Alternative approach for findSchemaChanges (graphql#4235)

Alternative to graphql#2181

This adds a new `findSchemaChanges` export and deprecates the breaking
and dangerous alternative to be removed in v18. While adding
safe-schema-changes I noticed that we lack directive arg validation
here, we should probably add these to breaking/dangerous changes in the
future.

src/index.ts

@@ -477,8 +477,10 @@ export {
   // Compares two GraphQLSchemas and detects breaking changes.
   BreakingChangeType,
   DangerousChangeType,
+  SafeChangeType,
   findBreakingChanges,
   findDangerousChanges,
+  findSchemaChanges,
 } from './utilities/index.js';
 
 export type {
@@ -506,6 +508,7 @@ export type {
   IntrospectionDirective,
   BuildSchemaOptions,
   BreakingChange,
+  SafeChange,
   DangerousChange,
   TypedQueryDocumentNode,
 } from './utilities/index.js';

src/utilities/__tests__/findBreakingChanges-test.ts

@@ -16,7 +16,7 @@ import {
   DangerousChangeType,
   findBreakingChanges,
   findDangerousChanges,
-} from '../findBreakingChanges.js';
+} from '../findSchemaChanges.js';
 
 describe('findBreakingChanges', () => {
   it('should detect if a type was removed or not', () => {

src/utilities/__tests__/findSchemaChanges-test.ts

@@ -0,0 +1,180 @@
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import { buildSchema } from '../buildASTSchema.js';
+import { findSchemaChanges, SafeChangeType } from '../findSchemaChanges.js';
+
+describe('findSchemaChanges', () => {
+  it('should detect if a type was added', () => {
+    const newSchema = buildSchema(`
+      type Type1
+      type Type2
+    `);
+
+    const oldSchema = buildSchema(`
+      type Type1
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        type: SafeChangeType.TYPE_ADDED,
+        description: 'Type2 was added.',
+      },
+    ]);
+  });
+
+  it('should detect if a field was added', () => {
+    const oldSchema = buildSchema(`
+      type Query {
+        foo: String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      type Query {
+        foo: String
+        bar: String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        type: SafeChangeType.FIELD_ADDED,
+        description: 'Field Query.bar was added.',
+      },
+    ]);
+  });
+
+  it('should detect if a default value was added', () => {
+    const oldSchema = buildSchema(`
+      type Query {
+        foo(x: String): String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      type Query {
+        foo(x: String = "bar"): String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        type: SafeChangeType.ARG_DEFAULT_VALUE_ADDED,
+        description: 'Query.foo(x:) added a defaultValue "bar".',
+      },
+    ]);
+  });
+
+  it('should detect if an arg value changes safely', () => {
+    const oldSchema = buildSchema(`
+      type Query {
+        foo(x: String!): String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      type Query {
+        foo(x: String): String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        type: SafeChangeType.ARG_CHANGED_KIND_SAFE,
+        description:
+          'Argument Query.foo(x:) has changed type from String! to String.',
+      },
+    ]);
+  });
+
+  it('should detect if a directive was added', () => {
+    const oldSchema = buildSchema(`
+      type Query {
+        foo: String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      directive @Foo on FIELD_DEFINITION
+
+      type Query {
+        foo: String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        description: 'Directive @Foo was added.',
+        type: SafeChangeType.DIRECTIVE_ADDED,
+      },
+    ]);
+  });
+
+  it('should detect if a directive becomes repeatable', () => {
+    const oldSchema = buildSchema(`
+      directive @Foo on FIELD_DEFINITION
+
+      type Query {
+        foo: String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      directive @Foo repeatable on FIELD_DEFINITION
+
+      type Query {
+        foo: String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        description: 'Repeatable flag was added to @Foo.',
+        type: SafeChangeType.DIRECTIVE_REPEATABLE_ADDED,
+      },
+    ]);
+  });
+
+  it('should detect if a directive adds locations', () => {
+    const oldSchema = buildSchema(`
+      directive @Foo on FIELD_DEFINITION
+
+      type Query {
+        foo: String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      directive @Foo on FIELD_DEFINITION | QUERY
+
+      type Query {
+        foo: String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        description: 'QUERY was added to @Foo.',
+        type: SafeChangeType.DIRECTIVE_LOCATION_ADDED,
+      },
+    ]);
+  });
+
+  it('should detect if a directive arg gets added', () => {
+    const oldSchema = buildSchema(`
+      directive @Foo on FIELD_DEFINITION
+
+      type Query {
+        foo: String
+      }
+    `);
+
+    const newSchema = buildSchema(`
+      directive @Foo(arg1: String) on FIELD_DEFINITION
+
+      type Query {
+        foo: String
+      }
+    `);
+    expect(findSchemaChanges(oldSchema, newSchema)).to.deep.equal([
+      {
+        description: 'An optional argument @Foo(arg1:) was added.',
+        type: SafeChangeType.OPTIONAL_DIRECTIVE_ARG_ADDED,
+      },
+    ]);
+  });
+});