Fix josdejong#1530: apply rounding first and lowerExp and upperExp second when formatting a number

josdejong · josdejong · commit f54599a7013f · 2019-05-25T15:51:33.000+02:00
diff --git a/HISTORY.md b/HISTORY.md
@@ -121,6 +121,8 @@
   for `candela`. Thanks @mcvladthegoat.
 - Fixed `epsilon` setting being applied globally to Complex numbers.
 - Fix `math.simplify('add(2, 3)')` throwing an error.
+- Fix #1530: number formatting first applied `lowerExp` and `upperExp`
+  and after that rounded the value instead of the other way around.
 
 
 # 2019-05-18, version 5.10.3
diff --git a/src/utils/bignumber/formatter.js b/src/utils/bignumber/formatter.js
@@ -141,10 +141,11 @@ export function format (value, options) {
 
       // determine whether or not to output exponential notation
       let str
-      const exp = value.e
+      const rounded = value.toSignificantDigits(precision)
+      const exp = rounded.e
       if (exp >= lowerExp && exp < upperExp) {
         // normal number notation
-        str = value.toSignificantDigits(precision).toFixed()
+        str = rounded.toFixed()
       } else {
         // exponential notation
         str = toExponential(value, precision)
diff --git a/src/utils/number.js b/src/utils/number.js
@@ -444,11 +444,11 @@ export function toPrecision (value, precision, options) {
   const upperExp = (options && options.upperExp !== undefined) ? options.upperExp : 5
 
   const split = splitNumber(value)
-  if (split.exponent < lowerExp || split.exponent >= upperExp) {
+  const rounded = precision ? roundDigits(split, precision) : split
+  if (rounded.exponent < lowerExp || rounded.exponent >= upperExp) {
     // exponential notation
     return toExponential(value, precision)
   } else {
-    const rounded = precision ? roundDigits(split, precision) : split
     let c = rounded.coefficients
     const e = rounded.exponent
 
diff --git a/test/utils/bignumber/formatter.test.js b/test/utils/bignumber/formatter.test.js
@@ -114,6 +114,18 @@ describe('format', function () {
         assert.strictEqual(format(new B(0.999e-6), options), '9.99e-7')
         assert.strictEqual(format(new B(123456789123), options), '1.23456789123e+11')
       })
+
+      it('auto notation with custom lower and upper bound (2)', function () {
+        assert.strictEqual(format(new B(1), { lowerExp: -2 }), '1')
+        assert.strictEqual(format(new B(0.1), { lowerExp: -2 }), '0.1')
+        assert.strictEqual(format(new B(0.01), { lowerExp: -2 }), '0.01')
+        assert.strictEqual(format(new B(0.001), { lowerExp: -2 }), '1e-3')
+
+        assert.strictEqual(format(new B(0.009), { lowerExp: -2, precision: 1 }), '9e-3')
+        assert.strictEqual(format(new B(0.0096), { lowerExp: -2, precision: 1 }), '0.01')
+        assert.strictEqual(format(new B(0.01), { lowerExp: -2, precision: 1 }), '0.01')
+        assert.strictEqual(format(new B(0.001), { lowerExp: -2, precision: 1 }), '1e-3')
+      })
     })
 
     it('should format bignumbers with a custom formatting function', function () {
diff --git a/test/utils/number.test.js b/test/utils/number.test.js
@@ -288,6 +288,16 @@ describe('number', function () {
       })
 
       it('auto notation with very small custom lower bound', function () {
+        assert.strictEqual(format(1, { lowerExp: -2 }), '1')
+        assert.strictEqual(format(0.1, { lowerExp: -2 }), '0.1')
+        assert.strictEqual(format(0.01, { lowerExp: -2 }), '0.01')
+        assert.strictEqual(format(0.001, { lowerExp: -2 }), '1e-3')
+
+        assert.strictEqual(format(0.009, { lowerExp: -2, precision: 1 }), '9e-3')
+        assert.strictEqual(format(0.0096, { lowerExp: -2, precision: 1 }), '0.01')
+        assert.strictEqual(format(0.01, { lowerExp: -2, precision: 1 }), '0.01')
+        assert.strictEqual(format(0.001, { lowerExp: -2, precision: 1 }), '1e-3')
+
         assert.strictEqual(format(1e-18, { lowerExp: -30 }), '0.000000000000000001')
         assert.strictEqual(format(1e-19, { lowerExp: -30 }), '0.0000000000000000001')
         assert.strictEqual(format(1e-20, { lowerExp: -30 }), '0.00000000000000000001')
@@ -331,7 +341,7 @@ describe('number', function () {
         assert.strictEqual(format(1234567, options), '1235000')
         assert.strictEqual(format(1e+9, options), '1e+9')
         assert.strictEqual(format(1.1e+9, options), '1.1e+9')
-        assert.strictEqual(format(1e+9 - 1, options), '1000000000')
+        assert.strictEqual(format(1e+9 - 1, options), '1e+9')
         assert.strictEqual(format(1e-6, options), '0.000001')
         assert.strictEqual(format(0.999e-6, options), '9.99e-7')
         assert.strictEqual(format(123456789123, options), '1.235e+11')
@@ -451,8 +461,8 @@ describe('number', function () {
         assert.strictEqual(toPrecision(0.004, 3), '0.00400')
         assert.strictEqual(toPrecision(0.00123456, 5), '0.0012346')
         assert.strictEqual(toPrecision(999, 2), '1000')
-        assert.strictEqual(toPrecision(99900, 2), '100000')
-        assert.strictEqual(toPrecision(99999, 2), '100000')
+        assert.strictEqual(toPrecision(99900, 2), '1.0e+5')
+        assert.strictEqual(toPrecision(99999, 2), '1.0e+5')
         assert.strictEqual(toPrecision(999e7, 2), '1.0e+10')
         assert.strictEqual(toPrecision(0.00999, 2), '0.010')
         assert.strictEqual(toPrecision(-0.00999, 2), '-0.010')
