feat: custom command aliases per guild (#166)

[BillChirico]

Summary

Closes #166

Allows guild admins to create custom aliases for bot commands (e.g. /w → /warn).

How it works

1. Discord registration — When an alias is created, it's registered as a guild-specific slash command with Discord so it appears in the command picker with auto-complete.
2. Persistent storage — Aliases are stored in the guild_command_aliases database table, scoped per guild.
3. In-memory cache — Loaded from DB on startup into a Map<guildId, Map<alias, target>>, giving O(1) resolution on every interaction.
4. Transparent routing — The interactionCreate handler resolves the alias to its target command before permission checks and execution. Permissions are evaluated against the target command, not the alias name.
5. Clean removal — Removing an alias deregisters the guild command from Discord and clears it from DB + cache.

Files changed

File	Purpose
migrations/004_command_aliases.cjs	New guild_command_aliases table with UNIQUE(guild_id, alias)
src/modules/commandAliases.js	Module: addAlias, removeAlias, listAliases, resolveAlias, loadAliasesFromDb
src/commands/alias.js	/alias add, /alias remove, /alias list slash command
src/index.js	Load aliases on startup; resolve in interactionCreate
tests/modules/commandAliases.test.js	13 tests for the module
tests/commands/alias.test.js	13 tests for the command

Usage

/alias add w warn          → Creates /w as an alias for /warn
/alias add b ban           → Creates /b as an alias for /ban
/alias list                → Shows all aliases for this server
/alias remove w            → Removes the /w alias

Test results

• ✅ 26 new tests passing (13 module + 13 command)
• ✅ Lint clean (biome, 2 pre-existing warnings unrelated to this PR)
• ✅ No regressions (3 pre-existing failures in redis/triage/ai-feedback on main, unchanged)

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📥 Commits

Reviewing files that changed from the base of the PR and between c6633d1 and e10cad3.

📒 Files selected for processing (6)

• migrations/004_command_aliases.cjs
• src/commands/alias.js
• src/index.js
• src/modules/commandAliases.js
• tests/commands/alias.test.js
• tests/modules/commandAliases.test.js

✨ Finishing Touches

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• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/issue-166

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[Copilot]

Pull request overview

Adds per-guild custom slash-command aliases so server admins can define shortcuts (e.g. /w → /warn) that show up in Discord’s command picker and route transparently to the target command at runtime.

Changes:

• Introduces guild_command_aliases persistence (migration) and an in-memory alias cache loaded at startup.
• Adds a new /alias admin command to add/remove/list aliases.
• Updates the interaction handler to resolve aliases before permission checks and command execution; adds module + command tests.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
migrations/004_command_aliases.cjs	Creates guild_command_aliases table and supporting index.
src/modules/commandAliases.js	Implements alias CRUD, Discord guild-command registration/deregistration, and cache loading/resolution.
src/commands/alias.js	Adds `/alias add
src/index.js	Loads aliases on startup; resolves aliases for slash-command execution.
tests/modules/commandAliases.test.js	Unit tests covering cache load/resolve/list and add/remove flows with mocked Discord REST + DB.
tests/commands/alias.test.js	Command-level tests for /alias subcommands and error handling paths.

---

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[greptile-apps]

Greptile Summary

Implemented per-guild command aliases with Discord slash command registration, PostgreSQL persistence, and in-memory caching for O(1) resolution. The architecture is sound with proper separation of concerns between the module, command, and integration layers.

Key implementation details:

• Aliases are registered as guild-specific Discord commands for autocomplete support
• Transparent routing resolves aliases before permission checks and command execution
• Permissions are correctly evaluated against target commands, not alias names
• Database uses parameterized queries throughout (no SQL injection risk)
• Comprehensive error handling with rollback mechanisms for failed operations
• 26 passing tests covering happy paths, validation, and error scenarios

Validation safeguards:

• Prevents shadowing built-in commands
• Blocks circular references (aliasing the /alias command)
• Prevents alias chaining (can't alias an alias)
• Discord command name format validation (1-32 chars, lowercase, alphanumeric + hyphens/underscores)

Minor observation:

• The ON CONFLICT DO UPDATE clause in addAlias may leave orphaned Discord commands in edge cases, though normal usage prevents this since Discord rejects duplicate command names

Confidence Score: 4/5

• Safe to merge with minimal risk - well-tested feature with proper security measures
• Score of 4 reflects solid implementation with comprehensive tests (26 new passing tests), proper security practices (parameterized queries, admin-only access, input validation), and thoughtful error handling. Minor deduction for edge case in ON CONFLICT handling that could theoretically leave orphaned Discord commands, though unlikely in practice.
• Pay attention to src/modules/commandAliases.js regarding the ON CONFLICT update behavior

Important Files Changed

Filename	Overview
src/modules/commandAliases.js	Core alias functionality with good error handling and rollback logic; ON CONFLICT clause may leave orphaned Discord commands if alias update is attempted
src/commands/alias.js	Well-implemented command with comprehensive validation, prevents shadowing built-in commands and circular alias references
src/index.js	Clean integration of alias resolution before permission checks, ensures permissions are evaluated against target command

Sequence Diagram

sequenceDiagram
    participant Admin
    participant Discord
    participant AliasCmd as /alias Command
    participant Module as commandAliases Module
    participant DB as PostgreSQL
    participant Cache as In-Memory Cache

    Note over Admin,Cache: Creating an Alias
    Admin->>Discord: /alias add w warn
    Discord->>AliasCmd: interaction
    AliasCmd->>AliasCmd: Validate alias name
    AliasCmd->>AliasCmd: Check no built-in conflict
    AliasCmd->>Module: addAlias(w → warn)
    Module->>Discord: POST guild command /w
    Discord-->>Module: command ID
    Module->>DB: INSERT with discord_command_id
    DB-->>Module: success
    Module->>Cache: Update cache
    Module-->>AliasCmd: {alias: w, target: warn}
    AliasCmd-->>Admin: ✅ Created alias

    Note over Admin,Cache: Using an Alias
    Admin->>Discord: /w @user reason
    Discord->>AliasCmd: interaction (commandName: w)
    AliasCmd->>Cache: resolveAlias(w)
    Cache-->>AliasCmd: warn
    AliasCmd->>AliasCmd: Check permissions for warn
    AliasCmd->>AliasCmd: Execute warn command
    AliasCmd-->>Admin: Warning issued

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_{Last reviewed commit: e10cad3}