fix(optimizer): simplify redundant intersections in allOf schemas

src/generator.ts

@@ -20,7 +20,7 @@ export function generate(ast: AST, options = DEFAULT_OPTIONS): string {
   return (
     [
       options.bannerComment,
-      declareNamedTypes(ast, options, ast.standaloneName!),
+      declareNamedTypes(ast, options, ast.standaloneName!, new Set(), new Set()),
       declareNamedInterfaces(ast, options, ast.standaloneName!),
       declareEnums(ast, options),
     ]
@@ -101,18 +101,33 @@ function declareNamedInterfaces(ast: AST, options: Options, rootASTName: string,
   return type
 }
 
-function declareNamedTypes(ast: AST, options: Options, rootASTName: string, processed = new Set<AST>()): string {
+function declareNamedTypes(
+  ast: AST,
+  options: Options,
+  rootASTName: string,
+  processed = new Set<AST>(),
+  outputtedNames = new Set<string>(),
+): string {
   if (processed.has(ast)) {
     return ''
   }
 
   processed.add(ast)
 
+  // Helper to generate standalone type only if name hasn't been used
+  const generateStandaloneTypeOnce = (ast: ASTWithStandaloneName): string | undefined => {
+    if (outputtedNames.has(ast.standaloneName)) {
+      return undefined
+    }
+    outputtedNames.add(ast.standaloneName)
+    return generateStandaloneType(ast, options)
+  }
+
   switch (ast.type) {
     case 'ARRAY':
       return [
-        declareNamedTypes(ast.params, options, rootASTName, processed),
-        hasStandaloneName(ast) ? generateStandaloneType(ast, options) : undefined,
+        declareNamedTypes(ast.params, options, rootASTName, processed, outputtedNames),
+        hasStandaloneName(ast) ? generateStandaloneTypeOnce(ast) : undefined,
       ]
         .filter(Boolean)
         .join('\n')
@@ -123,28 +138,28 @@ function declareNamedTypes(ast: AST, options: Options, rootASTName: string, proc
         .map(
           ast =>
             (ast.standaloneName === rootASTName || options.declareExternallyReferenced) &&
-            declareNamedTypes(ast, options, rootASTName, processed),
+            declareNamedTypes(ast, options, rootASTName, processed, outputtedNames),
         )
         .filter(Boolean)
         .join('\n')
     case 'INTERSECTION':
     case 'TUPLE':
     case 'UNION':
       return [
-        hasStandaloneName(ast) ? generateStandaloneType(ast, options) : undefined,
+        hasStandaloneName(ast) ? generateStandaloneTypeOnce(ast) : undefined,
         ast.params
-          .map(ast => declareNamedTypes(ast, options, rootASTName, processed))
+          .map(ast => declareNamedTypes(ast, options, rootASTName, processed, outputtedNames))
           .filter(Boolean)
           .join('\n'),
         'spreadParam' in ast && ast.spreadParam
-          ? declareNamedTypes(ast.spreadParam, options, rootASTName, processed)
+          ? declareNamedTypes(ast.spreadParam, options, rootASTName, processed, outputtedNames)
           : undefined,
       ]
         .filter(Boolean)
         .join('\n')
     default:
       if (hasStandaloneName(ast)) {
-        return generateStandaloneType(ast, options)
+        return generateStandaloneTypeOnce(ast) || ''
       }
       return ''
   }

src/optimizer.ts

@@ -59,9 +59,85 @@ export function optimize(ast: AST, options: Options, processed = new Set<AST>())
         optimizedAST.params = params
       }
 
-      return Object.assign(optimizedAST, {
-        params: optimizedAST.params.map(_ => optimize(_, options, processed)),
-      })
+      // For INTERSECTION: simplify A & (A | null) -> A | null
+      // Also handle cases where intersection contains duplicate types
+      if (ast.type === 'INTERSECTION') {
+        // First, handle the A & (A | null) -> A | null pattern
+        if (optimizedAST.params.length === 2) {
+          const [first, second] = optimizedAST.params
+
+          // Check if one is INTERFACE and the other is UNION containing that INTERFACE
+          if (first.type === 'INTERFACE' && second.type === 'UNION') {
+            const firstType = generateType(first, options)
+            // Look for an interface member in the union that matches first
+            for (const unionParam of second.params) {
+              if (unionParam.type === 'INTERFACE') {
+                const unionParamType = generateType(unionParam, options)
+                if (firstType === unionParamType) {
+                  // Found a match - check if the rest of the union is just adding null or similar
+                  const otherMembers = second.params.filter(_ => _ !== unionParam)
+                  if (otherMembers.length > 0) {
+                    log('cyan', 'optimizer', 'A & (A | ...) -> A | ...', optimizedAST)
+                    // Preserve standaloneName, keyName, comment from the intersection
+                    return {
+                      ...second,
+                      standaloneName: optimizedAST.standaloneName,
+                      keyName: optimizedAST.keyName,
+                      comment: optimizedAST.comment,
+                      deprecated: optimizedAST.deprecated,
+                    }
+                  }
+                }
+              }
+            }
+          }
+
+          // Check the reverse: (A | ...) & A -> A | ...
+          if (second.type === 'INTERFACE' && first.type === 'UNION') {
+            const secondType = generateType(second, options)
+            // Look for an interface member in the union that matches second
+            for (const unionParam of first.params) {
+              if (unionParam.type === 'INTERFACE') {
+                const unionParamType = generateType(unionParam, options)
+                if (secondType === unionParamType) {
+                  // Found a match - check if the rest of the union is just adding null or similar
+                  const otherMembers = first.params.filter(_ => _ !== unionParam)
+                  if (otherMembers.length > 0) {
+                    log('cyan', 'optimizer', '(A | ...) & A -> A | ...', optimizedAST)
+                    // Preserve standaloneName, keyName, comment from the intersection
+                    return {
+                      ...first,
+                      standaloneName: optimizedAST.standaloneName,
+                      keyName: optimizedAST.keyName,
+                      comment: optimizedAST.comment,
+                      deprecated: optimizedAST.deprecated,
+                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+
+        // Second, handle intersections with more than 2 members that contain duplicates
+        // This handles cases like A & B & A & B -> A & B
+        if (optimizedAST.params.length > 2) {
+          const uniqueParams = uniqBy(optimizedAST.params, _ => generateType(_, options))
+          if (uniqueParams.length < optimizedAST.params.length) {
+            log('cyan', 'optimizer', 'Intersection with duplicates simplified', optimizedAST)
+            optimizedAST.params = uniqueParams
+
+            // If we're left with just 1 param, return it directly
+            if (uniqueParams.length === 1) {
+              log('cyan', 'optimizer', 'Single-member intersection unwrapped', optimizedAST)
+              return uniqueParams[0]
+            }
+          }
+        }
+      }
+
+      // Params were already optimized at line 27, so just return
+      return optimizedAST
     default:
       return ast
   }

test/__snapshots__/test/test.ts.md

@@ -440405,17 +440405,7 @@ Generated by [AVA](https://avajs.dev).
      */␊
     exit_code?: number␊
     [k: string]: unknown␊
-    } & ({␊
-    /**␊
-     * output of the postdeploy script␊
-     */␊
-    output?: string␊
-    /**␊
-     * The exit code of the postdeploy script␊
-     */␊
-    exit_code?: number␊
-    [k: string]: unknown␊
-    } | null))␊
+    } | null)␊
     /**␊
      * buildpacks executed for this build, in order␊
      */␊
@@ -440429,19 +440419,13 @@ Generated by [AVA](https://avajs.dev).
     /**␊
      * release resulting from the build␊
      */␊
-    export type Release = ({␊
+    export type Release = (null | {␊
     /**␊
      * unique identifier of release␊
      */␊
     id?: string␊
     [k: string]: unknown␊
-    } & (null | {␊
-    /**␊
-     * unique identifier of release␊
-     */␊
-    id?: string␊
-    [k: string]: unknown␊
-    }))␊
+    })␊
     /**␊
      * price information for this dyno size␊
      */␊
@@ -440465,17 +440449,7 @@ Generated by [AVA](https://avajs.dev).
      */␊
     name?: string␊
     [k: string]: unknown␊
-    } & ({␊
-    /**␊
-     * unique identifier of add-on␊
-     */␊
-    id?: string␊
-    /**␊
-     * globally unique name of the add-on␊
-     */␊
-    name?: string␊
-    [k: string]: unknown␊
-    } | null))␊
+    } | null)␊
     /**␊
      * The scope of access OAuth authorization allows␊
      */␊
@@ -444001,66 +443975,7 @@ Generated by [AVA](https://avajs.dev).
      * and run json-schema-to-typescript to regenerate this file.␊
      */␊
     ␊
-    export type CoreSchemaMetaSchema = {␊
-      $id?: string;␊
-      $schema?: string;␊
-      $ref?: string;␊
-      $comment?: string;␊
-      title?: string;␊
-      description?: string;␊
-      default?: unknown;␊
-      readOnly?: boolean;␊
-      writeOnly?: boolean;␊
-      examples?: unknown[];␊
-      multipleOf?: number;␊
-      maximum?: number;␊
-      exclusiveMaximum?: number;␊
-      minimum?: number;␊
-      exclusiveMinimum?: number;␊
-      maxLength?: NonNegativeInteger;␊
-      minLength?: NonNegativeIntegerDefault0;␊
-      pattern?: string;␊
-      additionalItems?: CoreSchemaMetaSchema;␊
-      items?: CoreSchemaMetaSchema | SchemaArray;␊
-      maxItems?: NonNegativeInteger;␊
-      minItems?: NonNegativeIntegerDefault0;␊
-      uniqueItems?: boolean;␊
-      contains?: CoreSchemaMetaSchema;␊
-      maxProperties?: NonNegativeInteger;␊
-      minProperties?: NonNegativeIntegerDefault0;␊
-      required?: StringArray;␊
-      additionalProperties?: CoreSchemaMetaSchema;␊
-      definitions?: {␊
-        [k: string]: CoreSchemaMetaSchema;␊
-      };␊
-      properties?: {␊
-        [k: string]: CoreSchemaMetaSchema;␊
-      };␊
-      patternProperties?: {␊
-        [k: string]: CoreSchemaMetaSchema;␊
-      };␊
-      dependencies?: {␊
-        [k: string]: CoreSchemaMetaSchema | StringArray;␊
-      };␊
-      propertyNames?: CoreSchemaMetaSchema;␊
-      const?: unknown;␊
-      /**␊
-       * @minItems 1␊
-       */␊
-      enum?: [unknown, ...unknown[]];␊
-      type?: SimpleTypes | [SimpleTypes, ...SimpleTypes[]];␊
-      format?: string;␊
-      contentMediaType?: string;␊
-      contentEncoding?: string;␊
-      if?: CoreSchemaMetaSchema;␊
-      then?: CoreSchemaMetaSchema;␊
-      else?: CoreSchemaMetaSchema;␊
-      allOf?: SchemaArray;␊
-      anyOf?: SchemaArray;␊
-      oneOf?: SchemaArray;␊
-      not?: CoreSchemaMetaSchema;␊
-      [k: string]: unknown;␊
-    } & (␊
+    export type CoreSchemaMetaSchema =␊
       | {␊
           $id?: string;␊
           $schema?: string;␊
@@ -444121,8 +444036,7 @@ Generated by [AVA](https://avajs.dev).
           not?: CoreSchemaMetaSchema;␊
           [k: string]: unknown;␊
         }␊
-      | boolean␊
-    );␊
+      | boolean;␊
     export type NonNegativeInteger = number;␊
     export type NonNegativeIntegerDefault0 = NonNegativeInteger;␊
     /**␊
@@ -447933,12 +447847,14 @@ Generated by [AVA](https://avajs.dev).
     /**␊
      * A person who has been involved in creating or maintaining this package.␊
      */␊
-    export type Person = {␊
-      name: string;␊
-      url?: string;␊
-      email?: string;␊
-      [k: string]: unknown;␊
-    } & Person1;␊
+    export type Person =␊
+      | {␊
+          name: string;␊
+          url?: string;␊
+          email?: string;␊
+          [k: string]: unknown;␊
+        }␊
+      | string;␊
     export type Person1 =␊
       | {␊
           name: string;␊
@@ -448084,6 +448000,40 @@ Generated by [AVA](https://avajs.dev).
     }␊
     `
 
+## realWorld.tsconfig.js
+
+> Expected output to match snapshot for e2e test: realWorld.tsconfig.js
+
+    `/* eslint-disable */␊
+    /**␊
+     * This file was automatically generated by json-schema-to-typescript.␊
+     * DO NOT MODIFY IT BY HAND. Instead, modify the source JSONSchema file,␊
+     * and run json-schema-to-typescript to regenerate this file.␊
+     */␊
+    ␊
+    export type RealWorld = CompilerOptionsDefinition & TsNodeDefinition;␊
+    export type CompilerOptions = {␊
+      types?: (string | null)[] | null;␊
+      target?: string | null;␊
+      [k: string]: unknown;␊
+    } | null;␊
+    ␊
+    export interface CompilerOptionsDefinition {␊
+      compilerOptions?: CompilerOptions;␊
+      [k: string]: unknown;␊
+    }␊
+    export interface TsNodeDefinition {␊
+      "ts-node"?: {␊
+        compilerOptions?: CompilerOptions &␊
+          ({␊
+            [k: string]: unknown;␊
+          } | null);␊
+        [k: string]: unknown;␊
+      } | null;␊
+      [k: string]: unknown;␊
+    }␊
+    `
+
 ## ref.1a.js
 
 > Expected output to match snapshot for e2e test: ref.1a.js