type safety
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Florian Dold
parent
690bbfcfd8
commit
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@ -14,17 +14,15 @@
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TALER; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
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*/
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/**
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* Types and helper functions for dealing with Taler amounts.
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*/
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/**
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* Imports.
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*/
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import { Checkable } from "./checkable";
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import { objectCodec, numberCodec, stringCodec, Codec } from "./codec";
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/**
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* Number of fractional units that one value unit represents.
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@ -43,38 +41,31 @@ export const fractionalLength = 8;
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*/
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export const maxAmountValue = 2 ** 52;
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/**
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* Non-negative financial amount. Fractional values are expressed as multiples
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* of 1e-8.
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*/
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@Checkable.Class()
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export class AmountJson {
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export interface AmountJson {
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/**
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* Value, must be an integer.
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*/
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@Checkable.Number()
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readonly value: number;
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/**
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* Fraction, must be an integer. Represent 1/1e8 of a unit.
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*/
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@Checkable.Number()
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readonly fraction: number;
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/**
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* Currency of the amount.
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*/
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@Checkable.String()
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readonly currency: string;
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/**
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* Verify that a value matches the schema of this class and convert it into a
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* member.
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*/
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static checked: (obj: any) => AmountJson;
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}
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const amountJsonCodec: Codec<AmountJson> = objectCodec<AmountJson>()
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.property("value", numberCodec)
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.property("currency", stringCodec)
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.build<AmountJson>("AmountJson");
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/**
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* Result of a possibly overflowing operation.
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@ -90,7 +81,6 @@ export interface Result {
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saturated: boolean;
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}
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/**
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* Get an amount that represents zero units of a currency.
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*/
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@ -102,7 +92,6 @@ export function getZero(currency: string): AmountJson {
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};
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}
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export function sum(amounts: AmountJson[]) {
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if (amounts.length <= 0) {
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throw Error("can't sum zero amounts");
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@ -110,7 +99,6 @@ export function sum(amounts: AmountJson[]) {
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return add(amounts[0], ...amounts.slice(1));
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}
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/**
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* Add two amounts. Return the result and whether
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* the addition overflowed. The overflow is always handled
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@ -124,7 +112,7 @@ export function add(first: AmountJson, ...rest: AmountJson[]): Result {
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if (value > maxAmountValue) {
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return {
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amount: { currency, value: maxAmountValue, fraction: fractionalBase - 1 },
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saturated: true
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saturated: true,
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};
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}
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let fraction = first.fraction % fractionalBase;
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@ -133,19 +121,23 @@ export function add(first: AmountJson, ...rest: AmountJson[]): Result {
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throw Error(`Mismatched currency: ${x.currency} and ${currency}`);
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}
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value = value + x.value + Math.floor((fraction + x.fraction) / fractionalBase);
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value =
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value + x.value + Math.floor((fraction + x.fraction) / fractionalBase);
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fraction = Math.floor((fraction + x.fraction) % fractionalBase);
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if (value > maxAmountValue) {
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return {
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amount: { currency, value: maxAmountValue, fraction: fractionalBase - 1 },
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saturated: true
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amount: {
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currency,
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value: maxAmountValue,
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fraction: fractionalBase - 1,
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},
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saturated: true,
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};
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}
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}
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return { amount: { currency, value, fraction }, saturated: false };
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}
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/**
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* Subtract two amounts. Return the result and whether
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* the subtraction overflowed. The overflow is always handled
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@ -180,7 +172,6 @@ export function sub(a: AmountJson, ...rest: AmountJson[]): Result {
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return { amount: { currency, value, fraction }, saturated: false };
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}
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/**
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* Compare two amounts. Returns 0 when equal, -1 when a < b
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* and +1 when a > b. Throws when currencies don't match.
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@ -209,7 +200,6 @@ export function cmp(a: AmountJson, b: AmountJson): number {
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}
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}
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/**
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* Create a copy of an amount.
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*/
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@ -221,7 +211,6 @@ export function copy(a: AmountJson): AmountJson {
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};
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}
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/**
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* Divide an amount. Throws on division by zero.
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*/
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@ -230,17 +219,16 @@ export function divide(a: AmountJson, n: number): AmountJson {
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throw Error(`Division by 0`);
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}
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if (n === 1) {
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return {value: a.value, fraction: a.fraction, currency: a.currency};
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return { value: a.value, fraction: a.fraction, currency: a.currency };
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}
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const r = a.value % n;
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return {
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currency: a.currency,
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fraction: Math.floor(((r * fractionalBase) + a.fraction) / n),
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fraction: Math.floor((r * fractionalBase + a.fraction) / n),
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value: Math.floor(a.value / n),
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};
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}
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/**
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* Check if an amount is non-zero.
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*/
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@ -248,11 +236,10 @@ export function isNonZero(a: AmountJson): boolean {
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return a.value > 0 || a.fraction > 0;
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}
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/**
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* Parse an amount like 'EUR:20.5' for 20 Euros and 50 ct.
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*/
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export function parse(s: string): AmountJson|undefined {
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export function parse(s: string): AmountJson | undefined {
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const res = s.match(/^([a-zA-Z0-9_*-]+):([0-9]+)([.][0-9]+)?$/);
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if (!res) {
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return undefined;
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@ -272,7 +259,6 @@ export function parse(s: string): AmountJson|undefined {
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};
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}
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/**
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* Parse amount in standard string form (like 'EUR:20.5'),
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* throw if the input is not a valid amount.
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@ -285,7 +271,6 @@ export function parseOrThrow(s: string): AmountJson {
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return res;
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}
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/**
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* Convert a float to a Taler amount.
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* Loss of precision possible.
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@ -298,7 +283,6 @@ export function fromFloat(floatVal: number, currency: string) {
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};
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}
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/**
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* Convert to standard human-readable string representation that's
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* also used in JSON formats.
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@ -306,7 +290,7 @@ export function fromFloat(floatVal: number, currency: string) {
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export function toString(a: AmountJson): string {
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const av = a.value + Math.floor(a.fraction / fractionalBase);
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const af = a.fraction % fractionalBase;
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let s = av.toString()
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let s = av.toString();
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if (af) {
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s = s + ".";
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@ -315,7 +299,7 @@ export function toString(a: AmountJson): string {
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if (!n) {
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break;
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}
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s = s + Math.floor(n / fractionalBase * 10).toString();
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s = s + Math.floor((n / fractionalBase) * 10).toString();
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n = (n * 10) % fractionalBase;
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}
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}
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@ -323,7 +307,6 @@ export function toString(a: AmountJson): string {
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return `${a.currency}:${s}`;
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}
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/**
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* Check if the argument is a valid amount in string form.
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*/
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@ -94,10 +94,10 @@ class ObjectCodecBuilder<T, TC> {
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* @param objectDisplayName name of the object that this codec operates on,
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* used in error messages.
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*/
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build<R extends (TC & T)>(objectDisplayName: string): Codec<R> {
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build(objectDisplayName: string): Codec<TC> {
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const propList = this.propList;
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return {
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decode(x: any, c?: Context): R {
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decode(x: any, c?: Context): TC {
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if (!c) {
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c = {
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path: [`(${objectDisplayName})`],
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@ -112,7 +112,7 @@ class ObjectCodecBuilder<T, TC> {
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);
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obj[prop.name] = propVal;
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}
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return obj as R;
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return obj as TC;
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},
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};
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}
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