feat: Node.getStartLineNumber and SourceFile.getLineNumberFromPos.

src/compiler/common/Node.ts

@@ -742,6 +742,14 @@ export class Node<NodeType extends ts.Node = ts.Node> {
         return getPreviousMatchingPos(sourceFileText, this.getStart(includeJsDocComment), char => char === "\n");
     }
 
+    /**
+     * Gets the line number at the start of the node.
+     * @param includeJsDocComment - Whether to include the JS doc comment or not.
+     */
+    getStartLineNumber(includeJsDocComment?: boolean) {
+        return this.getSourceFile().getLineNumberFromPos(this.getStartLinePos(includeJsDocComment));
+    }
+
     /**
      * Gets if this is the first node on the current line.
      */

src/compiler/file/SourceFile.ts

@@ -95,6 +95,14 @@ export class SourceFile extends SourceFileBase<ts.SourceFile> {
         return FileUtils.getDirPath(this.compilerNode.fileName);
     }
 
+    /**
+     * Gets the line number of the provided position.
+     * @param pos - Position
+     */
+    getLineNumberFromPos(pos: number) {
+        return StringUtils.getLineNumberFromPos(this.getFullText(), pos);
+    }
+
     /**
      * Copy this source file to a new file.
      * @param filePath - A new file path. Can be relative to the original file or an absolute path.

src/tests/compiler/common/nodeTests.ts

@@ -316,6 +316,13 @@ describe(nameof(Node), () => {
         });
     });
 
+    describe(nameof<Node>(n => n.getStartLineNumber), () => {
+        it("should get the start line number of the node", () => {
+            const {firstChild} = getInfoFromText<ClassDeclaration>("\n\nclass MyClass {\n\n    prop: string;\n}");
+            expect(firstChild.getInstanceProperties()[0].getStartLineNumber()).to.equal(5);
+        });
+    });
+
     describe(nameof<Node>(n => n.getStart), () => {
         function doTest(text: string, expectedPos: number, includeJsDocComment?: boolean) {
             const {firstChild} = getInfoFromText(text);

src/tests/utils/stringUtilsTests.ts

@@ -0,0 +1,45 @@
+import {expect} from "chai";
+import * as errors from "./../../errors";
+import {StringUtils} from "./../../utils";
+
+describe(nameof(StringUtils), () => {
+    describe(nameof(StringUtils.getLineNumberFromPos), () => {
+        it("should throw if providing a negative pos", () => {
+            expect(() => StringUtils.getLineNumberFromPos("", -1)).to.throw(errors.ArgumentOutOfRangeError);
+        });
+
+        it("should not throw if providing a pos the length of the string", () => {
+            expect(() => StringUtils.getLineNumberFromPos("", 1)).to.not.throw();
+        });
+
+        it("should throw if providing a pos greater than the length + 1", () => {
+            expect(() => StringUtils.getLineNumberFromPos("", 2)).to.throw(errors.ArgumentOutOfRangeError);
+        });
+
+        function doTest(newLineType: string) {
+            let str = `testing${newLineType}this${newLineType}out`;
+            const pos = str.length;
+            str += `${newLineType}more and more${newLineType}and more`;
+            expect(StringUtils.getLineNumberFromPos(str, pos)).to.equal(3);
+        }
+
+        it("should get the line position for the specified pos when using \r newlines", () => {
+            doTest("\r");
+        });
+
+        it("should get the line position for the specified pos when using \n newlines", () => {
+            doTest("\n");
+        });
+
+        it("should get the line position for the specified pos when using \r\n newlines", () => {
+            doTest("\r\n");
+        });
+
+        it("should get the line position for the specified pos when right after the newline when mixing newlines", () => {
+            let str = "testing\r\nthis\nout\rmore\r\nandmore\n";
+            const pos = str.length;
+            str += "out\r\nmore and more";
+            expect(StringUtils.getLineNumberFromPos(str, pos)).to.equal(6);
+        });
+    });
+});

src/utils/StringUtils.ts

@@ -1,4 +1,6 @@
-export class StringUtils {
+import * as errors from "./../errors";
+
+export class StringUtils {
     private constructor() {
     }
 
@@ -20,4 +22,17 @@
     static endsWith(str: string, endsWithString: string) {
         return str.substr(str.length - endsWithString.length, endsWithString.length) === endsWithString;
     }
+
+    static getLineNumberFromPos(str: string, pos: number) {
+        errors.throwIfOutOfRange(pos, [0, str.length + 1], nameof(pos));
+        // do not allocate a string in this method
+        let count = 0;
+
+        for (let i = 0; i < pos; i++) {
+            if (str[i] === "\n" || (str[i] === "\r" && str[i + 1] !== "\n"))
+                count++;
+        }
+
+        return count + 1; // convert count to line number
+    }
 }