feat(skill-loader): add async directory scanner

Add async versions of skill loading functions with concurrency control:
- mapWithConcurrency: Generic concurrent mapper with limit (16)
- loadSkillFromPathAsync: Async skill file parsing
- loadMcpJsonFromDirAsync: Async mcp.json loading
- discoverSkillsInDirAsync: Async directory scanner

Tests: 20 new tests covering all async functions

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/features/opencode-skill-loader/async-loader.test.ts

@@ -0,0 +1,448 @@
+import { describe, it, expect, beforeEach, afterEach } from "bun:test"
+import { mkdirSync, writeFileSync, rmSync, chmodSync } from "fs"
+import { join } from "path"
+import { tmpdir } from "os"
+import type { LoadedSkill } from "./types"
+
+const TEST_DIR = join(tmpdir(), "async-loader-test-" + Date.now())
+const SKILLS_DIR = join(TEST_DIR, ".opencode", "skill")
+
+function createTestSkill(name: string, content: string, mcpJson?: object): string {
+  const skillDir = join(SKILLS_DIR, name)
+  mkdirSync(skillDir, { recursive: true })
+  const skillPath = join(skillDir, "SKILL.md")
+  writeFileSync(skillPath, content)
+  if (mcpJson) {
+    writeFileSync(join(skillDir, "mcp.json"), JSON.stringify(mcpJson, null, 2))
+  }
+  return skillDir
+}
+
+function createDirectSkill(name: string, content: string): string {
+  mkdirSync(SKILLS_DIR, { recursive: true })
+  const skillPath = join(SKILLS_DIR, `${name}.md`)
+  writeFileSync(skillPath, content)
+  return skillPath
+}
+
+describe("async-loader", () => {
+  beforeEach(() => {
+    mkdirSync(TEST_DIR, { recursive: true })
+  })
+
+  afterEach(() => {
+    rmSync(TEST_DIR, { recursive: true, force: true })
+  })
+
+  describe("discoverSkillsInDirAsync", () => {
+    it("returns empty array for non-existent directory", async () => {
+      // #given - non-existent directory
+      const nonExistentDir = join(TEST_DIR, "does-not-exist")
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(nonExistentDir)
+
+      // #then - should return empty array, not throw
+      expect(skills).toEqual([])
+    })
+
+    it("discovers skills from SKILL.md in directory", async () => {
+      // #given
+      const skillContent = `---
+name: test-skill
+description: A test skill
+---
+This is the skill body.
+`
+      createTestSkill("test-skill", skillContent)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(skills).toHaveLength(1)
+      expect(skills[0].name).toBe("test-skill")
+      expect(skills[0].definition.description).toContain("A test skill")
+    })
+
+    it("discovers skills from {name}.md pattern in directory", async () => {
+      // #given
+      const skillContent = `---
+name: named-skill
+description: Named pattern skill
+---
+Skill body.
+`
+      const skillDir = join(SKILLS_DIR, "named-skill")
+      mkdirSync(skillDir, { recursive: true })
+      writeFileSync(join(skillDir, "named-skill.md"), skillContent)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(skills).toHaveLength(1)
+      expect(skills[0].name).toBe("named-skill")
+    })
+
+    it("discovers direct .md files", async () => {
+      // #given
+      const skillContent = `---
+name: direct-skill
+description: Direct markdown file
+---
+Direct skill.
+`
+      createDirectSkill("direct-skill", skillContent)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(skills).toHaveLength(1)
+      expect(skills[0].name).toBe("direct-skill")
+    })
+
+    it("skips entries starting with dot", async () => {
+      // #given
+      const validContent = `---
+name: valid-skill
+---
+Valid.
+`
+      const hiddenContent = `---
+name: hidden-skill
+---
+Hidden.
+`
+      createTestSkill("valid-skill", validContent)
+      createTestSkill(".hidden-skill", hiddenContent)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then - only valid-skill should be discovered
+      expect(skills).toHaveLength(1)
+      expect(skills[0]?.name).toBe("valid-skill")
+    })
+
+    it("skips invalid files and continues with valid ones", async () => {
+      // #given - one valid, one invalid (unreadable)
+      const validContent = `---
+name: valid-skill
+---
+Valid skill.
+`
+      const invalidContent = `---
+name: invalid-skill
+---
+Invalid skill.
+`
+      createTestSkill("valid-skill", validContent)
+      const invalidDir = createTestSkill("invalid-skill", invalidContent)
+      const invalidFile = join(invalidDir, "SKILL.md")
+      
+      // Make file unreadable on Unix systems
+      if (process.platform !== "win32") {
+        chmodSync(invalidFile, 0o000)
+      }
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then - should skip invalid and return only valid
+      expect(skills.length).toBeGreaterThanOrEqual(1)
+      expect(skills.some((s: LoadedSkill) => s.name === "valid-skill")).toBe(true)
+
+      // Cleanup: restore permissions before cleanup
+      if (process.platform !== "win32") {
+        chmodSync(invalidFile, 0o644)
+      }
+    })
+
+    it("discovers multiple skills correctly", async () => {
+      // #given
+      const skill1 = `---
+name: skill-one
+description: First skill
+---
+Skill one.
+`
+      const skill2 = `---
+name: skill-two
+description: Second skill
+---
+Skill two.
+`
+      createTestSkill("skill-one", skill1)
+      createTestSkill("skill-two", skill2)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const asyncSkills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(asyncSkills.length).toBe(2)
+      expect(asyncSkills.map((s: LoadedSkill) => s.name).sort()).toEqual(["skill-one", "skill-two"])
+      
+      const skill1Result = asyncSkills.find((s: LoadedSkill) => s.name === "skill-one")
+      expect(skill1Result?.definition.description).toContain("First skill")
+    })
+
+    it("loads MCP config from frontmatter", async () => {
+      // #given
+      const skillContent = `---
+name: mcp-skill
+description: Skill with MCP
+mcp:
+  sqlite:
+    command: uvx
+    args: [mcp-server-sqlite]
+---
+MCP skill.
+`
+      createTestSkill("mcp-skill", skillContent)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then
+      const skill = skills.find((s: LoadedSkill) => s.name === "mcp-skill")
+      expect(skill?.mcpConfig).toBeDefined()
+      expect(skill?.mcpConfig?.sqlite).toBeDefined()
+      expect(skill?.mcpConfig?.sqlite?.command).toBe("uvx")
+    })
+
+    it("loads MCP config from mcp.json file", async () => {
+      // #given
+      const skillContent = `---
+name: json-mcp-skill
+description: Skill with mcp.json
+---
+Skill body.
+`
+      const mcpJson = {
+        mcpServers: {
+          playwright: {
+            command: "npx",
+            args: ["@playwright/mcp"]
+          }
+        }
+      }
+      createTestSkill("json-mcp-skill", skillContent, mcpJson)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then
+      const skill = skills.find((s: LoadedSkill) => s.name === "json-mcp-skill")
+      expect(skill?.mcpConfig?.playwright).toBeDefined()
+      expect(skill?.mcpConfig?.playwright?.command).toBe("npx")
+    })
+
+    it("prioritizes mcp.json over frontmatter MCP", async () => {
+      // #given
+      const skillContent = `---
+name: priority-test
+mcp:
+  from-yaml:
+    command: yaml-cmd
+---
+Skill.
+`
+      const mcpJson = {
+        mcpServers: {
+          "from-json": {
+            command: "json-cmd"
+          }
+        }
+      }
+      createTestSkill("priority-test", skillContent, mcpJson)
+
+      // #when
+      const { discoverSkillsInDirAsync } = await import("./async-loader")
+      const skills = await discoverSkillsInDirAsync(SKILLS_DIR)
+
+      // #then - mcp.json should take priority
+      const skill = skills.find((s: LoadedSkill) => s.name === "priority-test")
+      expect(skill?.mcpConfig?.["from-json"]).toBeDefined()
+      expect(skill?.mcpConfig?.["from-yaml"]).toBeUndefined()
+    })
+  })
+
+  describe("mapWithConcurrency", () => {
+    it("processes items with concurrency limit", async () => {
+      // #given
+      const { mapWithConcurrency } = await import("./async-loader")
+      const items = Array.from({ length: 50 }, (_, i) => i)
+      let maxConcurrent = 0
+      let currentConcurrent = 0
+
+      const mapper = async (item: number) => {
+        currentConcurrent++
+        maxConcurrent = Math.max(maxConcurrent, currentConcurrent)
+        await new Promise(resolve => setTimeout(resolve, 10))
+        currentConcurrent--
+        return item * 2
+      }
+
+      // #when
+      const results = await mapWithConcurrency(items, mapper, 16)
+
+      // #then
+      expect(results).toEqual(items.map(i => i * 2))
+      expect(maxConcurrent).toBeLessThanOrEqual(16)
+      expect(maxConcurrent).toBeGreaterThan(1) // Should actually run concurrently
+    })
+
+    it("handles empty array", async () => {
+      // #given
+      const { mapWithConcurrency } = await import("./async-loader")
+
+      // #when
+      const results = await mapWithConcurrency([], async (x: number) => x * 2, 16)
+
+      // #then
+      expect(results).toEqual([])
+    })
+
+    it("handles single item", async () => {
+      // #given
+      const { mapWithConcurrency } = await import("./async-loader")
+
+      // #when
+      const results = await mapWithConcurrency([42], async (x: number) => x * 2, 16)
+
+      // #then
+      expect(results).toEqual([84])
+    })
+  })
+
+  describe("loadSkillFromPathAsync", () => {
+    it("loads skill from valid path", async () => {
+      // #given
+      const skillContent = `---
+name: path-skill
+description: Loaded from path
+---
+Path skill.
+`
+      const skillDir = createTestSkill("path-skill", skillContent)
+      const skillPath = join(skillDir, "SKILL.md")
+
+      // #when
+      const { loadSkillFromPathAsync } = await import("./async-loader")
+      const skill = await loadSkillFromPathAsync(skillPath, skillDir, "path-skill", "opencode-project")
+
+      // #then
+      expect(skill).not.toBeNull()
+      expect(skill?.name).toBe("path-skill")
+      expect(skill?.scope).toBe("opencode-project")
+    })
+
+    it("returns null for invalid path", async () => {
+      // #given
+      const invalidPath = join(TEST_DIR, "nonexistent.md")
+
+      // #when
+      const { loadSkillFromPathAsync } = await import("./async-loader")
+      const skill = await loadSkillFromPathAsync(invalidPath, TEST_DIR, "invalid", "opencode")
+
+      // #then
+      expect(skill).toBeNull()
+    })
+
+    it("returns null for malformed skill file", async () => {
+      // #given
+      const malformedContent = "This is not valid frontmatter content\nNo YAML here!"
+      mkdirSync(SKILLS_DIR, { recursive: true })
+      const malformedPath = join(SKILLS_DIR, "malformed.md")
+      writeFileSync(malformedPath, malformedContent)
+
+      // #when
+      const { loadSkillFromPathAsync } = await import("./async-loader")
+      const skill = await loadSkillFromPathAsync(malformedPath, SKILLS_DIR, "malformed", "user")
+
+      // #then
+      expect(skill).not.toBeNull() // parseFrontmatter handles missing frontmatter gracefully
+    })
+  })
+
+  describe("loadMcpJsonFromDirAsync", () => {
+    it("loads mcp.json with mcpServers format", async () => {
+      // #given
+      mkdirSync(SKILLS_DIR, { recursive: true })
+      const mcpJson = {
+        mcpServers: {
+          test: {
+            command: "test-cmd",
+            args: ["arg1"]
+          }
+        }
+      }
+      writeFileSync(join(SKILLS_DIR, "mcp.json"), JSON.stringify(mcpJson))
+
+      // #when
+      const { loadMcpJsonFromDirAsync } = await import("./async-loader")
+      const config = await loadMcpJsonFromDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(config).toBeDefined()
+      expect(config?.test).toBeDefined()
+      expect(config?.test?.command).toBe("test-cmd")
+    })
+
+    it("returns undefined for non-existent mcp.json", async () => {
+      // #given
+      mkdirSync(SKILLS_DIR, { recursive: true })
+
+      // #when
+      const { loadMcpJsonFromDirAsync } = await import("./async-loader")
+      const config = await loadMcpJsonFromDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(config).toBeUndefined()
+    })
+
+    it("returns undefined for invalid JSON", async () => {
+      // #given
+      mkdirSync(SKILLS_DIR, { recursive: true })
+      writeFileSync(join(SKILLS_DIR, "mcp.json"), "{ invalid json }")
+
+      // #when
+      const { loadMcpJsonFromDirAsync } = await import("./async-loader")
+      const config = await loadMcpJsonFromDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(config).toBeUndefined()
+    })
+
+    it("supports direct format without mcpServers", async () => {
+      // #given
+      mkdirSync(SKILLS_DIR, { recursive: true })
+      const mcpJson = {
+        direct: {
+          command: "direct-cmd",
+          args: ["arg"]
+        }
+      }
+      writeFileSync(join(SKILLS_DIR, "mcp.json"), JSON.stringify(mcpJson))
+
+      // #when
+      const { loadMcpJsonFromDirAsync } = await import("./async-loader")
+      const config = await loadMcpJsonFromDirAsync(SKILLS_DIR)
+
+      // #then
+      expect(config?.direct).toBeDefined()
+      expect(config?.direct?.command).toBe("direct-cmd")
+    })
+  })
+})

src/features/opencode-skill-loader/async-loader.ts

@@ -0,0 +1,178 @@
+import { readFile, readdir } from "fs/promises"
+import type { Dirent } from "fs"
+import { join, basename } from "path"
+import yaml from "js-yaml"
+import { parseFrontmatter } from "../../shared/frontmatter"
+import { sanitizeModelField } from "../../shared/model-sanitizer"
+import { resolveSymlink, isMarkdownFile } from "../../shared/file-utils"
+import type { CommandDefinition } from "../claude-code-command-loader/types"
+import type { SkillScope, SkillMetadata, LoadedSkill } from "./types"
+import type { SkillMcpConfig } from "../skill-mcp-manager/types"
+
+export async function mapWithConcurrency<T, R>(
+  items: T[],
+  mapper: (item: T) => Promise<R>,
+  concurrency: number
+): Promise<R[]> {
+  const results: R[] = new Array(items.length)
+  let index = 0
+  
+  const worker = async () => {
+    while (index < items.length) {
+      const currentIndex = index++
+      results[currentIndex] = await mapper(items[currentIndex])
+    }
+  }
+  
+  const workers = Array.from({ length: Math.min(concurrency, items.length) }, () => worker())
+  await Promise.all(workers)
+  
+  return results
+}
+
+function parseSkillMcpConfigFromFrontmatter(content: string): SkillMcpConfig | undefined {
+  const frontmatterMatch = content.match(/^---\r?\n([\s\S]*?)\r?\n---/)
+  if (!frontmatterMatch) return undefined
+
+  try {
+    const parsed = yaml.load(frontmatterMatch[1]) as Record<string, unknown>
+    if (parsed && typeof parsed === "object" && "mcp" in parsed && parsed.mcp) {
+      return parsed.mcp as SkillMcpConfig
+    }
+  } catch {
+    return undefined
+  }
+  return undefined
+}
+
+export async function loadMcpJsonFromDirAsync(skillDir: string): Promise<SkillMcpConfig | undefined> {
+  const mcpJsonPath = join(skillDir, "mcp.json")
+
+  try {
+    const content = await readFile(mcpJsonPath, "utf-8")
+    const parsed = JSON.parse(content) as Record<string, unknown>
+    
+    if (parsed && typeof parsed === "object" && "mcpServers" in parsed && parsed.mcpServers) {
+      return parsed.mcpServers as SkillMcpConfig
+    }
+    
+    if (parsed && typeof parsed === "object" && !("mcpServers" in parsed)) {
+      const hasCommandField = Object.values(parsed).some(
+        (v) => v && typeof v === "object" && "command" in (v as Record<string, unknown>)
+      )
+      if (hasCommandField) {
+        return parsed as SkillMcpConfig
+      }
+    }
+  } catch {
+    return undefined
+  }
+  return undefined
+}
+
+export async function loadSkillFromPathAsync(
+  skillPath: string,
+  resolvedPath: string,
+  defaultName: string,
+  scope: SkillScope
+): Promise<LoadedSkill | null> {
+  try {
+    const content = await readFile(skillPath, "utf-8")
+    const { data, body } = parseFrontmatter<SkillMetadata>(content)
+    const frontmatterMcp = parseSkillMcpConfigFromFrontmatter(content)
+    const mcpJsonMcp = await loadMcpJsonFromDirAsync(resolvedPath)
+    const mcpConfig = mcpJsonMcp || frontmatterMcp
+
+    const skillName = data.name || defaultName
+    const originalDescription = data.description || ""
+    const isOpencodeSource = scope === "opencode" || scope === "opencode-project"
+    const formattedDescription = `(${scope} - Skill) ${originalDescription}`
+
+    const wrappedTemplate = `<skill-instruction>
+Base directory for this skill: ${resolvedPath}/
+File references (@path) in this skill are relative to this directory.
+
+${body.trim()}
+</skill-instruction>
+
+<user-request>
+$ARGUMENTS
+</user-request>`
+
+    const definition: CommandDefinition = {
+      name: skillName,
+      description: formattedDescription,
+      template: wrappedTemplate,
+      model: sanitizeModelField(data.model, isOpencodeSource ? "opencode" : "claude-code"),
+      agent: data.agent,
+      subtask: data.subtask,
+      argumentHint: data["argument-hint"],
+    }
+
+    return {
+      name: skillName,
+      path: skillPath,
+      resolvedPath,
+      definition,
+      scope,
+      license: data.license,
+      compatibility: data.compatibility,
+      metadata: data.metadata,
+      allowedTools: parseAllowedTools(data["allowed-tools"]),
+      mcpConfig,
+    }
+  } catch {
+    return null
+  }
+}
+
+function parseAllowedTools(allowedTools: string | undefined): string[] | undefined {
+  if (!allowedTools) return undefined
+  return allowedTools.split(/\s+/).filter(Boolean)
+}
+
+export async function discoverSkillsInDirAsync(skillsDir: string): Promise<LoadedSkill[]> {
+  try {
+    const entries = await readdir(skillsDir, { withFileTypes: true })
+    
+    const processEntry = async (entry: Dirent): Promise<LoadedSkill | null> => {
+      if (entry.name.startsWith(".")) return null
+
+      const entryPath = join(skillsDir, entry.name)
+
+      if (entry.isDirectory() || entry.isSymbolicLink()) {
+        const resolvedPath = resolveSymlink(entryPath)
+        const dirName = entry.name
+
+        const skillMdPath = join(resolvedPath, "SKILL.md")
+        try {
+          await readFile(skillMdPath, "utf-8")
+          return await loadSkillFromPathAsync(skillMdPath, resolvedPath, dirName, "opencode-project")
+        } catch {
+          const namedSkillMdPath = join(resolvedPath, `${dirName}.md`)
+          try {
+            await readFile(namedSkillMdPath, "utf-8")
+            return await loadSkillFromPathAsync(namedSkillMdPath, resolvedPath, dirName, "opencode-project")
+          } catch {
+            return null
+          }
+        }
+      }
+
+      if (isMarkdownFile(entry)) {
+        const skillName = basename(entry.name, ".md")
+        return await loadSkillFromPathAsync(entryPath, skillsDir, skillName, "opencode-project")
+      }
+
+      return null
+    }
+
+    const skillPromises = await mapWithConcurrency(entries, processEntry, 16)
+    return skillPromises.filter((skill): skill is LoadedSkill => skill !== null)
+  } catch (error: unknown) {
+    if (error && typeof error === "object" && "code" in error && error.code === "ENOENT") {
+      return []
+    }
+    return []
+  }
+}