Updated config docs with default transform value (#8583)

* Updated config docs - transform

I've added a default option to clear up any confusion, hopefully that will make it more obvious how it should be added back in  when additional transformers are added.

* Updated change log for #8583

* Update docs/Configuration.md

Co-Authored-By: Tim Seckinger <seckinger.tim@gmail.com>

* Update Configuration.md

* transform is an object instead of array - fixing.

* --amend

* update versioned docs

Co-authored-by: Tim Seckinger <seckinger.tim@gmail.com>
Co-authored-by: Michał Pierzchała <thymikee@gmail.com>

CHANGELOG.md

@@ -20,6 +20,7 @@
 - `[expect, jest-mock, pretty-format]` [**BREAKING**] Remove `build-es5` from package ([#9945](https://github.com/facebook/jest/pull/9945))
 - `[jest-haste-map]` [**BREAKING**] removed `providesModuleNodeModules` ([#8535](https://github.com/facebook/jest/pull/8535))
 - `[docs]` Fix example reference implementation to use Jest with Phabricator ([#8662](https://github.com/facebook/jest/pull/8662))
+- `[docs]` Added default compiler to tranform ([#8583](https://github.com/facebook/jest/pull/8583))
 
 ### Performance
 

docs/Configuration.md

@@ -1119,7 +1119,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, pathToTransformer | [pathToTransformer, object]>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -1134,7 +1134,7 @@ You can pass configuration to a transformer like `{filePattern: ['path-to-transf
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]
 

website/versioned_docs/version-22.x/Configuration.md

@@ -835,7 +835,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, string>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -848,7 +848,7 @@ Examples of such compilers include:
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]
 

website/versioned_docs/version-23.x/Configuration.md

@@ -904,7 +904,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, string>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -917,7 +917,7 @@ Examples of such compilers include:
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]
 

website/versioned_docs/version-24.x/Configuration.md

@@ -1092,7 +1092,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, pathToTransformer | [pathToTransformer, object]>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -1107,7 +1107,7 @@ You can pass configuration to a transformer like `{filePattern: ['path-to-transf
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]
 

website/versioned_docs/version-25.1/Configuration.md

@@ -1107,7 +1107,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, pathToTransformer | [pathToTransformer, object]>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -1122,7 +1122,7 @@ You can pass configuration to a transformer like `{filePattern: ['path-to-transf
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]
 

website/versioned_docs/version-25.3/Configuration.md

@@ -1120,7 +1120,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, pathToTransformer | [pathToTransformer, object]>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -1135,7 +1135,7 @@ You can pass configuration to a transformer like `{filePattern: ['path-to-transf
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]
 

website/versioned_docs/version-25.5/Configuration.md

@@ -1120,7 +1120,7 @@ Setting this value to `fake` allows the use of fake timers for functions such as
 
 ### `transform` [object\<string, pathToTransformer | [pathToTransformer, object]>]
 
-Default: `undefined`
+Default: `{"^.+\\.[jt]sx?$": "babel-jest"}`
 
 A map from regular expressions to paths to transformers. A transformer is a module that provides a synchronous function for transforming source files. For example, if you wanted to be able to use a new language feature in your modules or tests that isn't yet supported by node, you might plug in one of many compilers that compile a future version of JavaScript to a current one. Example: see the [examples/typescript](https://github.com/facebook/jest/blob/master/examples/typescript/package.json#L16) example or the [webpack tutorial](Webpack.md).
 
@@ -1135,7 +1135,7 @@ You can pass configuration to a transformer like `{filePattern: ['path-to-transf
 
 _Note: a transformer is only run once per file unless the file has changed. During development of a transformer it can be useful to run Jest with `--no-cache` to frequently [delete Jest's cache](Troubleshooting.md#caching-issues)._
 
-_Note: if you are using the `babel-jest` transformer and want to use an additional code preprocessor, keep in mind that when "transform" is overwritten in any way the `babel-jest` is not loaded automatically anymore. If you want to use it to compile JavaScript code it has to be explicitly defined. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
+_Note: when adding additional code transformers, this will overwrite the default config and `babel-jest` is no longer automatically loaded. If you want to use it to compile JavaScript or Typescript, it has to be explicitly defined by adding `{"^.+\\.[jt]sx?$": "babel-jest"}` to the transform property. See [babel-jest plugin](https://github.com/facebook/jest/tree/master/packages/babel-jest#setup)_
 
 ### `transformIgnorePatterns` [array\<string>]