| 1 | /// <amd-module name="@angular/compiler-cli/ngcc/src/packages/patch_ts_expando_initializer" />
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| 2 | /**
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| 3 | * Consider the following ES5 code that may have been generated for a class:
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| 4 | *
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| 5 | * ```
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| 6 | * var A = (function(){
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| 7 | * function A() {}
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| 8 | * return A;
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| 9 | * }());
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| 10 | * A.staticProp = true;
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| 11 | * ```
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| 12 | *
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| 13 | * Here, TypeScript marks the symbol for "A" as a so-called "expando symbol", which causes
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| 14 | * "staticProp" to be added as an export of the "A" symbol.
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| 15 | *
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| 16 | * In the example above, symbol "A" has been assigned some flags to indicate that it represents a
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| 17 | * class. Due to this flag, the symbol is considered an expando symbol and as such, "staticProp" is
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| 18 | * stored in `ts.Symbol.exports`.
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| 19 | *
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| 20 | * A problem arises when "A" is not at the top-level, i.e. in UMD bundles. In that case, the symbol
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| 21 | * does not have the flag that marks the symbol as a class. Therefore, TypeScript inspects "A"'s
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| 22 | * initializer expression, which is an IIFE in the above example. Unfortunately however, only IIFEs
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| 23 | * of the form `(function(){})()` qualify as initializer for an "expando symbol"; the slightly
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| 24 | * different form seen in the example above, `(function(){}())`, does not. This prevents the "A"
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| 25 | * symbol from being considered an expando symbol, in turn preventing "staticProp" from being stored
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| 26 | * in `ts.Symbol.exports`.
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| 27 | *
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| 28 | * The logic for identifying symbols as "expando symbols" can be found here:
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| 29 | * https://github.com/microsoft/TypeScript/blob/v3.4.5/src/compiler/binder.ts#L2656-L2685
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| 30 | *
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| 31 | * Notice how the `getExpandoInitializer` function is available on the "ts" namespace in the
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| 32 | * compiled bundle, so we are able to override this function to accommodate for the alternative
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| 33 | * IIFE notation. The original implementation can be found at:
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| 34 | * https://github.com/Microsoft/TypeScript/blob/v3.4.5/src/compiler/utilities.ts#L1864-L1887
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| 35 | *
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| 36 | * Issue tracked in https://github.com/microsoft/TypeScript/issues/31778
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| 37 | *
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| 38 | * @returns the function to pass to `restoreGetExpandoInitializer` to undo the patch, or null if
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| 39 | * the issue is known to have been fixed.
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| 40 | */
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| 41 | export declare function patchTsGetExpandoInitializer(): unknown;
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| 42 | export declare function restoreGetExpandoInitializer(originalGetExpandoInitializer: unknown): void;
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