fix(number): improve float generation for precisions of form 10^-n (#2581)

Author: matthewmayer

src/modules/number/index.ts

@@ -150,7 +150,12 @@ export class NumberModule extends SimpleModuleBase {
         throw new FakerError(`Precision should be greater than 0.`);
       }
 
-      const factor = 1 / precision;
+      const logPrecision = Math.log10(precision);
+      // Workaround to get integer values for the inverse of all precisions of the form 10^-n
+      const factor =
+        precision < 1 && Number.isInteger(logPrecision)
+          ? 10 ** -logPrecision
+          : 1 / precision;
       const int = this.int({
         min: min * factor,
         max: max * factor,

test/modules/__snapshots__/finance.spec.ts.snap

@@ -24,13 +24,13 @@ exports[`finance > 42 > amount > with min and max option 1`] = `"24.98"`;
 
 exports[`finance > 42 > amount > with min option 1`] = `"380.79"`;
 
-exports[`finance > 42 > amount > with min, leagcy max, leagcy dec and leagcy symbol 1`] = `"$24.98161"`;
+exports[`finance > 42 > amount > with min, leagcy max, leagcy dec and leagcy symbol 1`] = `"$24.98160"`;
 
-exports[`finance > 42 > amount > with min, max and dec option 1`] = `"24.98161"`;
+exports[`finance > 42 > amount > with min, max and dec option 1`] = `"24.98160"`;
 
-exports[`finance > 42 > amount > with min, max, dec and symbol option 1`] = `"#24.98161"`;
+exports[`finance > 42 > amount > with min, max, dec and symbol option 1`] = `"#24.98160"`;
 
-exports[`finance > 42 > amount > with min, max, dec, symbol and autoFormat option 1`] = `"#24.98161"`;
+exports[`finance > 42 > amount > with min, max, dec, symbol and autoFormat option 1`] = `"#24.98160"`;
 
 exports[`finance > 42 > bic > noArgs 1`] = `"UYETSCLLG53"`;
 
@@ -244,13 +244,13 @@ exports[`finance > 1337 > amount > with min and max option 1`] = `"20.48"`;
 
 exports[`finance > 1337 > amount > with min option 1`] = `"269.40"`;
 
-exports[`finance > 1337 > amount > with min, leagcy max, leagcy dec and leagcy symbol 1`] = `"$20.48099"`;
+exports[`finance > 1337 > amount > with min, leagcy max, leagcy dec and leagcy symbol 1`] = `"$20.48098"`;
 
-exports[`finance > 1337 > amount > with min, max and dec option 1`] = `"20.48099"`;
+exports[`finance > 1337 > amount > with min, max and dec option 1`] = `"20.48098"`;
 
-exports[`finance > 1337 > amount > with min, max, dec and symbol option 1`] = `"#20.48099"`;
+exports[`finance > 1337 > amount > with min, max, dec and symbol option 1`] = `"#20.48098"`;
 
-exports[`finance > 1337 > amount > with min, max, dec, symbol and autoFormat option 1`] = `"#20.48099"`;
+exports[`finance > 1337 > amount > with min, max, dec, symbol and autoFormat option 1`] = `"#20.48098"`;
 
 exports[`finance > 1337 > bic > noArgs 1`] = `"OEFHLYG18IL"`;
 

test/modules/__snapshots__/location.spec.ts.snap

@@ -74,7 +74,7 @@ exports[`location > 42 > longitude > with precision option 1`] = `-45.1655588485
 
 exports[`location > 42 > nearbyGPSCoordinate > near origin 1`] = `
 [
-  0.08140632875358443,
+  0.08140632875358447,
   -0.08093642792425726,
 ]
 `;
@@ -234,7 +234,7 @@ exports[`location > 1211 > longitude > with precision option 1`] = `154.26725534
 
 exports[`location > 1211 > nearbyGPSCoordinate > near origin 1`] = `
 [
-  -0.02872111236834616,
+  -0.02872111236834621,
   0.05959024752564801,
 ]
 `;

test/modules/number.spec.ts

@@ -3,6 +3,7 @@ import { describe, expect, it } from 'vitest';
 import { faker, FakerError, SimpleFaker } from '../../src';
 import { MERSENNE_MAX_VALUE } from '../internal/mersenne-test-utils';
 import { seededTests } from '../support/seeded-runs';
+import { times } from './../support/times';
 
 describe('number', () => {
   seededTests(faker, 'number', (t) => {
@@ -259,17 +260,36 @@ describe('number', () => {
         expect(results).toEqual([0, 0.4, 0.8, 1.2, 1.6]);
       });
 
-      it('provides numbers with an exact precision', () => {
-        for (let i = 0; i < 100; i++) {
-          const actual = faker.number.float({
-            min: 0.5,
-            max: 0.99,
-            precision: 0.01,
-          });
-          expect(actual).toBe(Number(actual.toFixed(2)));
-        }
+      it('provides numbers with a given precision of 0.2', () => {
+        const results = [
+          ...new Set(
+            Array.from({ length: 50 }, () =>
+              faker.number.float({
+                min: 0,
+                max: 0.4,
+                precision: 0.2,
+              })
+            )
+          ),
+        ].sort();
+
+        expect(results).toEqual([0, 0.2, 0.4]);
       });
 
+      it.each(times(18))(
+        `provides numbers with an exact precision of 10^-%d`,
+        (exponent) => {
+          for (let i = 0; i < 100; i++) {
+            const actual = faker.number.float({
+              min: 0.5,
+              max: 0.99,
+              precision: 10 ** -exponent,
+            });
+            expect(actual).toBe(Number(actual.toFixed(exponent)));
+          }
+        }
+      );
+
       it('throws an error for precision 0', () => {
         expect(() => faker.number.float({ precision: 0 })).toThrow(
           new FakerError('Precision should be greater than 0.')