+
+    expect(diffs.length).toBe(1);
+    expect(diffs[0].filePath).toBe('/b.ts');
+    expect(diffs[0].message).toMatch(/Expected file.*not included./);
+  });
+});