feat: Support for default values in .env.example templates using {{ VARIABLE | default_value }} syntax

Author: laysakura

.serena/.gitignore

@@ -0,0 +1 @@
+/cache

CHANGELOG.md

@@ -8,6 +8,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- Support for default values in `.env.example` templates using `{{ VARIABLE | default_value }}` syntax
+  - Works with environment variables: `{{ API_KEY | dev-key }}` - uses default when variable is not set
+  - Works with function placeholders: `{{ branch() | main }}` - uses default when branch name is not provided
+  - Supports empty string as default: `{{ VAR | }}` - uses empty string when variable is not set
+  - Whitespace around default values is automatically trimmed
+  - Environment variables always override default values when set
 
 ### Changed
 

sample/monorepo/backend/.env.example

@@ -1,4 +1,4 @@
 # Backend service
-JWT_SECRET={{ JWT_SECRET }}
+JWT_SECRET={{ JWT_SECRET | dev-secret-key-change-in-production }}
 API_PORT={{ auto_port() }}
-DOCKER_NETWORK={{ branch() }}-sprout-nw
+DOCKER_NETWORK={{ branch() | main }}-sprout-nw

sample/monorepo/frontend/.env.example

@@ -1,4 +1,4 @@
 # Frontend service
-REACT_APP_API_KEY={{ REACT_APP_API_KEY }}
+REACT_APP_API_KEY={{ REACT_APP_API_KEY | dev-api-key }}
 FRONTEND_PORT={{ auto_port() }}
-DOCKER_NETWORK={{ branch() }}-sprout-nw
+DOCKER_NETWORK={{ branch() | main }}-sprout-nw

src/sprout/utils.py

@@ -155,26 +155,56 @@ def parse_env_template(
         file_ports.update(used_ports)
 
     for line in content.splitlines():
-        # Process {{ auto_port() }} placeholders
+        # Process {{ auto_port() | default }} placeholders
         def replace_auto_port(match: re.Match[str]) -> str:
+            # Extract default value if present (group 1)
+            default_value = match.group(1)
+            if default_value is not None:
+                default_value = default_value.strip()
+
+            # Generate available port
             port = find_available_port()
             while port in file_ports:
                 port = find_available_port()
             file_ports.add(port)
             return str(port)
 
-        line = re.sub(r"{{\s*auto_port\(\)\s*}}", replace_auto_port, line)
+        line = re.sub(r"{{\s*auto_port\(\)(?:\s*\|\s*([^}]*))?\s*}}", replace_auto_port, line)
+
+        # Process {{ branch() | default }} placeholders
+        def replace_branch(match: re.Match[str]) -> str:
+            # Extract default value if present (group 1)
+            default_value = match.group(1)
+            if default_value is not None:
+                default_value = default_value.strip()
+
+            # Use branch_name if provided, otherwise use default
+            if branch_name:
+                return branch_name
+            elif default_value is not None:
+                return default_value
+            else:
+                # No branch name and no default - keep placeholder unchanged
+                return match.group(0)
 
-        # Process {{ branch() }} placeholders
-        if branch_name:
-            line = re.sub(r"{{\s*branch\(\)\s*}}", branch_name, line)
+        line = re.sub(r"{{\s*branch\(\)(?:\s*\|\s*([^}]*))?\s*}}", replace_branch, line)
 
-        # Process {{ VARIABLE }} placeholders
+        # Process {{ VARIABLE | default }} placeholders
         def replace_variable(match: re.Match[str]) -> str:
             var_name = match.group(1).strip()
+            # Extract default value if present (group 2)
+            default_value = match.group(2)
+            if default_value is not None:
+                default_value = default_value.strip()
+
             # Check environment variable first
             value = os.environ.get(var_name)
             if value is None:
+                # If default value is provided, use it
+                if default_value is not None:
+                    return default_value
+
+                # No default value - prompt user for value
                 # Create a relative path for display
                 try:
                     display_path = template_path.relative_to(Path.cwd())
@@ -196,7 +226,8 @@ def replace_variable(match: re.Match[str]) -> str:
             return value
 
         # Only match variables that don't look like function calls (no parentheses)
-        line = re.sub(r"{{\s*([^}()]+)\s*}}", replace_variable, line)
+        # Now also captures optional | default_value
+        line = re.sub(r"{{\s*([^}()]+?)(?:\s*\|\s*([^}]*))?\s*}}", replace_variable, line)
 
         lines.append(line)
 

tests/test_integration.py

@@ -239,6 +239,61 @@ def test_branch_placeholder(self, git_repo, monkeypatch):
         assert "PORT=" in env_content  # Should have a port number
         assert "COMPOSE_VAR=${BRANCH_NAME}" in env_content  # Docker syntax preserved
 
+    def test_default_values(self, git_repo, monkeypatch):
+        """Test that default values work correctly in .env.example templates."""
+        git_repo, default_branch = git_repo
+        monkeypatch.chdir(git_repo)
+
+        # Set only some environment variables
+        monkeypatch.setenv("SET_VAR", "from_environment")
+        # UNSET_VAR is not set - should use default
+
+        # Create .env.example with default values
+        env_example = git_repo / ".env.example"
+        env_example.write_text(
+            "# Test default values\n"
+            "SET_VAR={{ SET_VAR | default_value }}\n"
+            "UNSET_VAR={{ UNSET_VAR | localhost }}\n"
+            "EMPTY_VAR={{ EMPTY_VAR | }}\n"
+            "PORT={{ auto_port() | 8080 }}\n"
+            "BRANCH={{ branch() | develop }}\n"
+            "NO_DEFAULT={{ NO_DEFAULT }}\n"  # Will be prompted
+        )
+
+        # Add to git
+        subprocess.run(["git", "add", ".env.example"], cwd=git_repo, check=True)
+        subprocess.run(
+            ["git", "commit", "-m", "Add .env.example with defaults"],
+            cwd=git_repo,
+            check=True,
+        )
+
+        # Set NO_DEFAULT to avoid prompt
+        monkeypatch.setenv("NO_DEFAULT", "prompted_value")
+
+        # Create worktree
+        branch_name = "feature-test"
+        result = runner.invoke(app, ["create", branch_name])
+        assert result.exit_code == 0
+
+        # Verify .env was created with correct values
+        env_file = git_repo / ".sprout" / branch_name / ".env"
+        env_content = env_file.read_text()
+
+        # Check that environment variable overrides default
+        assert "SET_VAR=from_environment" in env_content
+        # Check that default is used when variable is not set
+        assert "UNSET_VAR=localhost" in env_content
+        # Check empty string default
+        assert "EMPTY_VAR=" in env_content or "EMPTY_VAR=\n" in env_content
+        # Check that auto_port generates a port (default not used)
+        assert "PORT=" in env_content
+        assert "PORT=8080" not in env_content  # Should be a generated port
+        # Check that branch name is used (not default)
+        assert f"BRANCH={branch_name}" in env_content
+        # Check prompted value
+        assert "NO_DEFAULT=prompted_value" in env_content
+
     def test_error_cases(self, git_repo, monkeypatch, tmp_path):
         """Test various error conditions."""
         git_repo, default_branch = git_repo

tests/test_utils.py

@@ -220,6 +220,99 @@ def test_parse_env_template_mixed_placeholders(self, tmp_path, mocker):
             "COMPOSE_VAR=${COMPOSE_VAR}"
         )
 
+    def test_parse_env_template_variable_with_default(self, tmp_path, mocker):
+        """Test parsing {{ VARIABLE | default }} when variable is not set."""
+        # Ensure the variable is not in environment
+        mocker.patch.dict(os.environ, {}, clear=False)
+        if "TEST_VAR" in os.environ:
+            del os.environ["TEST_VAR"]
+
+        template = tmp_path / ".env.example"
+        template.write_text("TEST_VAR={{ TEST_VAR | localhost }}")
+
+        result = parse_env_template(template)
+        assert result == "TEST_VAR=localhost"
+
+    def test_parse_env_template_variable_with_default_env_set(self, tmp_path, mocker):
+        """Test that environment variable overrides default value."""
+        mocker.patch.dict(os.environ, {"TEST_VAR": "custom_value"})
+
+        template = tmp_path / ".env.example"
+        template.write_text("TEST_VAR={{ TEST_VAR | localhost }}")
+
+        result = parse_env_template(template)
+        assert result == "TEST_VAR=custom_value"
+
+    def test_parse_env_template_variable_with_empty_default(self, tmp_path, mocker):
+        """Test parsing {{ VARIABLE | }} with empty string as default."""
+        mocker.patch.dict(os.environ, {}, clear=False)
+        if "EMPTY_VAR" in os.environ:
+            del os.environ["EMPTY_VAR"]
+
+        template = tmp_path / ".env.example"
+        template.write_text("EMPTY_VAR={{ EMPTY_VAR | }}")
+
+        result = parse_env_template(template)
+        assert result == "EMPTY_VAR="
+
+    def test_parse_env_template_variable_whitespace_trimming(self, tmp_path, mocker):
+        """Test that whitespace is trimmed from default values."""
+        mocker.patch.dict(os.environ, {}, clear=False)
+        if "TEST_VAR" in os.environ:
+            del os.environ["TEST_VAR"]
+
+        template = tmp_path / ".env.example"
+        template.write_text("TEST_VAR={{ TEST_VAR |   localhost   }}")
+
+        result = parse_env_template(template)
+        assert result == "TEST_VAR=localhost"
+
+    def test_parse_env_template_branch_with_default(self, tmp_path):
+        """Test parsing {{ branch() | default }} when branch_name is None."""
+        template = tmp_path / ".env.example"
+        template.write_text("BRANCH={{ branch() | main }}")
+
+        result = parse_env_template(template, branch_name=None)
+        assert result == "BRANCH=main"
+
+    def test_parse_env_template_branch_with_default_branch_set(self, tmp_path):
+        """Test that branch_name overrides default value."""
+        template = tmp_path / ".env.example"
+        template.write_text("BRANCH={{ branch() | main }}")
+
+        result = parse_env_template(template, branch_name="feature-xyz")
+        assert result == "BRANCH=feature-xyz"
+
+    def test_parse_env_template_auto_port_with_default(self, tmp_path, mocker):
+        """Test {{ auto_port() | default }} - default is captured but not used."""
+        mocker.patch("sprout.utils.find_available_port", return_value=9000)
+
+        template = tmp_path / ".env.example"
+        template.write_text("PORT={{ auto_port() | 8080 }}")
+
+        # auto_port() always generates a port, so default is not used
+        result = parse_env_template(template)
+        assert result == "PORT=9000"
+
+    def test_parse_env_template_mixed_with_defaults(self, tmp_path, mocker):
+        """Test parsing mixed placeholders with default values."""
+        mocker.patch("sprout.utils.find_available_port", return_value=8080)
+        mocker.patch.dict(os.environ, {"SET_VAR": "from_env"}, clear=False)
+        if "UNSET_VAR" in os.environ:
+            del os.environ["UNSET_VAR"]
+
+        template = tmp_path / ".env.example"
+        template.write_text(
+            "SET_VAR={{ SET_VAR | default1 }}\n"
+            "UNSET_VAR={{ UNSET_VAR | default2 }}\n"
+            "PORT={{ auto_port() | 3000 }}\n"
+            "BRANCH={{ branch() | develop }}\n"
+            "EMPTY={{ EMPTY | }}"
+        )
+
+        result = parse_env_template(template, branch_name=None)
+        assert result == ("SET_VAR=from_env\nUNSET_VAR=default2\nPORT=8080\nBRANCH=develop\nEMPTY=")
+
     def test_parse_env_template_file_not_found(self, tmp_path):
         """Test error when template file doesn't exist."""
         template = tmp_path / "nonexistent.env"