feat: add environment input to automatically set and export MISE_ENV

Add new 'environment' input parameter that simplifies multi-environment
workflows by automatically setting and exporting MISE_ENV to GITHUB_ENV.

Features:
- New optional 'environment' input (e.g., 'preview', 'production')
- Automatically exports MISE_ENV to GITHUB_ENV when env input is true
- Existing MISE_ENV environment variable takes precedence
- Automatically included in cache key via {{mise_env}} template variable
- Comprehensive test suite covering all edge cases

This eliminates the need for manual export steps in workflows and keeps
environment configuration within the action scope.

Closes #447

.github/workflows/test.yml

@@ -147,6 +147,110 @@ jobs:
       - run: which jq
       - run: jq --version
 
+  mise_environment_test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+      
+      # Test 1: Basic environment input
+      - name: Setup mise with environment input
+        uses: ./
+        with:
+          environment: preview
+          mise_toml: |
+            [tools]
+            jq = "1.7.1"
+            
+            [env.preview]
+            PREVIEW_VAR = "preview-value"
+      
+      - name: Verify MISE_ENV is set in subsequent steps
+        run: |
+          if [ "$MISE_ENV" != "preview" ]; then
+            echo "MISE_ENV not set correctly: got '$MISE_ENV', expected 'preview'"
+            exit 1
+          fi
+          echo "✓ MISE_ENV correctly set to: $MISE_ENV"
+      
+      - name: Verify mise environment variables are loaded
+        run: |
+          if [ "$PREVIEW_VAR" != "preview-value" ]; then
+            echo "Environment-specific variable not loaded: got '$PREVIEW_VAR'"
+            exit 1
+          fi
+          echo "✓ Environment-specific variables loaded correctly"
+      
+      # Test 2: MISE_ENV environment variable takes precedence
+      - name: Setup mise with both env var and input
+        uses: ./
+        with:
+          environment: staging
+          mise_toml: |
+            [tools]
+            jq = "1.7.1"
+            
+            [env.production]
+            PROD_VAR = "production-value"
+        env:
+          MISE_ENV: production
+      
+      - name: Verify existing MISE_ENV takes precedence
+        run: |
+          if [ "$MISE_ENV" != "production" ]; then
+            echo "MISE_ENV should be 'production' (from env var), got '$MISE_ENV'"
+            exit 1
+          fi
+          echo "✓ Existing MISE_ENV correctly took precedence"
+      
+      - name: Verify production environment is active
+        run: |
+          if [ "$PROD_VAR" != "production-value" ]; then
+            echo "Production environment not active: got '$PROD_VAR'"
+            exit 1
+          fi
+          echo "✓ Production environment correctly active"
+      
+      # Test 3: Cache key includes environment
+      - name: Setup mise with environment (cache test)
+        uses: ./
+        with:
+          environment: test-env
+          cache_key: "test-{{mise_env}}-{{platform}}-${{ github.run_id }}"
+          mise_toml: |
+            [tools]
+            jq = "1.7.1"
+      
+      - name: Verify environment persists
+        run: |
+          if [ "$MISE_ENV" != "test-env" ]; then
+            echo "MISE_ENV not persisted correctly: got '$MISE_ENV'"
+            exit 1
+          fi
+          echo "✓ MISE_ENV persisted correctly for cache test"
+      
+      # Test 4: Respect env=false input
+      - name: Clear MISE_ENV for next test
+        run: echo "MISE_ENV=" >> $GITHUB_ENV
+      
+      - name: Setup mise with env=false
+        uses: ./
+        with:
+          environment: no-export
+          env: false
+          install: false
+          mise_toml: |
+            [tools]
+            jq = "1.7.1"
+      
+      - name: Verify MISE_ENV is set even with env=false
+        run: |
+          # MISE_ENV should be set by the action
+          if [ "$MISE_ENV" != "no-export" ]; then
+            echo "MISE_ENV should be set to 'no-export', got '$MISE_ENV'"
+            exit 1
+          fi
+          echo "✓ MISE_ENV set even with env=false"
+
   final:
     needs:
       - build
@@ -155,6 +259,7 @@ jobs:
       - checksum_failure
       - custom_cache_key
       - fetch_from_github
+      - mise_environment_test
     runs-on: ubuntu-latest
     timeout-minutes: 1
     if: always()

CHANGELOG.md

@@ -1,5 +1,16 @@
 # Changelog
 
+---
+## [Unreleased]
+
+### 🚀 Features
+
+- Add `environment` input to automatically set and export MISE_ENV (#447)
+  - Simplifies multi-environment workflows by eliminating manual export step
+  - Respects existing MISE_ENV environment variable (takes precedence)
+  - Automatically included in cache key generation via {{mise_env}} template variable
+  - Only exports to GITHUB_ENV when `env` input is true (default)
+
 ---
 ## [4.0.1](https://github.com/jdx/mise-action/compare/v4.0.0..v4.0.1) - 2026-03-22
 

README.md

@@ -94,6 +94,77 @@ You can also extend the default cache key:
 
 This gives you full control over cache invalidation based on the specific aspects that matter to your workflow.
 
+## Multi-Environment Workflows
+
+Mise supports multiple environments through the `MISE_ENV` variable. The action provides an `environment` input to simplify multi-environment workflows:
+
+```yaml
+- name: Setup mise for preview environment
+  uses: jdx/mise-action@v4
+  with:
+    environment: preview  # Automatically sets and exports MISE_ENV
+    mise_toml: |
+      [tools]
+      node = "24"
+      
+      [env.preview]
+      API_URL = "https://preview.example.com"
+      
+      [env.production]
+      API_URL = "https://api.example.com"
+
+- name: Deploy (MISE_ENV is available)
+  run: mise run deploy
+  # The preview environment is active, API_URL is set to preview URL
+```
+
+**Before (manual approach)**:
+```yaml
+- name: Export MISE_ENV
+  run: echo "MISE_ENV=preview" >> $GITHUB_ENV
+
+- name: Setup mise
+  uses: jdx/mise-action@v4
+  env:
+    MISE_ENV: preview
+```
+
+**After (with environment input)**:
+```yaml
+- name: Setup mise
+  uses: jdx/mise-action@v4
+  with:
+    environment: preview
+```
+
+### Environment Variable Precedence
+
+If `MISE_ENV` is already set (e.g., at the job level), it takes precedence over the `environment` input:
+
+```yaml
+jobs:
+  deploy:
+    env:
+      MISE_ENV: production  # This takes precedence
+    steps:
+      - uses: jdx/mise-action@v4
+        with:
+          environment: staging  # This will be ignored
+```
+
+### Cache Keys and Environments
+
+The cache key automatically includes the environment when using the default cache key template. You can also reference it explicitly:
+
+```yaml
+- uses: jdx/mise-action@v4
+  with:
+    environment: preview
+    cache_key: "mise-{{platform}}-{{mise_env}}-{{file_hash}}"
+```
+
+This ensures different environments maintain separate caches.
+
 ## GitHub API Rate Limits
 
 When installing tools hosted on GitHub (like `gh`, `node`, `bun`, etc.), mise needs to make API calls to GitHub's releases API. Without authentication, these calls are subject to GitHub's rate limit of 60 requests per hour, which can cause installation failures.

action.yml

@@ -85,6 +85,13 @@ inputs:
     description: "Automatically load mise env vars into GITHUB_ENV. Note that PATH modifications are not part of this."
     required: false
     default: "true"
+  environment:
+    required: false
+    description: |
+      The mise environment to use (e.g., "preview", "production"). 
+      When set, this value will be exported to GITHUB_ENV (if env input is true), 
+      making it available to all subsequent workflow steps.
+      Note: If MISE_ENV is already set in the environment, it takes precedence over this input.
 outputs:
   cache-hit:
     description: A boolean value to indicate if a cache was hit.

dist/index.js

@@ -84959,6 +84959,16 @@ async function setEnvVars() {
             exportVariable(k, v);
         }
     };
+    // Set MISE_ENV from 'environment' input if provided
+    // Note: existing MISE_ENV environment variable takes precedence
+    const environmentInput = getInput('environment');
+    if (environmentInput && !process.env.MISE_ENV) {
+        info(`Setting MISE_ENV=${environmentInput}`);
+        exportVariable('MISE_ENV', environmentInput);
+    }
+    else if (environmentInput && process.env.MISE_ENV) {
+        info(`MISE_ENV already set to '${process.env.MISE_ENV}', ignoring 'environment' input`);
+    }
     if (getBooleanInput('experimental'))
         set('MISE_EXPERIMENTAL', '1');
     const logLevel = getInput('log_level');

src/index.ts

@@ -177,6 +177,19 @@ async function setEnvVars(): Promise<void> {
       core.exportVariable(k, v)
     }
   }
+
+  // Set MISE_ENV from 'environment' input if provided
+  // Note: existing MISE_ENV environment variable takes precedence
+  const environmentInput = core.getInput('environment')
+  if (environmentInput && !process.env.MISE_ENV) {
+    core.info(`Setting MISE_ENV=${environmentInput}`)
+    core.exportVariable('MISE_ENV', environmentInput)
+  } else if (environmentInput && process.env.MISE_ENV) {
+    core.info(
+      `MISE_ENV already set to '${process.env.MISE_ENV}', ignoring 'environment' input`
+    )
+  }
+
   if (core.getBooleanInput('experimental')) set('MISE_EXPERIMENTAL', '1')
 
   const logLevel = core.getInput('log_level')