fix: tags multiline, edit decorator position

src/frontmatter/frontmatterFields.test.ts

@@ -1,6 +1,6 @@
-import { describe, expect, it } from "vitest";
 import { TaskPriority } from "@/model/taskPriority";
 import { TaskStatus } from "@/model/taskStatus";
+import { describe, expect, it } from "vitest";
 import {
 	extractFrontmatterBlock,
 	findFieldRange,
@@ -20,6 +20,17 @@ tags: [old]
 Body
 `;
 
+const blockTagsSample = `---
+priority: medium
+tags:
+  - bug
+  - issue
+status: todo
+---
+
+Body
+`;
+
 describe("replaceFrontmatterField", () => {
 	it("replaces status value", () => {
 		const result = replaceFrontmatterField(sample, "status", TaskStatus.DONE);
@@ -41,6 +52,20 @@ describe("replaceFrontmatterField", () => {
 		expect(result.content).toContain("priority: critical");
 	});
 
+	it("replaces block-style tags without leaving leftover list items", () => {
+		const result = replaceFrontmatterField(
+			blockTagsSample,
+			"tags",
+			"\n  - bug\n  - issue\n  - new_issue",
+		);
+		expect(result.ok).toBe(true);
+		if (!result.ok) return;
+		expect(result.content).toContain(
+			"tags:\n  - bug\n  - issue\n  - new_issue",
+		);
+		expect(result.content).not.toContain("  - bug\n  - bug");
+	});
+
 	it("fails when field is missing", () => {
 		const result = replaceFrontmatterField(sample, "assignee", "me");
 		expect(result).toEqual({ ok: false, reason: "no-field" });
@@ -59,27 +84,74 @@ describe("findFieldRange", () => {
 		const line = sample.split("\n")[range!.startLine];
 		expect(line.slice(range!.startCol, range!.endCol)).toBe("todo");
 	});
+
+	it("returns range covering multi-line block-style tags value", () => {
+		const range = findFieldRange(blockTagsSample, "tags");
+		expect(range).toBeDefined();
+		expect(range!.startLine).toBe(2);
+		expect(range!.startCol).toBe(5);
+		expect(range!.endLine).toBe(4);
+		expect(range!.endCol).toBe(9);
+	});
+
+	it("range from findFieldRange replaces entire block value", () => {
+		const range = findFieldRange(blockTagsSample, "tags");
+		expect(range).toBeDefined();
+		const lines = blockTagsSample.split("\n");
+		// Replace the range with new block-style value
+		const before = lines.slice(0, range!.startLine);
+		const after = lines.slice(range!.endLine + 1);
+		const replaced = [...before, "tags:\n  - bug\n  - issue", ...after].join(
+			"\n",
+		);
+		expect(replaced).not.toMatch(/^- /m);
+	});
 });
 
 describe("formatTagsYamlValue", () => {
-	it("formats empty and simple lists", () => {
+	it("formats empty list as inline []", () => {
 		expect(formatTagsYamlValue([])).toBe("[]");
-		expect(formatTagsYamlValue(["bug", "frontend"])).toBe("[bug, frontend]");
 	});
 
-	it("quotes tags with spaces", () => {
-		expect(formatTagsYamlValue(["my tag"])).toBe('["my tag"]');
+	it("formats single tag as block-style list", () => {
+		expect(formatTagsYamlValue(["bug"])).toBe("\n  - bug");
+	});
+
+	it("formats multiple tags as block-style list", () => {
+		expect(formatTagsYamlValue(["bug", "frontend"])).toBe(
+			"\n  - bug\n  - frontend",
+		);
+	});
+
+	it("quotes tags with spaces in block-style", () => {
+		expect(formatTagsYamlValue(["my tag", "plain"])).toBe(
+			'\n  - "my tag"\n  - plain',
+		);
 	});
 });
 
 describe("setFrontmatterTags", () => {
-	it("replaces the tags line", () => {
+	it("replaces the tags line with block-style list", () => {
 		const result = setFrontmatterTags(sample, ["bug", "docs"]);
 		expect(result.ok).toBe(true);
 		if (!result.ok) return;
-		expect(result.content).toContain("tags: [bug, docs]");
+		expect(result.content).toContain("tags:\n  - bug\n  - docs");
 		expect(result.content).not.toContain("tags: [old]");
 	});
+
+	it("replaces block-style tags without leaving orphaned list items", () => {
+		const result = setFrontmatterTags(blockTagsSample, [
+			"bug",
+			"issue",
+			"new_issue",
+		]);
+		expect(result.ok).toBe(true);
+		if (!result.ok) return;
+		expect(result.content).toContain(
+			"tags:\n  - bug\n  - issue\n  - new_issue",
+		);
+		expect(result.content).not.toContain("  - bug\n  - bug");
+	});
 });
 
 describe("extractFrontmatterBlock", () => {

src/frontmatter/frontmatterFields.ts

@@ -93,11 +93,25 @@ export function findFieldRange(
 		}
 
 		if (valueText.length === 0) {
+			// Block-style value — extend to continuation lines
+			const keyIndent = indent.length;
+			let endLine = i;
+			let endCol = line.length;
+			for (let j = i + 1; j < block.closeLine; j += 1) {
+				const nextLine = lines[j] ?? "";
+				const nextIndent = nextLine.match(/^\s*/)?.[0].length ?? 0;
+				if (nextIndent > keyIndent) {
+					endLine = j;
+					endCol = nextLine.length;
+				} else {
+					break;
+				}
+			}
 			return {
 				startLine: i,
-				startCol: 0,
-				endLine: i,
-				endCol: line.length,
+				startCol: valueCol,
+				endLine,
+				endCol,
 			};
 		}
 
@@ -143,12 +157,12 @@ export type ReplaceFrontmatterFieldResult =
 	| { ok: true; content: string; range: TextRange }
 	| { ok: false; reason: "no-frontmatter" | "no-field" };
 
-/** Inline YAML list for frontmatter `tags: […]`. */
+/** Block-style YAML list for frontmatter `tags:\n  - item`. */
 export function formatTagsYamlValue(tags: string[]): string {
 	if (tags.length === 0) {
 		return "[]";
 	}
-	return `[${tags.map((t) => yamlInlineScalar(t)).join(", ")}]`;
+	return "\n" + tags.map((t) => `  - ${yamlInlineScalar(t)}`).join("\n");
 }
 
 export function setFrontmatterTags(
@@ -161,6 +175,7 @@ export function setFrontmatterTags(
 /**
  * Replace a scalar frontmatter field value on its line.
  * Does not re-serialize YAML; only rewrites the value after `:`.
+ * Handles multi-line block-style values (value starting with \n).
  */
 export function replaceFrontmatterField(
 	content: string,
@@ -178,6 +193,7 @@ export function replaceFrontmatterField(
 	}
 
 	const lines = content.split(/\r?\n/);
+	const eol = content.includes("\r\n") ? "\r\n" : "\n";
 	const line = lines[lineRange.startLine] ?? "";
 	const colonIndex = line.indexOf(":");
 	if (colonIndex < 0) {
@@ -185,11 +201,38 @@ export function replaceFrontmatterField(
 	}
 
 	const prefix = line.slice(0, colonIndex + 1);
-	const spacing = line.slice(colonIndex + 1).match(/^\s*/)?.[0] ?? " ";
-	const newLine = `${prefix}${spacing || " "}${value}`;
-	lines[lineRange.startLine] = newLine;
+	const keyIndent = line.match(/^\s*/)?.[0].length ?? 0;
+
+	if (value.startsWith("\n")) {
+		// Block-style value: replace key line and remove old continuation lines
+		lines[lineRange.startLine] = prefix;
+
+		// Find and remove old continuation lines
+		let continuationEnd = lineRange.startLine;
+		for (let j = lineRange.startLine + 1; j < block.closeLine; j += 1) {
+			const nextLine = lines[j] ?? "";
+			const nextIndent = nextLine.match(/^\s*/)?.[0].length ?? 0;
+			if (nextIndent > keyIndent) {
+				continuationEnd = j;
+			} else {
+				break;
+			}
+		}
+		const removeCount = continuationEnd - lineRange.startLine;
+		if (removeCount > 0) {
+			lines.splice(lineRange.startLine + 1, removeCount);
+		}
+
+		// Append the value lines (skip leading \n)
+		const valueLines = value.slice(1).split("\n");
+		for (let k = valueLines.length - 1; k >= 0; k -= 1) {
+			lines.splice(lineRange.startLine + 1, 0, valueLines[k]);
+		}
+	} else {
+		const spacing = line.slice(colonIndex + 1).match(/^\s*/)?.[0] ?? " ";
+		lines[lineRange.startLine] = `${prefix}${spacing || " "}${value}`;
+	}
 
-	const eol = content.includes("\r\n") ? "\r\n" : "\n";
 	const next = lines.join(eol);
 
 	const valueRange = findFieldRange(next, key);
@@ -200,7 +243,7 @@ export function replaceFrontmatterField(
 			startLine: lineRange.startLine,
 			startCol: 0,
 			endLine: lineRange.startLine,
-			endCol: newLine.length,
+			endCol: lines[lineRange.startLine].length,
 		},
 	};
 }

src/ui/taskDecorations.ts

@@ -118,12 +118,14 @@ export function registerTaskDecorations(
 
 		const tagsRange = findFieldRange(text, EditableField.TAGS);
 		if (tagsRange) {
+			const lines = text.split(/\r?\n/);
+			const lineEnd = lines[tagsRange.startLine]?.length ?? 0;
 			options.push({
 				range: new vscode.Range(
 					tagsRange.startLine,
-					tagsRange.startCol,
-					tagsRange.endLine,
-					tagsRange.endCol,
+					lineEnd,
+					tagsRange.startLine,
+					lineEnd,
 				),
 				hoverMessage: hoverTags(editor.document),
 				renderOptions: {