> ## Documentation Index
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# Dart Pragma Annotation
A `pragma` is a built-in Dart annotation used to provide specific directives, hints, or metadata to the underlying Dart compiler, virtual machine (VM), or static analysis tools. It acts as a mechanism to pass tool-specific instructions that are outside the standard Dart language semantics, allowing developers to influence compilation, optimization, or execution behavior.
## Syntax
The `@pragma` annotation is instantiated with a required string identifier and an optional constant argument.
```text theme={"dark"}
@pragma('name', [options])
```
## Anatomy of a Pragma
* **`name` (String):** A compile-time constant string that identifies the directive. By convention, the name is namespaced using a prefix that denotes the target tool, followed by a colon and the specific instruction (e.g., `'vm:prefer-inline'`, `'dart2js:noInline'`).
* **`options` (Object?):** An optional, compile-time constant value that supplies additional parameters or configuration to the tool processing the pragma. If omitted, it defaults to `null`.
## Mechanics and Resolution
1. **Target Agnosticism:** Pragmas are designed to be safely ignored by tools that do not understand them. If the Dart VM encounters a `dart2js:` pragma, or if the analyzer encounters an unrecognized `vm:` pragma, the tool will bypass the annotation without emitting compilation errors or warnings.
2. **Compile-Time Evaluation:** Both the `name` and the `options` arguments must be strictly evaluated as compile-time constants.
3. **Application Targets:** The `@pragma` annotation can be attached to almost any Dart declaration, including libraries, classes, mixins, functions, methods, and variables.
## Syntax Visualization
```dart theme={"dark"}
// A pragma with only a name directive applied to a top-level function
@pragma('vm:prefer-inline')
int calculateOffset(int x, int y) {
return x + y;
}
// Multiple pragmas applied to a single class declaration
@pragma('dart2js:noInline')
@pragma('vm:invisible')
class ExecutionHandler {
// A pragma utilizing the optional 'options' parameter with a valid string argument
@pragma('vm:entry-point', 'call')
void invoke() {
// Method implementation
}
}
```
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