test(canvas/tabs): add tree.test.ts — 29 cases for FilesTab getIcon + buildTree

Covers:
- getIcon: directory icon, case-insensitive extension mapping (all FILE_ICONS keys),
  unknown extensions → default, dotfiles, double extensions (last segment wins)
- buildTree: empty, flat files, dirs-first sort, nested paths, duplicate dir guard,
  alphabetical sort within levels

Supports MR !708 fix to getIcon (case-insensitive extension lookup).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

canvas/src/components/tabs/FilesTab/tree.test.ts

@@ -0,0 +1,160 @@
+// @vitest-environment node
+/**
+ * FilesTab tree utilities — pure function coverage.
+ *
+ * Covers:
+ *   - getIcon: case-insensitive extension lookup, directory icons, unknown extensions
+ *   - buildTree: flat list → nested tree, dirs-first sorting, duplicate dir guard,
+ *     nested paths, single-level files
+ */
+import { describe, expect, it } from "vitest";
+
+import { buildTree, getIcon, type FileEntry } from "./tree";
+
+// ─── getIcon ────────────────────────────────────────────────────────────────────
+
+describe("getIcon — directory", () => {
+  it("returns folder icon for directories", () => {
+    expect(getIcon("src", true)).toBe("📁");
+    expect(getIcon("src/components", true)).toBe("📁");
+  });
+});
+
+describe("getIcon — extension mapping", () => {
+  const cases: [string, string][] = [
+    // Known extensions
+    ["script.py", "🐍"],
+    ["script.PY", "🐍"],           // case-insensitive
+    ["script.Py", "🐍"],
+    ["main.ts", "💠"],
+    ["main.TS", "💠"],
+    ["component.tsx", "💠"],
+    ["style.css", "🎨"],
+    ["index.html", "🌐"],
+    ["data.json", "{}"],
+    ["app.js", "📜"],
+    ["config.yaml", "⚙"],
+    ["config.yml", "⚙"],
+    ["README.md", "📄"],
+    ["build.sh", "▸"],
+    // Unknown extension → default
+    ["photo.png", "📄"],
+    ["archive.zip", "📄"],
+    ["document.pdf", "📄"],
+    ["data.xml", "📄"],
+  ];
+
+  it.each(cases)("getIcon('%s', false) === '%s'", (path, expected) => {
+    expect(getIcon(path, false)).toBe(expected);
+  });
+});
+
+describe("getIcon — edge cases", () => {
+  it("no extension (dotfile) falls back to default", () => {
+    expect(getIcon(".gitignore", false)).toBe("📄");
+    expect(getIcon(".env.local", false)).toBe("📄");
+  });
+
+  it("single-component path with no extension falls back to default", () => {
+    expect(getIcon("Makefile", false)).toBe("📄");
+  });
+
+  it("double extension takes last segment as extension", () => {
+    // "file.min.js" → ext = ".js" → 📜 (JS icon)
+    expect(getIcon("file.min.js", false)).toBe("📜");
+    // "app.d.ts" → ext = ".ts" → 💠 (TS icon)
+    expect(getIcon("app.d.ts", false)).toBe("💠");
+  });
+});
+
+// ─── buildTree ──────────────────────────────────────────────────────────────────
+
+describe("buildTree — empty input", () => {
+  it("returns empty array for empty input", () => {
+    expect(buildTree([])).toEqual([]);
+  });
+});
+
+describe("buildTree — flat files", () => {
+  it("puts files at root level", () => {
+    const files: FileEntry[] = [
+      { path: "a.txt", size: 10, dir: false },
+      { path: "b.txt", size: 20, dir: false },
+    ];
+    const tree = buildTree(files);
+    expect(tree).toHaveLength(2);
+    expect(tree[0]!.name).toBe("a.txt");
+    expect(tree[0]!.path).toBe("a.txt");
+    expect(tree[0]!.isDir).toBe(false);
+    expect(tree[0]!.size).toBe(10);
+  });
+
+  it("directories appear before files (dirs-first)", () => {
+    const files: FileEntry[] = [
+      { path: "b.txt", size: 10, dir: false },
+      { path: "src", size: 0, dir: true },
+      { path: "a.txt", size: 10, dir: false },
+    ];
+    const tree = buildTree(files);
+    expect(tree[0]!.isDir).toBe(true);
+    expect(tree[0]!.name).toBe("src");
+    expect(tree[1]!.name).toBe("a.txt");
+    expect(tree[2]!.name).toBe("b.txt");
+  });
+});
+
+describe("buildTree — nested paths", () => {
+  it("builds correct nested structure", () => {
+    const files: FileEntry[] = [
+      { path: "src", size: 0, dir: true },
+      { path: "src/app.tsx", size: 100, dir: false },
+      { path: "src/app.css", size: 50, dir: false },
+    ];
+    const tree = buildTree(files);
+    expect(tree).toHaveLength(1);
+    expect(tree[0]!.name).toBe("src");
+    expect(tree[0]!.isDir).toBe(true);
+    expect(tree[0]!.children).toHaveLength(2);
+    expect(tree[0]!.children[0]!.name).toBe("app.css");
+    expect(tree[0]!.children[1]!.name).toBe("app.tsx");
+  });
+
+  it("deeply nested paths build correct depth", () => {
+    const files: FileEntry[] = [
+      { path: "a", size: 0, dir: true },
+      { path: "a/b", size: 0, dir: true },
+      { path: "a/b/c.txt", size: 30, dir: false },
+    ];
+    const tree = buildTree(files);
+    expect(tree[0]!.name).toBe("a");
+    expect(tree[0]!.children[0]!.name).toBe("b");
+    expect(tree[0]!.children[0]!.children[0]!.name).toBe("c.txt");
+  });
+});
+
+describe("buildTree — duplicate dir guard", () => {
+  it("ignores duplicate directory entries", () => {
+    const files: FileEntry[] = [
+      { path: "src", size: 0, dir: true },
+      { path: "src", size: 0, dir: true },   // duplicate
+      { path: "src/app.ts", size: 10, dir: false },
+    ];
+    const tree = buildTree(files);
+    // Should only create src node once
+    const src = tree.find((n) => n.name === "src");
+    expect(src).toBeDefined();
+    expect(src!.children).toHaveLength(1);
+  });
+});
+
+describe("buildTree — alphabetical sort within same level", () => {
+  it("sorts alphabetically at each level", () => {
+    const files: FileEntry[] = [
+      { path: "zebra.txt", size: 1, dir: false },
+      { path: "apple.txt", size: 1, dir: false },
+      { path: "banana.txt", size: 1, dir: false },
+    ];
+    const tree = buildTree(files);
+    expect(tree.map((n) => n.name)).toEqual(["apple.txt", "banana.txt", "zebra.txt"]);
+  });
+});