add support for isArrayInsertion

Author: mbullington

src/impl/edit.ts

@@ -12,7 +12,7 @@ export function removeProperty(text: string, path: JSONPath, formattingOptions:
 	return setProperty(text, path, void 0, formattingOptions);
 }
 
-export function setProperty(text: string, originalPath: JSONPath, value: any, formattingOptions: FormattingOptions, getInsertionIndex?: (properties: string[]) => number): Edit[] {
+export function setProperty(text: string, originalPath: JSONPath, value: any, formattingOptions: FormattingOptions, getInsertionIndex?: (properties: string[]) => number, isArrayInsertion: boolean = false): Edit[] {
 	let path = originalPath.slice()
 	let errors: ParseError[] = [];
 	let root = parseTree(text, errors);
@@ -114,13 +114,25 @@ export function setProperty(text: string, originalPath: JSONPath, value: any, fo
 				edit = { offset: toRemove.offset, length: parent.children[removalIndex + 1].offset - toRemove.offset, content: '' };
 			}
 			return withFormatting(text, edit, formattingOptions);
-		} else if (value !== void 0 && parent.children.length > lastSegment) {
-			let modifyIndex = lastSegment;
-			let toModify = parent.children[modifyIndex];
-			let newProperty = `${JSON.stringify(value)}`;
-			return withFormatting(text, { offset: toModify.offset, length: toModify.length, content: newProperty }, formattingOptions);
+		} else if (value !== void 0) {
+			let edit: Edit;
+			const newProperty = `${JSON.stringify(value)}`;
+
+			if (!isArrayInsertion && parent.children.length > lastSegment) {
+				let toModify = parent.children[lastSegment];
+
+				edit = { offset: toModify.offset, length: toModify.length, content: newProperty }
+			} else if (parent.children.length === 0 || lastSegment === 0) {
+					edit = { offset: parent.offset + 1, length: 0, content: parent.children.length === 0 ? newProperty : newProperty + ',' };
+			} else {
+				const index = lastSegment > parent.children.length ? parent.children.length : lastSegment;
+				const previous = parent.children[index - 1];
+				edit = { offset: previous.offset + previous.length, length: 0, content: ',' + newProperty };
+			}
+
+			return withFormatting(text, edit, formattingOptions);
 		} else {
-			throw new Error(`Can not ${value === void 0 ? 'remove' : 'modify'} Array index ${insertIndex} as length is not sufficient`);
+			throw new Error(`Can not ${value === void 0 ? 'remove' : (isArrayInsertion ? 'insert' : 'modify')} Array index ${insertIndex} as length is not sufficient`);
 		}
 	} else {
 		throw new Error(`Can not add ${typeof lastSegment !== 'number' ? 'index' : 'property'} to parent of type ${parent.type}`);

src/main.ts

@@ -353,6 +353,11 @@ export interface ModificationOptions {
 	 * Formatting options
 	*/
 	formattingOptions: FormattingOptions;
+	/**
+	 * Default false. If `JSONPath` refers to an index of an array and {@property isArrayInsertion} is `true`, then
+	 * {@function modify} will insert a new item at that location instead of overwriting its contents.
+	 */
+	isArrayInsertion?: boolean;
 	/**
 	 * Optional function to define the insertion index given an existing list of properties.
 	 */
@@ -375,7 +380,7 @@ export interface ModificationOptions {
  * To apply edits to an input, you can use `applyEdits`.
  */
 export function modify(text: string, path: JSONPath, value: any, options: ModificationOptions): Edit[] {
-	return edit.setProperty(text, path, value, options.formattingOptions, options.getInsertionIndex);
+	return edit.setProperty(text, path, value, options.formattingOptions, options.getInsertionIndex, options.isArrayInsertion);
 }
 
 /**

src/test/edit.test.ts

@@ -133,22 +133,47 @@ suite('JSON - edits', () => {
 		edits = setProperty(content, ['x', 2], 4, formatterOptions);
 		assertEdit(content, edits, '{\n  "x": [1, 2, 4],\n  "y": 0\n}');
 
-		let message = "allowed setProperty to set array item outside of bounds";
-		try {
-			setProperty(content, ['x', 3], 3, formatterOptions)
-			throw new Error(message);
-		} catch(e) {
-			assert(e && e.message !== message);
-		}
+		edits = setProperty(content, ['x', 3], 3, formatterOptions)
+		assertEdit(content, edits, '{\n  "x": [\n    1,\n    2,\n    3,\n    3\n  ],\n  "y": 0\n}');
+	});
+
+	test('insert item at 0; isArrayInsertion = true', () => {
+		let content = '[\n  2,\n  3\n]';
+		let edits = setProperty(content, [0], 1, formatterOptions, undefined, true);
+		assertEdit(content, edits, '[\n  1,\n  2,\n  3\n]');
+	});
+
+	test('insert item at 0 in empty array', () => {
+		let content = '[\n]';
+		let edits = setProperty(content, [0], 1, formatterOptions);
+		assertEdit(content, edits, '[\n  1\n]');
+	});
+
+	test('insert item at an index; isArrayInsertion = true', () => {
+		let content = '[\n  1,\n  3\n]';
+		let edits = setProperty(content, [1], 2, formatterOptions, undefined, true);
+		assertEdit(content, edits, '[\n  1,\n  2,\n  3\n]');
+	});
+
+	test('insert item at an index in empty array', () => {
+		let content = '[\n]';
+		let edits = setProperty(content, [1], 1, formatterOptions);
+		assertEdit(content, edits, '[\n  1\n]');
+	});
+
+	test('insert item at end index', () => {
+		let content = '[\n  1,\n  2\n]';
+		let edits = setProperty(content, [2], 3, formatterOptions);
+		assertEdit(content, edits, '[\n  1,\n  2,\n  3\n]');
 	});
 
-	test('insert item to empty array', () => {
+	test('insert item at end to empty array', () => {
 		let content = '[\n]';
 		let edits = setProperty(content, [-1], 'bar', formatterOptions);
 		assertEdit(content, edits, '[\n  "bar"\n]');
 	});
 
-	test('insert item', () => {
+	test('insert item at end', () => {
 		let content = '[\n  1,\n  2\n]';
 		let edits = setProperty(content, [-1], 'bar', formatterOptions);
 		assertEdit(content, edits, '[\n  1,\n  2,\n  "bar"\n]');