docs(common): add validators docs

packages/common/pipes/file/file-type.validator.ts

@@ -4,6 +4,13 @@ export type FileTypeValidatorOptions = {
   fileType: string;
 };
 
+/**
+ * Defines the built-in FileType File Validator
+ *
+ * @see [File Validators](https://docs.nestjs.com/techniques/file-upload#validators)
+ *
+ * @publicApi
+ */
 export class FileTypeValidator extends FileValidator<FileTypeValidatorOptions> {
   buildErrorMessage(): string {
     return `Validation failed (expected type is ${this.validationOptions.fileType})`;

packages/common/pipes/file/file-validator.interface.ts

@@ -1,6 +1,18 @@
+/**
+ * Interface describing FileValidators, which can be added to a {@link ParseFilePipe}.
+ */
 export abstract class FileValidator<TValidationOptions = Record<string, any>> {
   constructor(protected readonly validationOptions: TValidationOptions) {}
 
+  /**
+   * Indicates if this file should be considered valid, according to the options passed in the constructor.
+   * @param file the file from the request object
+   */
   abstract isValid(file?: any): boolean;
+
+  /**
+   * Builds an error message in case the validation fails.
+   * @param file the file from the request object
+   */
   abstract buildErrorMessage(file: any): string;
 }

packages/common/pipes/file/max-file-size.validator.ts

@@ -4,6 +4,13 @@ export type MaxFileSizeValidatorOptions = {
   maxSize: number;
 };
 
+/**
+ * Defines the built-in MaxSize File Validator
+ *
+ * @see [File Validators](https://docs.nestjs.com/techniques/file-upload#validators)
+ *
+ * @publicApi
+ */
 export class MaxFileSizeValidator extends FileValidator<MaxFileSizeValidatorOptions> {
   buildErrorMessage(): string {
     return `Validation failed (expected size is less than ${this.validationOptions.maxSize})`;

packages/common/pipes/file/parse-file.pipe.ts

@@ -5,6 +5,16 @@ import { PipeTransform } from '../../interfaces/features/pipe-transform.interfac
 import { ParseFileOptions } from './parse-file-options.interface';
 import { FileValidator } from './file-validator.interface';
 
+/**
+ * Defines the built-in ParseFile Pipe. This pipe can be used to validate incoming files
+ * with `@UploadedFile()` decorator. You can use either other specific built-in validators
+ * or provide one of your own, simply implementing it through {@link FileValidator}
+ * interface and adding it to ParseFilePipe's constructor.
+ *
+ * @see [Built-in Pipes](https://docs.nestjs.com/pipes#built-in-pipes)
+ *
+ * @publicApi
+ */
 @Injectable()
 export class ParseFilePipe implements PipeTransform<any> {
   protected exceptionFactory: (error: string) => any;
@@ -43,6 +53,9 @@ export class ParseFilePipe implements PipeTransform<any> {
     return file;
   }
 
+  /**
+   * @returns list of validators used in this pipe.
+   */
   getValidators() {
     return this.validators;
   }