Improve return types for render, renderAsync, renderFile and `r…

…enderFileAsync` (#199)

resolves #189

src/config.ts

@@ -90,6 +90,7 @@ export interface EtaConfigWithFilename extends EtaConfig {
 }
 
 export type PartialConfig = Partial<EtaConfig>
+export type PartialAsyncConfig = PartialConfig & { async: true }
 
 /* END TYPES */
 

src/file-handlers.ts

@@ -170,14 +170,27 @@ function includeFile(path: string, options: EtaConfig): [TemplateFunction, EtaCo
  * ```
  */
 
+function renderFile(
+  filename: string,
+  data: DataObj,
+  config?: PartialConfig,
+): Promise<string>
+
+function renderFile(
+  filename: string,
+  data: DataObj,
+  config: PartialConfig,
+  cb: CallbackFn
+): void
+
 function renderFile(
   filename: string,
   data: DataObj,
   config?: PartialConfig,
   cb?: CallbackFn
 ): Promise<string> | void
 
-function renderFile(filename: string, data: DataObj, cb?: CallbackFn): Promise<string> | void
+function renderFile(filename: string, data: DataObj, cb: CallbackFn): void
 
 function renderFile(
   filename: string,
@@ -268,14 +281,27 @@ function renderFile(
  * ```
  */
 
+function renderFileAsync(
+  filename: string,
+  data: DataObj,
+  config?: PartialConfig
+): Promise<string>
+
+function renderFileAsync(
+  filename: string,
+  data: DataObj,
+  config: PartialConfig,
+  cb: CallbackFn
+): void
+
 function renderFileAsync(
   filename: string,
   data: DataObj,
   config?: PartialConfig,
   cb?: CallbackFn
 ): Promise<string> | void
 
-function renderFileAsync(filename: string, data: DataObj, cb?: CallbackFn): Promise<string> | void
+function renderFileAsync(filename: string, data: DataObj, cb: CallbackFn): void
 
 function renderFileAsync(
   filename: string,

src/render.ts

@@ -5,7 +5,7 @@ import EtaErr from './err'
 
 /* TYPES */
 
-import type { EtaConfig, PartialConfig } from './config'
+import type { EtaConfig, PartialConfig, PartialAsyncConfig } from './config'
 import type { TemplateFunction } from './compile'
 import type { CallbackFn } from './file-handlers'
 
@@ -45,6 +45,83 @@ function handleCache(template: string | TemplateFunction, options: EtaConfig): T
  * @param config Optional config options
  * @param cb Callback function
  */
+export default function render(
+    template: string | TemplateFunction,
+    data: object,
+    config: PartialAsyncConfig,
+    cb: CallbackFn
+): void
+
+/**
+ * Render a template
+ *
+ * If `template` is a string, Eta will compile it to a function and then call it with the provided data.
+ * If `template` is a template function, Eta will call it with the provided data.
+ *
+ * If `config.async` is `false`, Eta will return the rendered template.
+ *
+ * If `config.async` is `true` and there's a callback function, Eta will call the callback with `(err, renderedTemplate)`.
+ * If `config.async` is `true` and there's not a callback function, Eta will return a Promise that resolves to the rendered template.
+ *
+ * If `config.cache` is `true` and `config` has a `name` or `filename` property, Eta will cache the template on the first render and use the cached template for all subsequent renders.
+ *
+ * @param template Template string or template function
+ * @param data Data to render the template with
+ * @param config Optional config options
+ */
+export default function render(
+    template: string | TemplateFunction,
+    data: object,
+    config: PartialAsyncConfig
+): Promise<string>
+
+/**
+ * Render a template
+ *
+ * If `template` is a string, Eta will compile it to a function and then call it with the provided data.
+ * If `template` is a template function, Eta will call it with the provided data.
+ *
+ * If `config.async` is `false`, Eta will return the rendered template.
+ *
+ * If `config.async` is `true` and there's a callback function, Eta will call the callback with `(err, renderedTemplate)`.
+ * If `config.async` is `true` and there's not a callback function, Eta will return a Promise that resolves to the rendered template.
+ *
+ * If `config.cache` is `true` and `config` has a `name` or `filename` property, Eta will cache the template on the first render and use the cached template for all subsequent renders.
+ *
+ * @param template Template string or template function
+ * @param data Data to render the template with
+ * @param config Optional config options
+ */
+export default function render(
+    template: string | TemplateFunction,
+    data: object,
+    config?: PartialConfig
+): string
+
+/**
+ * Render a template
+ *
+ * If `template` is a string, Eta will compile it to a function and then call it with the provided data.
+ * If `template` is a template function, Eta will call it with the provided data.
+ *
+ * If `config.async` is `false`, Eta will return the rendered template.
+ *
+ * If `config.async` is `true` and there's a callback function, Eta will call the callback with `(err, renderedTemplate)`.
+ * If `config.async` is `true` and there's not a callback function, Eta will return a Promise that resolves to the rendered template.
+ *
+ * If `config.cache` is `true` and `config` has a `name` or `filename` property, Eta will cache the template on the first render and use the cached template for all subsequent renders.
+ *
+ * @param template Template string or template function
+ * @param data Data to render the template with
+ * @param config Optional config options
+ * @param cb Callback function
+ */
+export default function render(
+    template: string | TemplateFunction,
+    data: object,
+    config?: PartialConfig,
+    cb?: CallbackFn
+): string | Promise<string> | void
 
 export default function render(
   template: string | TemplateFunction,
@@ -84,6 +161,46 @@ export default function render(
   }
 }
 
+/**
+ * Render a template asynchronously
+ *
+ * If `template` is a string, Eta will compile it to a function and call it with the provided data.
+ * If `template` is a function, Eta will call it with the provided data.
+ *
+ * If there is a callback function, Eta will call it with `(err, renderedTemplate)`.
+ * If there is not a callback function, Eta will return a Promise that resolves to the rendered template
+ *
+ * @param template Template string or template function
+ * @param data Data to render the template with
+ * @param config Optional config options
+ */
+export function renderAsync(
+    template: string | TemplateFunction,
+    data: object,
+    config?: PartialConfig
+): Promise<string>
+
+/**
+ * Render a template asynchronously
+ *
+ * If `template` is a string, Eta will compile it to a function and call it with the provided data.
+ * If `template` is a function, Eta will call it with the provided data.
+ *
+ * If there is a callback function, Eta will call it with `(err, renderedTemplate)`.
+ * If there is not a callback function, Eta will return a Promise that resolves to the rendered template
+ *
+ * @param template Template string or template function
+ * @param data Data to render the template with
+ * @param config Optional config options
+ * @param cb Callback function
+ */
+export function renderAsync(
+    template: string | TemplateFunction,
+    data: object,
+    config: PartialConfig,
+    cb: CallbackFn
+): void
+
 /**
  * Render a template asynchronously
  *
@@ -98,6 +215,12 @@ export default function render(
  * @param config Optional config options
  * @param cb Callback function
  */
+export function renderAsync(
+    template: string | TemplateFunction,
+    data: object,
+    config?: PartialConfig,
+    cb?: CallbackFn
+): string | Promise<string> | void
 
 export function renderAsync(
   template: string | TemplateFunction,