Implement error recovery

Closes parcel-bundler#39. Closes parcel-bundler#209.

Author: devongovett

examples/serialize.rs

@@ -9,7 +9,14 @@ fn parse() {
 
   let args: Vec<String> = env::args().collect();
   let contents = fs::read_to_string(&args[1]).unwrap();
-  let stylesheet = StyleSheet::parse(&args[1], &contents, ParserOptions::default()).unwrap();
+  let stylesheet = StyleSheet::parse(
+    &contents,
+    ParserOptions {
+      filename: args[1].clone(),
+      ..ParserOptions::default()
+    },
+  )
+  .unwrap();
   let json = serde_json::to_string(&stylesheet).unwrap();
   println!("{}", json);
 }

node/index.d.ts

@@ -34,7 +34,13 @@ export interface TransformOptions {
    * to be unused. These will be removed during minification. Note that these are not
    * selectors but individual names (without any . or # prefixes).
    */
-  unusedSymbols?: string[]
+  unusedSymbols?: string[],
+  /**
+   * Whether to ignore invalid rules and declarations rather than erroring.
+   * When enabled, warnings are returned, and the invalid rule or declaration is
+   * omitted from the output code.
+   */
+  errorRecovery?: boolean
 }
 
 export type BundleOptions = Omit<TransformOptions, 'code'>;
@@ -64,7 +70,16 @@ export interface TransformResult {
   /** CSS module references, if `dashedIdents` is enabled. */
   references: CSSModuleReferences,
   /** `@import` and `url()` dependencies, if enabled. */
-  dependencies: Dependency[] | void
+  dependencies: Dependency[] | void,
+  /** Warnings that occurred during compilation. */
+  warnings: Warning[]
+}
+
+export interface Warning {
+  message: string,
+  type: string,
+  value?: any,
+  loc: ErrorLocation
 }
 
 export interface CSSModulesConfig {
@@ -155,6 +170,10 @@ export interface Location {
   column: number
 }
 
+export interface ErrorLocation extends Location {
+  filename: string
+}
+
 /**
  * Compiles a CSS file, including optionally minifying and lowering syntax to the given
  * targets. A source map may also be generated, but this is not enabled by default.