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diff --git a/node_modules/tslib/docs/generator.md b/node_modules/tslib/docs/generator.md new file mode 100644 index 000000000..88ffb08e2 --- /dev/null +++ b/node_modules/tslib/docs/generator.md @@ -0,0 +1,486 @@ +# The `__generator` helper
+
+The `__generator` helper is a function designed to support TypeScript's down-level emit for
+async functions when targeting ES5 and earlier. But how, exactly, does it work?
+
+Here's the body of the `__generator` helper:
+
+```js
+__generator = function (thisArg, body) {
+ var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t;
+ return { next: verb(0), "throw": verb(1), "return": verb(2) };
+ function verb(n) { return function (v) { return step([n, v]); }; }
+ function step(op) {
+ if (f) throw new TypeError("Generator is already executing.");
+ while (_) try {
+ if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
+ if (y = 0, t) op = [0, t.value];
+ switch (op[0]) {
+ case 0: case 1: t = op; break;
+ case 4: _.label++; return { value: op[1], done: false };
+ case 5: _.label++; y = op[1]; op = [0]; continue;
+ case 7: op = _.ops.pop(); _.trys.pop(); continue;
+ default:
+ if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+ if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+ if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+ if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+ if (t[2]) _.ops.pop();
+ _.trys.pop(); continue;
+ }
+ op = body.call(thisArg, _);
+ } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+ if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+ }
+};
+```
+
+And here's an example of it in use:
+
+```ts
+// source
+async function func(x) {
+ try {
+ await x;
+ }
+ catch (e) {
+ console.error(e);
+ }
+ finally {
+ console.log("finally");
+ }
+}
+
+// generated
+function func(x) {
+ return __awaiter(this, void 0, void 0, function () {
+ var e_1;
+ return __generator(this, function (_a) {
+ switch (_a.label) {
+ case 0:
+ _a.trys.push([0, 1, 3, 4]);
+ return [4 /*yield*/, x];
+ case 1:
+ _a.sent();
+ return [3 /*break*/, 4];
+ case 2:
+ e_1 = _a.sent();
+ console.error(e_1);
+ return [3 /*break*/, 4];
+ case 3:
+ console.log("finally");
+ return [7 /*endfinally*/];
+ case 4: return [2 /*return*/];
+ }
+ });
+ });
+}
+```
+
+There is a lot going on in this function, so the following will break down what each part of the
+`__generator` helper does and how it works.
+
+# Opcodes
+
+The `__generator` helper uses opcodes which represent various operations that are interpreted by
+the helper to affect its internal state. The following table lists the various opcodes, their
+arguments, and their purpose:
+
+| Opcode | Arguments | Purpose |
+|----------------|-----------|--------------------------------------------------------------------------------------------------------------------------------|
+| 0 (next) | *value* | Starts the generator, or resumes the generator with *value* as the result of the `AwaitExpression` where execution was paused. |
+| 1 (throw) | *value* | Resumes the generator, throwing *value* at `AwaitExpression` where execution was paused. |
+| 2 (return) | *value* | Exits the generator, executing any `finally` blocks starting at the `AwaitExpression` where execution was paused. |
+| 3 (break) | *label* | Performs an unconditional jump to the specified label, executing any `finally` between the current instruction and the label. |
+| 4 (yield) | *value* | Suspends the generator, setting the resume point at the next label and yielding the value. |
+| 5 (yieldstar) | *value* | Suspends the generator, setting the resume point at the next label and delegating operations to the supplied value. |
+| 6 (catch) | *error* | An internal instruction used to indicate an exception that was thrown from the body of the generator. |
+| 7 (endfinally) | | Exits a finally block, resuming any previous operation (such as a break, return, throw, etc.) |
+
+# State
+The `_`, `f`, `y`, and `t` variables make up the persistent state of the `__generator` function. Each variable
+has a specific purpose, as described in the following sections:
+
+## The `_` variable
+The `__generator` helper must share state between its internal `step` orchestration function and
+the `body` function passed to the helper.
+
+```ts
+var _ = {
+ label: 0,
+ sent: function() {
+ if (t[0] & 1) // NOTE: true for `throw`, but not `next` or `catch`
+ throw t[1];
+ return sent[1];
+ },
+ trys: [],
+ ops: []
+};
+```
+
+The following table describes the members of the `_` state object and their purpose:
+
+| Name | Description |
+|---------|---------------------------------------------------------------------------------------------------------------------------|
+| `label` | Specifies the next switch case to execute in the `body` function. |
+| `sent` | Handles the completion result passed to the generator. |
+| `trys` | A stack of **Protected Regions**, which are 4-tuples that describe the labels that make up a `try..catch..finally` block. |
+| `ops` | A stack of pending operations used for `try..finally` blocks. |
+
+The `__generator` helper passes this state object to the `body` function for use with switching
+between switch cases in the body, handling completions from `AwaitExpression`, etc.
+
+## The `f` variable
+The `f` variable indicates whether the generator is currently executing, to prevent re-entry of
+the same generator during its execution.
+
+## The `y` variable
+The `y` variable stores the iterator passed to a `yieldstar` instruction to which operations should be delegated.
+
+## The `t` variable
+The `t` variable is a temporary variable that stores one of the following values:
+
+- The completion value when resuming from a `yield` or `yield*`.
+- The error value for a catch block.
+- The current **Protected Region**.
+- The verb (`next`, `throw`, or `return` method) to delegate to the expression of a `yield*`.
+- The result of evaluating the verb delegated to the expression of a `yield*`.
+
+> NOTE: None of the above cases overlap.
+
+# Protected Regions
+A **Protected Region** is a region within the `body` function that indicates a
+`try..catch..finally` statement. It consists of a 4-tuple that contains 4 labels:
+
+| Offset | Description |
+|--------|-----------------------------------------------------------------------------------------|
+| 0 | *Required* The label that indicates the beginning of a `try..catch..finally` statement. |
+| 1 | *Optional* The label that indicates the beginning of a `catch` clause. |
+| 2 | *Optional* The label that indicates the beginning of a `finally` clause. |
+| 3 | *Required* The label that indicates the end of the `try..catch..finally` statement. |
+
+# The generator object
+The final step of the `__generator` helper is the allocation of an object that implements the
+`Generator` protocol, to be used by the `__awaiter` helper:
+
+```ts
+return { next: verb(0), "throw": verb(1), "return": verb(2) };
+function verb(n) { return function (v) { return step([n, v]); }; }
+```
+
+This object translates calls to `next`, `throw`, and `return` to the appropriate Opcodes and
+invokes the `step` orchestration function to continue execution. The `throw` and `return` method
+names are quoted to better support ES3.
+
+# Orchestration
+The `step` function is the main orechestration mechanism for the `__generator` helper. It
+interprets opcodes, handles **protected regions**, and communicates results back to the caller.
+
+Here's a closer look at the `step` function:
+
+```ts
+function step(op) {
+ if (f) throw new TypeError("Generator is already executing.");
+ while (_) try {
+ if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
+ if (y = 0, t) op = [0, t.value];
+ switch (op[0]) {
+ case 0: case 1: t = op; break;
+ case 4: _.label++; return { value: op[1], done: false };
+ case 5: _.label++; y = op[1]; op = [0]; continue;
+ case 7: op = _.ops.pop(); _.trys.pop(); continue;
+ default:
+ if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+ if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+ if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+ if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+ if (t[2]) _.ops.pop();
+ _.trys.pop(); continue;
+ }
+ op = body.call(thisArg, _);
+ } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+ if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+}
+```
+
+The main body of `step` exists in a `while` loop. This allows us to continually interpret
+operations until we have reached some completion value, be it a `return`, `await`, or `throw`.
+
+## Preventing re-entry
+The first part of the `step` function is used as a check to prevent re-entry into a currently
+executing generator:
+
+```ts
+if (f) throw new TypeError("Generator is already executing.");
+```
+
+## Running the generator
+The main body of the `step` function consists of a `while` loop which continues to evaluate
+instructions until the generator exits or is suspended:
+
+```ts
+while (_) try ...
+```
+
+When the generator has run to completion, the `_` state variable will be cleared, forcing the loop
+to exit.
+
+## Evaluating the generator body.
+```ts
+try {
+ ...
+ op = body.call(thisArg, _);
+}
+catch (e) {
+ op = [6, e];
+ y = 0;
+}
+finally {
+ f = t = 0;
+}
+```
+
+Depending on the current operation, we re-enter the generator body to start or continue execution.
+Here we invoke `body` with `thisArg` as the `this` binding and the `_` state object as the only
+argument. The result is a tuple that contains the next Opcode and argument.
+
+If evaluation of the body resulted in an exception, we convert this into an Opcode 6 ("catch")
+operation to be handled in the next spin of the `while` loop. We also clear the `y` variable in
+case it is set to ensure we are no longer delegating operations as the exception occurred in
+user code *outside* of, or at the function boundary of, the delegated iterator (otherwise the
+iterator would have handled the exception itself).
+
+After executing user code, we clear the `f` flag that indicates we are executing the generator,
+as well as the `t` temporary value so that we don't hold onto values sent to the generator for
+longer than necessary.
+
+Inside of the `try..finally` statement are a series of statements that are used to evaluate the
+operations of the transformed generator body.
+
+The first thing we do is mark the generator as executing:
+
+```ts
+if (f = 1, ...)
+```
+
+Despite the fact this expression is part of the head of an `if` statement, the comma operator
+causes it to be evaluated and the result thrown out. This is a minification added purely to
+reduce the overall footprint of the helper.
+
+## Delegating `yield*`
+
+The first two statements of the `try..finally` statement handle delegation for `yield*`:
+
+```ts
+if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
+if (y = 0, t) op = [0, t.value];
+```
+
+If the `y` variable is set, and `y` has a `next`, `throw`, or `return` method (depending on the
+current operation), we invoke this method and store the return value (an IteratorResult) in `t`.
+
+If `t` indicates it is a yielded value (e.g. `t.done === false`), we return `t` to the caller.
+If `t` indicates it is a returned value (e.g. `t.done === true`), we mark the operation with the
+`next` Opcode, and the returned value.
+If `y` did not have the appropriate method, or `t` was a returned value, we reset `y` to a falsey
+value and continue processing the operation.
+
+## Handling operations
+
+The various Opcodes are handled in the following switch statement:
+
+```ts
+switch (op[0]) {
+ case 0: case 1: t = op; break;
+ case 4: _.label++; return { value: op[1], done: false };
+ case 5: _.label++; y = op[1]; op = [0]; continue;
+ case 7: op = _.ops.pop(); _.trys.pop(); continue;
+ default:
+ if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+ if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+ if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+ if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+ if (t[2]) _.ops.pop();
+ _.trys.pop(); continue;
+}
+```
+
+The following sections describe the various Opcodes:
+
+### Opcode 0 ("next") and Opcode 1 ("throw")
+```ts
+case 0: // next
+case 1: // throw
+ t = op;
+ break;
+```
+
+Both Opcode 0 ("next") and Opcode 1 ("throw") have the same behavior. The current operation is
+stored in the `t` variable and the `body` function is invoked. The `body` function should call
+`_.sent()` which will evaluate the appropriate completion result.
+
+### Opcode 4 ("yield")
+```ts
+case 4: // yield
+ _.label++;
+ return { value: op[1], done: false };
+```
+
+When we encounter Opcode 4 ("yield"), we increment the label by one to indicate the point at which
+the generator will resume execution. We then return an `IteratorResult` whose `value` is the
+yielded value, and `done` is `false`.
+
+### Opcode 5 ("yieldstar")
+```ts
+case 5: // yieldstar
+ _.label++;
+ y = op[1];
+ op = [0];
+ continue;
+```
+
+When we receive Opcode 5 ("yieldstar"), we increment the label by one to indicate the point at which
+the generator will resume execution. We then store the iterator in `op[1]` in the `y` variable, and
+set the operation to delegate to Opcode 0 ("next") with no value. Finally, we continue execution at
+the top of the loop to start delegation.
+
+### Opcode 7 ("endfinally")
+```ts
+case 7:
+ op = _.ops.pop();
+ _.trys.pop();
+ continue;
+```
+
+Opcode 7 ("endfinally") indicates that we have hit the end of a `finally` clause, and that the last
+operation recorded before entering the `finally` block should be evaluated.
+
+### Opcode 2 ("return"), Opcode 3 ("break"), and Opcode 6 ("catch")
+```ts
+default:
+ if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) {
+ _ = 0;
+ continue;
+ }
+ if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) {
+ _.label = op[1];
+ break;
+ }
+ if (op[0] === 6 && _.label < t[1]) {
+ _.label = t[1];
+ t = op;
+ break;
+ }
+ if (t && _.label < t[2]) {
+ _.label = t[2];
+ _.ops.push(op);
+ break;
+ }
+ if (t[2])
+ _.ops.pop();
+ _.trys.pop();
+ continue;
+}
+```
+
+The handling for Opcode 2 ("return"), Opcode 3 ("break") and Opcode 6 ("catch") is more
+complicated, as we must obey the specified runtime semantics of generators. The first line in this
+clause gets the current **Protected Region** if found and stores it in the `t` temp variable:
+
+```ts
+if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && ...) ...
+```
+
+The remainder of this statement, as well as the following by several `if` statements test for more
+complex conditions. The first of these is the following:
+
+```ts
+if (!(t = ...) && (op[0] === 6 || op[0] === 2)) {
+ _ = 0;
+ continue;
+}
+```
+
+If we encounter an Opcode 6 ("catch") or Opcode 2 ("return"), and we are not in a protected region,
+then this operation completes the generator by setting the `_` variable to a falsey value. The
+`continue` statement resumes execution at the top of the `while` statement, which will exit the loop
+so that we continue execution at the statement following the loop.
+
+```ts
+if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) {
+ _.label = op[1];
+ break;
+}
+```
+
+The `if` statement above handles Opcode 3 ("break") when we are either not in a **protected region**, or
+are performing an unconditional jump to a label inside of the current **protected region**. In this case
+we can unconditionally jump to the specified label.
+
+```ts
+if (op[0] === 6 && _.label < t[1]) {
+ _.label = t[1];
+ t = op;
+ break;
+}
+```
+
+The `if` statement above handles Opcode 6 ("catch") when inside the `try` block of a **protected
+region**. In this case we jump to the `catch` block, if present. We replace the value of `t` with
+the operation so that the exception can be read as the first statement of the transformed `catch`
+clause of the transformed generator body.
+
+```ts
+if (t && _.label < t[2]) {
+ _.label = t[2];
+ _.ops.push(op);
+ break;
+}
+```
+
+This `if` statement handles all Opcodes when in a **protected region** with a `finally` clause.
+As long as we are not already inside the `finally` clause, we jump to the `finally` clause and
+push the pending operation onto the `_.ops` stack. This allows us to resume execution of the
+pending operation once we have completed execution of the `finally` clause, as long as it does not
+supersede this operation with its own completion value.
+
+```ts
+if (t[2])
+ _.ops.pop();
+```
+
+Any other completion value inside of a `finally` clause will supersede the pending completion value
+from the `try` or `catch` clauses. The above `if` statement pops the pending completion from the
+stack.
+
+```ts
+_.trys.pop();
+continue;
+```
+
+The remaining statements handle the point at which we exit a **protected region**. Here we pop the
+current **protected region** from the stack and spin the `while` statement to evaluate the current
+operation again in the next **protected region** or at the function boundary.
+
+## Handling a completed generator
+Once the generator has completed, the `_` state variable will be falsey. As a result, the `while`
+loop will terminate and hand control off to the final statement of the orchestration function,
+which deals with how a completed generator is evaluated:
+
+```ts
+if (op[0] & 5)
+ throw op[1];
+return { value: op[0] ? op[1] : void 0, done: true };
+```
+
+If the caller calls `throw` on the generator it will send Opcode 1 ("throw"). If an exception
+is uncaught within the body of the generator, it will send Opcode 6 ("catch"). As the generator has
+completed, it throws the exception. Both of these cases are caught by the bitmask `5`, which does
+not collide with the only two other valid completion Opcodes.
+
+If the caller calls `next` on the generator, it will send Opcode 0 ("next"). As the generator has
+completed, it returns an `IteratorResult` where `value` is `undefined` and `done` is true.
+
+If the caller calls `return` on the generator, it will send Opcode 2 ("return"). As the generator
+has completed, it returns an `IteratorResult` where `value` is the value provided to `return`, and
+`done` is true.
\ No newline at end of file |