feat(nix): add flake support with automated vendorHash management

.github/workflows/update-vendor-hash.yml

@@ -0,0 +1,103 @@
+name: Update Vendor Hash
+
+on:
+  push:
+    branches: [ main ]
+    paths: 
+      - 'go.mod'
+      - 'go.sum'
+  workflow_dispatch:
+
+jobs:
+  update-vendor-hash:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+
+    - name: Install Nix
+      uses: cachix/install-nix-action@v24
+      with:
+        extra_nix_config: |
+          experimental-features = nix-command flakes
+
+    - name: Get current vendorHash from flake.nix
+      id: current-hash
+      run: |
+        current_hash=$(grep -o 'vendorHash = "sha256-[^"]*"' flake.nix | cut -d'"' -f2)
+        echo "current=$current_hash" >> $GITHUB_OUTPUT
+
+    - name: Calculate expected vendorHash
+      id: expected-hash
+      run: |
+        # Get the goModules derivation path
+        drv_path=$(nix eval --impure '.#packages.x86_64-linux.default.goModules.drvPath' 2>/dev/null | tr -d '"')
+
+        # Extract the hash from the derivation
+        hash=$(nix derivation show "$drv_path" | jq -r '.[] | .outputs.out.hash')
+
+        # Convert to SRI format
+        sri_hash=$(nix hash to-sri "sha256:$hash")
+
+        echo "expected=$sri_hash" >> $GITHUB_OUTPUT
+
+    - name: Check if update needed
+      id: check-update
+      run: |
+        if [ "${{ steps.current-hash.outputs.current }}" != "${{ steps.expected-hash.outputs.expected }}" ]; then
+          echo "update_needed=true" >> $GITHUB_OUTPUT
+          echo "Current hash: ${{ steps.current-hash.outputs.current }}"
+          echo "Expected hash: ${{ steps.expected-hash.outputs.expected }}"
+        else
+          echo "update_needed=false" >> $GITHUB_OUTPUT
+          echo "Vendor hash is up to date"
+        fi
+
+    - name: Update vendorHash
+      if: steps.check-update.outputs.update_needed == 'true'
+      run: |
+        sed -i 's/vendorHash = "sha256-[^"]*"/vendorHash = "${{ steps.expected-hash.outputs.expected }}"/' flake.nix
+
+    - name: Create Pull Request
+      if: steps.check-update.outputs.update_needed == 'true'
+      uses: peter-evans/create-pull-request@v5
+      with:
+        token: ${{ secrets.GITHUB_TOKEN }}
+        commit-message: "build(nix): update vendorHash to ${{ steps.expected-hash.outputs.expected }}"
+        title: "Update Nix vendorHash"
+        body: |
+          ## 🔄 Automated vendorHash Update
+
+          This PR updates the `vendorHash` in `flake.nix` to match the current Go module dependencies.
+
+          ### Changes
+          - **Previous hash**: `${{ steps.current-hash.outputs.current }}`
+          - **New hash**: `${{ steps.expected-hash.outputs.expected }}`
+
+          ### Trigger
+          This update was triggered by changes to Go module files (`go.mod` or `go.sum`).
+
+          ### Testing
+          The hash was calculated from the actual Go module dependencies and verified to build correctly.
+
+          ---
+          *This PR was created automatically by the `update-vendor-hash` workflow.*
+        branch: update-vendor-hash
+        branch-suffix: timestamp
+        delete-branch: true
+        labels: |
+          dependencies
+          automated
+          nix
+
+    - name: Build to verify
+      if: steps.check-update.outputs.update_needed == 'true'
+      run: |
+        echo "Building with updated hash to verify..."
+        nix build --impure
+        echo "✅ Build successful with updated vendorHash"

.github/workflows/verify-build.yml

@@ -0,0 +1,58 @@
+name: Verify Build
+
+on:
+  pull_request:
+    paths:
+      - 'flake.nix'
+      - 'go.mod'
+      - 'go.sum'
+      - '**.go'
+  push:
+    branches: [ main ]
+
+jobs:
+  verify-nix-build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Install Nix
+      uses: cachix/install-nix-action@v24
+      with:
+        extra_nix_config: |
+          experimental-features = nix-command flakes
+
+    - name: Verify flake
+      run: |
+        nix flake check --impure
+
+    - name: Build package
+      run: |
+        nix build --impure
+
+    - name: Test run
+      run: |
+        nix run --impure . -- --help
+
+    - name: Verify vendorHash is correct
+      run: |
+        # Get current hash from flake.nix
+        current_hash=$(grep -o 'vendorHash = "sha256-[^"]*"' flake.nix | cut -d'"' -f2)
+
+        # Calculate expected hash
+        drv_path=$(nix eval --impure '.#packages.x86_64-linux.default.goModules.drvPath' | tr -d '"')
+        expected_hash_raw=$(nix derivation show "$drv_path" | jq -r '.[] | .outputs.out.hash')
+        expected_hash=$(nix hash to-sri "sha256:$expected_hash_raw")
+
+        echo "Current vendorHash: $current_hash"
+        echo "Expected vendorHash: $expected_hash"
+
+        if [ "$current_hash" != "$expected_hash" ]; then
+          echo "❌ ERROR: vendorHash mismatch!"
+          echo "The vendorHash in flake.nix does not match the actual Go module dependencies."
+          echo "Please update the vendorHash or let the automation handle it."
+          exit 1
+        else
+          echo "✅ vendorHash is correct!"
+        fi

NIX_AUTOMATION.md

@@ -0,0 +1,90 @@
+# Nix Automation
+
+This project includes automated workflows to keep the Nix `vendorHash` up to date.
+
+## 🤖 Automated Workflows
+
+### 1. Update Vendor Hash (`.github/workflows/update-vendor-hash.yml`)
+
+**Triggers:**
+- Push to `main` branch with changes to `go.mod` or `go.sum`
+- Manual dispatch
+
+**What it does:**
+- Calculates the correct `vendorHash` from current Go dependencies
+- Compares with the hash in `flake.nix`
+- If different, creates a PR with the updated hash
+- Verifies the build works with the new hash
+
+### 2. Verify Build (`.github/workflows/verify-build.yml`)
+
+**Triggers:**
+- Pull requests affecting `flake.nix`, `go.mod`, `go.sum`, or Go files
+- Push to `main` branch
+
+**What it does:**
+- Runs `nix flake check`
+- Builds the package with `nix build`
+- Tests the binary with `nix run`
+- Verifies the `vendorHash` is correct
+
+## 🛠️ Local Development
+
+### Update vendorHash manually
+
+```bash
+./update-vendor-hash.sh
+```
+
+This script:
+- ✅ Checks if update is needed
+- 🔄 Updates `flake.nix` if hash differs
+- 🔨 Verifies build works
+- 📝 Shows current vs expected hash
+
+### Quick commands
+
+```bash
+# Build the package
+nix build --impure
+
+# Run the binary
+nix run --impure . -- --help
+
+# Enter development shell
+nix develop
+
+# Check flake
+nix flake check --impure
+```
+
+## 📋 How it works
+
+1. **Hash Calculation**: The correct `vendorHash` is calculated from the Go module dependencies without building
+2. **Smart Updates**: Only creates PRs when the hash actually needs updating
+3. **Verification**: All changes are verified to build successfully
+4. **Automation**: Runs automatically when Go dependencies change
+
+## 🔧 Manual Hash Update
+
+If you need to update the hash manually:
+
+```bash
+# Get the current hash
+current_hash=$(grep -o 'vendorHash = "sha256-[^"]*"' flake.nix | cut -d'"' -f2)
+
+# Calculate expected hash
+drv_path=$(nix eval --impure '.#packages.x86_64-linux.default.goModules.drvPath' | tr -d '"')
+expected_hash=$(nix derivation show "$drv_path" | jq -r '.[] | .outputs.out.hash' | xargs -I {} nix hash to-sri "sha256:{}")
+
+# Update flake.nix
+sed -i "s/vendorHash = \"sha256-[^\"]*\"/vendorHash = \"$expected_hash\"/" flake.nix
+```
+
+## 📈 Benefits
+
+- **Automated**: No manual intervention needed for hash updates
+- **Reliable**: Always uses the correct hash calculated from actual dependencies
+- **Fast**: Doesn't require failed builds to get the hash
+- **Verified**: All updates are tested before merging
+- **Transparent**: Clear PR descriptions explain what changed

README.md

@@ -15,17 +15,31 @@ This is an [MCP](https://modelcontextprotocol.io/introduction) server that runs
 
 ## Setup
 
+### Option 1: Using Go
+
 1. **Install Go**: Follow instructions at <https://golang.org/doc/install>
 2. **Install or update this server**: `go install github.com/isaacphi/mcp-language-server@latest`
 3. **Install a language server**: _follow one of the guides below_
 4. **Configure your MCP client**: _follow one of the guides below_
 
+### Option 2: Using Nix
+
+1. **Run directly with Nix**: `nix run github:isaacphi/mcp-language-server -- --workspace /path/to/your/project --lsp gopls`
+2. **Install a language server**: _follow one of the guides below_
+3. **Configure your MCP client**: _follow one of the guides below_
+
 <details>
   <summary>Go (gopls)</summary>
   <div>
-    <p><strong>Install gopls</strong>: <code>go install golang.org/x/tools/gopls@latest</code></p>
-    <p><strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\ Support/Claude/claude_desktop_config.json</code></p>
-
+    <p><strong>Install gopls</strong>:</p>
+    <ul>
+      <li><strong>Go</strong>: <code>go install golang.org/x/tools/gopls@latest</code></li>
+      <li><strong>Nix</strong>: <code>nix profile install nixpkgs#gopls</code> or use in shell</li>
+    </ul>
+
+    <p><strong>Configure your MCP client</strong>:</p>
+
+    <p><em>Using Go installation:</em></p>
 <pre>
 {
   "mcpServers": {
@@ -41,6 +55,25 @@ This is an [MCP](https://modelcontextprotocol.io/introduction) server that runs
     }
   }
 }
+</pre>
+
+    <p><em>Using Nix:</em></p>
+<pre>
+{
+  "mcpServers": {
+    "language-server": {
+      "command": "nix",
+      "args": [
+        "run", "github:isaacphi/mcp-language-server", "--",
+        "--workspace", "/Users/you/dev/yourproject/",
+        "--lsp", "gopls"
+      ],
+      "env": {
+        "PATH": "/nix/var/nix/profiles/default/bin:/run/current-system/sw/bin"
+      }
+    }
+  }
+}
 </pre>
 
 <p><strong>Note</strong>: Not all clients will need these environment variables. For Claude Desktop you will need to update the environment variables above based on your machine and username:</p>
@@ -77,9 +110,15 @@ This is an [MCP](https://modelcontextprotocol.io/introduction) server that runs
 <details>
   <summary>Python (pyright)</summary>
   <div>
-    <p><strong>Install pyright</strong>: <code>npm install -g pyright</code></p>
-    <p><strong>Configure your MCP client</strong>: This will be different but similar for each client. For Claude Desktop, add the following to <code>~/Library/Application\ Support/Claude/claude_desktop_config.json</code></p>
-
+    <p><strong>Install pyright</strong>:</p>
+    <ul>
+      <li><strong>npm</strong>: <code>npm install -g pyright</code></li>
+      <li><strong>Nix</strong>: <code>nix profile install nixpkgs#pyright</code> or use in shell</li>
+    </ul>
+
+    <p><strong>Configure your MCP client</strong>:</p>
+
+    <p><em>Using npm installation:</em></p>
 <pre>
 {
   "mcpServers": {
@@ -96,6 +135,23 @@ This is an [MCP](https://modelcontextprotocol.io/introduction) server that runs
     }
   }
 }
+</pre>
+
+    <p><em>Using Nix:</em></p>
+<pre>
+{
+  "mcpServers": {
+    "language-server": {
+      "command": "nix",
+      "args": [
+        "run", "github:isaacphi/mcp-language-server", "--",
+        "--workspace", "/Users/you/dev/yourproject/",
+        "--lsp", "pyright-langserver",
+        "--", "--stdio"
+      ]
+    }
+  }
+}
 </pre>
   </div>
 </details>
@@ -235,6 +291,32 @@ Configure your Claude Desktop (or similar) to use the local binary:
 
 Rebuild after making changes.
 
+## Nix Usage
+
+### Quick Start
+
+```bash
+# Run directly from GitHub
+nix run github:isaacphi/mcp-language-server -- --workspace /path/to/project --lsp gopls
+
+# Clone and run locally
+git clone https://github.com/isaacphi/mcp-language-server.git
+cd mcp-language-server
+nix run . -- --workspace /path/to/project --lsp gopls
+
+# Development shell with Go and tools
+nix develop
+```
+
+### Nix Flake
+
+This project includes a `flake.nix` with:
+- **`packages.default`**: The mcp-language-server binary
+- **`apps.default`**: Direct execution with `nix run`
+- **`devShells.default`**: Development environment with Go, just, and gopls
+
+The `vendorHash` is automatically maintained by GitHub Actions when Go dependencies change.
+
 ### Logging
 
 Setting the `LOG_LEVEL` environment variable to DEBUG enables verbose logging to stderr for all components including messages to and from the language server and the language server's logs.