♻️ Switch to object spreading rather than Object.assign (#5300)

**Description**

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As we dropped support for versions of Node not supporting object
spreading we can now use it barely everywhere needed.

Fix #5299

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**Advanced**

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- [x] Category: Refactoring
- [x] Impacts: Force users to rely on more modern versions of Node

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packages/fast-check/src/arbitrary/string.ts

@@ -35,8 +35,6 @@ export type StringConstraints = StringSharedConstraints & {
   unit?: 'grapheme' | 'grapheme-composite' | 'grapheme-ascii' | 'binary' | 'binary-ascii' | Arbitrary<string>;
 };
 
-const safeObjectAssign = Object.assign;
-
 /** @internal */
 function extractUnitArbitrary(constraints: Pick<StringConstraints, 'unit'>): Arbitrary<string> {
   if (typeof constraints.unit === 'object') {
@@ -69,9 +67,6 @@ export function string(constraints: StringConstraints = {}): Arbitrary<string> {
   const charArbitrary = extractUnitArbitrary(constraints);
   const unmapper = patternsToStringUnmapperFor(charArbitrary, constraints);
   const experimentalCustomSlices = createSlicesForString(charArbitrary, unmapper);
-  // TODO - Move back to object spreading as soon as we bump support from es2017 to es2018+
-  const enrichedConstraints: ArrayConstraintsInternal<string> = safeObjectAssign(safeObjectAssign({}, constraints), {
-    experimentalCustomSlices,
-  });
+  const enrichedConstraints: ArrayConstraintsInternal<string> = { ...constraints, experimentalCustomSlices };
   return array(charArbitrary, enrichedConstraints).map(patternsToStringMapper, unmapper);
 }

packages/fast-check/src/arbitrary/webUrl.ts

@@ -12,8 +12,6 @@ import type { SizeForArbitrary } from './_internals/helpers/MaxLengthFromMinLeng
 import { relativeSizeToSize, resolveSize } from './_internals/helpers/MaxLengthFromMinLength';
 import { webPath } from './webPath';
 
-const safeObjectAssign = Object.assign;
-
 /**
  * Constraints to be applied on {@link webUrl}
  * @remarks Since 1.14.0
@@ -69,10 +67,7 @@ export function webUrl(constraints?: WebUrlConstraints): Arbitrary<string> {
     c.authoritySettings !== undefined && c.authoritySettings.size !== undefined
       ? relativeSizeToSize(c.authoritySettings.size, resolvedSize)
       : resolvedSize;
-  // TODO - Move back to object spreading as soon as we bump support from es2017 to es2018+
-  const resolvedAuthoritySettings = safeObjectAssign(safeObjectAssign({}, c.authoritySettings), {
-    size: resolvedAuthoritySettingsSize,
-  });
+  const resolvedAuthoritySettings = { ...c.authoritySettings, size: resolvedAuthoritySettingsSize };
   const validSchemes = c.validSchemes || ['http', 'https'];
   const schemeArb = constantFrom(...validSchemes);
   const authorityArb = webAuthority(resolvedAuthoritySettings);

packages/fast-check/src/check/arbitrary/definition/Arbitrary.ts

@@ -3,8 +3,6 @@ import { Stream } from '../../../stream/Stream';
 import { cloneMethod, hasCloneMethod } from '../../symbols';
 import { Value } from './Value';
 
-const safeObjectAssign = Object.assign;
-
 /**
  * Abstract class able to generate values on type `T`
  *
@@ -201,11 +199,11 @@ class ChainArbitrary<T, U> extends Arbitrary<U> {
           : Stream.nil<Value<U>>()
       ).join(
         context.chainedArbitrary.shrink(value, context.chainedContext).map((dst) => {
-          // TODO - Move back to object spreading as soon as we bump support from es2017 to es2018+
-          const newContext: ChainArbitraryContext<T, U> = safeObjectAssign(safeObjectAssign({}, context), {
+          const newContext: ChainArbitraryContext<T, U> = {
+            ...context,
             chainedContext: dst.context,
             stoppedForOriginal: true,
-          });
+          };
           return new Value(dst.value_, newContext);
         }),
       );

packages/fast-check/src/check/runner/Runner.ts

@@ -17,8 +17,6 @@ import type { IAsyncProperty } from '../property/AsyncProperty';
 import type { IProperty } from '../property/Property';
 import type { Value } from '../arbitrary/definition/Value';
 
-const safeObjectAssign = Object.assign;
-
 /** @internal */
 function runIt<Ts>(
   property: IRawProperty<Ts>,
@@ -100,10 +98,10 @@ function check<Ts>(rawProperty: IRawProperty<Ts>, params?: Parameters<Ts>): unkn
     throw new Error('Invalid property encountered, please use a valid property');
   if (rawProperty.run == null)
     throw new Error('Invalid property encountered, please use a valid property not an arbitrary');
-  const qParams: QualifiedParameters<Ts> = QualifiedParameters.read<Ts>(
-    // TODO - Move back to object spreading as soon as we bump support from es2017 to es2018+
-    safeObjectAssign(safeObjectAssign({}, readConfigureGlobal() as Parameters<Ts>), params),
-  );
+  const qParams: QualifiedParameters<Ts> = QualifiedParameters.read<Ts>({
+    ...(readConfigureGlobal() as Parameters<Ts>),
+    ...params,
+  });
   if (qParams.reporter !== null && qParams.asyncReporter !== null)
     throw new Error('Invalid parameters encountered, reporter and asyncReporter cannot be specified together');
   if (qParams.asyncReporter !== null && !rawProperty.isAsync())