add startLine option (#346)

README.md

@@ -50,6 +50,8 @@ mind. When in doubt, use `.parse()`.
 
 - **sourceFilename**: Correlate output AST nodes with their source filename.  Useful when generating code and source maps from the ASTs of multiple input files.
 
+- **startLine**: By default, the first line of code parsed is treated as line 1. You can provide a line number to alternatively start with. Useful for integration with other source tools.
+
 - **plugins**: Array containing the plugins that you want to enable.
 
 - **strictMode**: TODO

src/options.js

@@ -4,6 +4,7 @@
 export const defaultOptions: {
   sourceType: string,
   sourceFilename: any,
+  startLine: number,
   allowReturnOutsideFunction: boolean,
   allowImportExportEverywhere: boolean,
   allowSuperOutsideMethod: boolean,
@@ -14,6 +15,9 @@ export const defaultOptions: {
   sourceType: "script",
   // Source filename.
   sourceFilename: undefined,
+  // Line from which to start counting source. Useful for
+  // integration with other tools.
+  startLine: 1,
   // When enabled, a return at the top level is not considered an
   // error.
   allowReturnOutsideFunction: false,

src/tokenizer/state.js

@@ -34,7 +34,7 @@ export default class State {
     this.commentStack     = [];
 
     this.pos = this.lineStart = 0;
-    this.curLine = 1;
+    this.curLine = options.startLine;
 
     this.type = tt.eof;
     this.value = null;

test/fixtures/core/categorized/startline-specified/actual.js

@@ -0,0 +1,2 @@
+call(1);
+run(2);