Pretty-print floating point numbers in failure messages for isWithin assertions.

kluever · Google Java Core Libraries · commit de785536dd34 · 2025-01-31T11:45:54.000-08:00
RELNOTES=Pretty-print floating point numbers in failure messages for `isWithin` assertions.
PiperOrigin-RevId: 721848489
diff --git a/core/src/main/java/com/google/common/truth/BigDecimalSubject.java b/core/src/main/java/com/google/common/truth/BigDecimalSubject.java
@@ -16,7 +16,7 @@
 package com.google.common.truth;
 
 import static com.google.common.base.Preconditions.checkNotNull;
-import static com.google.common.truth.Fact.fact;
+import static com.google.common.truth.Fact.numericFact;
 import static com.google.common.truth.Fact.simpleFact;
 
 import java.math.BigDecimal;
@@ -95,7 +95,10 @@ public void isEquivalentAccordingToCompareTo(@Nullable BigDecimal expected) {
 
   private void compareValues(@Nullable BigDecimal expected) {
     if (checkNotNull(actual).compareTo(checkNotNull(expected)) != 0) {
-      failWithoutActual(fact("expected", expected), butWas(), simpleFact("(scale is ignored)"));
+      failWithoutActual(
+          numericFact("expected", expected),
+          numericFact("but was", actual),
+          simpleFact("(scale is ignored)"));
     }
   }
 }
diff --git a/core/src/main/java/com/google/common/truth/DoubleSubject.java b/core/src/main/java/com/google/common/truth/DoubleSubject.java
@@ -18,11 +18,10 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
-import static com.google.common.truth.Fact.fact;
+import static com.google.common.truth.Fact.numericFact;
 import static com.google.common.truth.Fact.simpleFact;
 import static com.google.common.truth.MathUtil.equalWithinTolerance;
 import static com.google.common.truth.MathUtil.notEqualWithinTolerance;
-import static com.google.common.truth.Platform.doubleToString;
 import static java.lang.Double.NaN;
 import static java.lang.Double.doubleToLongBits;
 
@@ -115,9 +114,9 @@ public void of(double expected) {
 
         if (!equalWithinTolerance(actual, expected, tolerance)) {
           failWithoutActual(
-              fact("expected", doubleToString(expected)),
-              butWas(),
-              fact("outside tolerance", doubleToString(tolerance)));
+              numericFact("expected", expected),
+              numericFact("but was", actual),
+              numericFact("outside tolerance", tolerance));
         }
       }
     };
@@ -154,9 +153,9 @@ public void of(double expected) {
 
         if (!notEqualWithinTolerance(actual, expected, tolerance)) {
           failWithoutActual(
-              fact("expected not to be", doubleToString(expected)),
-              butWas(),
-              fact("within tolerance", doubleToString(tolerance)));
+              numericFact("expected not to be", expected),
+              numericFact("but was", actual),
+              numericFact("within tolerance", tolerance));
         }
       }
     };
diff --git a/core/src/main/java/com/google/common/truth/Fact.java b/core/src/main/java/com/google/common/truth/Fact.java
@@ -20,10 +20,13 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Strings.padEnd;
 import static com.google.common.base.Strings.padStart;
+import static com.google.common.truth.Platform.doubleToString;
+import static com.google.common.truth.Platform.floatToString;
 import static java.lang.Math.max;
 
 import com.google.common.collect.ImmutableList;
 import java.io.Serializable;
+import java.math.BigDecimal;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -68,29 +71,58 @@ public static Fact simpleFact(String key) {
    * Creates a fact with the given key and value, which will be printed in a format like "key:
    * value." The numeric value is converted to a string with delimiting commas.
    */
-  static Fact numericFact(String key, @Nullable Long value) {
+  static Fact numericFact(String key, @Nullable Number value) {
     return new Fact(key, formatNumericValue(value), true);
   }
 
   /**
-   * Creates a fact with the given key and value, which will be printed in a format like "key:
-   * value." The numeric value is converted to a string with delimiting commas.
+   * Formats the given numeric value as a string with delimiting commas.
+   *
+   * <p><b>Note:</b> only {@code Long}, {@code Integer}, {@code Float}, {@code Double} and {@link
+   * BigDecimal} are supported.
    */
-  static Fact numericFact(String key, @Nullable Integer value) {
-    return new Fact(key, formatNumericValue(value), true);
-  }
-
-  static String formatNumericValue(@Nullable Object value) {
+  static String formatNumericValue(@Nullable Number value) {
     if (value == null) {
       return "null";
     }
+    // the value must be a numeric type
+    checkArgument(
+        value instanceof Long
+            || value instanceof Integer
+            || value instanceof Float
+            || value instanceof Double
+            || value instanceof BigDecimal,
+        "Value (%s) must be either a Long, Integer, Float, Double, or BigDecimal.",
+        value);
+
+    // DecimalFormat is not available on all platforms, so we do the formatting manually.
+
+    if (!(value instanceof BigDecimal) && isInfiniteOrNaN(value.doubleValue())) {
+      return value.toString();
+    }
+    String stringValue =
+        value instanceof Double
+            ? doubleToString((double) value)
+            : value instanceof Float //
+                ? floatToString((float) value)
+                : value.toString();
+    if (stringValue.contains("E")) {
+      return stringValue;
+    }
+    int decimalIndex = stringValue.indexOf('.');
+    if (decimalIndex == -1) {
+      return formatWholeNumericValue(stringValue);
+    }
+    String wholeNumbers = stringValue.substring(0, decimalIndex);
+    String decimal = stringValue.substring(decimalIndex);
+    return formatWholeNumericValue(wholeNumbers) + decimal;
+  }
 
-    // We only support Long and Integer for now; maybe FP numbers in the future?
-    checkArgument(value instanceof Long || value instanceof Integer);
-
-    // DecimalFormat is not available on all platforms
-    String stringValue = String.valueOf(value);
+  private static boolean isInfiniteOrNaN(double d) {
+    return Double.isInfinite(d) || Double.isNaN(d);
+  }
 
+  private static String formatWholeNumericValue(String stringValue) {
     boolean isNegative = stringValue.startsWith("-");
     if (isNegative) {
       stringValue = stringValue.substring(1);
@@ -132,13 +164,18 @@ public String toString() {
    */
   static String makeMessage(ImmutableList<String> messages, ImmutableList<Fact> facts) {
     int longestKeyLength = 0;
-    int longestValueLength = 0;
+    int longestIntPartValueLength = 0;
     boolean seenNewlineInValue = false;
     for (Fact fact : facts) {
       if (fact.value != null) {
         longestKeyLength = max(longestKeyLength, fact.key.length());
         if (fact.padStart) {
-          longestValueLength = max(longestValueLength, fact.value.length());
+          int decimalIndex = fact.value.indexOf('.');
+          if (decimalIndex != -1) {
+            longestIntPartValueLength = max(longestIntPartValueLength, decimalIndex);
+          } else {
+            longestIntPartValueLength = max(longestIntPartValueLength, fact.value.length());
+          }
         }
         // TODO(cpovirk): Look for other kinds of newlines.
         seenNewlineInValue |= fact.value.contains("\n");
@@ -172,7 +209,14 @@ static String makeMessage(ImmutableList<String> messages, ImmutableList<Fact> fa
         builder.append(padEnd(fact.key, longestKeyLength, ' '));
         builder.append(": ");
         if (fact.padStart) {
-          builder.append(padStart(fact.value, longestValueLength, ' '));
+          int decimalIndex = fact.value.indexOf('.');
+          if (decimalIndex != -1) {
+            builder.append(
+                padStart(fact.value.substring(0, decimalIndex), longestIntPartValueLength, ' '));
+            builder.append(fact.value.substring(decimalIndex));
+          } else {
+            builder.append(padStart(fact.value, longestIntPartValueLength, ' '));
+          }
         } else {
           builder.append(fact.value);
         }
diff --git a/core/src/main/java/com/google/common/truth/FloatSubject.java b/core/src/main/java/com/google/common/truth/FloatSubject.java
@@ -18,11 +18,10 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
-import static com.google.common.truth.Fact.fact;
+import static com.google.common.truth.Fact.numericFact;
 import static com.google.common.truth.Fact.simpleFact;
 import static com.google.common.truth.MathUtil.equalWithinTolerance;
 import static com.google.common.truth.MathUtil.notEqualWithinTolerance;
-import static com.google.common.truth.Platform.floatToString;
 import static java.lang.Float.NaN;
 import static java.lang.Float.floatToIntBits;
 
@@ -123,9 +122,9 @@ public void of(float expected) {
 
         if (!equalWithinTolerance(actual, expected, tolerance)) {
           failWithoutActual(
-              fact("expected", floatToString(expected)),
-              butWas(),
-              fact("outside tolerance", floatToString(tolerance)));
+              numericFact("expected", expected),
+              numericFact("but was", actual),
+              numericFact("outside tolerance", tolerance));
         }
       }
     };
@@ -162,9 +161,9 @@ public void of(float expected) {
 
         if (!notEqualWithinTolerance(actual, expected, tolerance)) {
           failWithoutActual(
-              fact("expected not to be", floatToString(expected)),
-              butWas(),
-              fact("within tolerance", floatToString(tolerance)));
+              numericFact("expected not to be", expected),
+              numericFact("but was", actual),
+              numericFact("within tolerance", tolerance));
         }
       }
     };
diff --git a/core/src/test/java/com/google/common/truth/BigDecimalSubjectTest.java b/core/src/test/java/com/google/common/truth/BigDecimalSubjectTest.java
@@ -83,6 +83,19 @@ public void isEqualToIgnoringScale_string() {
     assertFailureValue("but was", "10");
   }
 
+  @Test
+  public void isEqualToIgnoringScale_stringWithDecimals() {
+    BigDecimal tenFour = new BigDecimal("10.4");
+    assertThat(tenFour).isEqualToIgnoringScale("10.4");
+    assertThat(tenFour).isEqualToIgnoringScale("10.4");
+    assertThat(tenFour).isEqualToIgnoringScale("10.40");
+    assertThat(tenFour).isEqualToIgnoringScale("10.400");
+    expectFailureWhenTestingThat(tenFour).isEqualToIgnoringScale("3.4");
+    assertFailureKeys("expected", "but was", "(scale is ignored)");
+    assertFailureValue("expected", "3.4");
+    assertFailureValue("but was", "10.4");
+  }
+
   private BigDecimalSubject expectFailureWhenTestingThat(BigDecimal actual) {
     return expectFailure.whenTesting().that(actual);
   }
diff --git a/core/src/test/java/com/google/common/truth/DoubleSubjectTest.java b/core/src/test/java/com/google/common/truth/DoubleSubjectTest.java
@@ -16,7 +16,7 @@
 package com.google.common.truth;
 
 import static com.google.common.truth.ExpectFailure.assertThat;
-import static com.google.common.truth.Platform.doubleToString;
+import static com.google.common.truth.Fact.formatNumericValue;
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.fail;
 
@@ -109,9 +109,9 @@ public void invokeAssertion(SimpleSubjectBuilder<DoubleSubject, Double> expect)
         .factKeys()
         .containsExactly("expected", "but was", "outside tolerance")
         .inOrder();
-    assertThat(failure).factValue("expected").isEqualTo(doubleToString(expected));
-    assertThat(failure).factValue("but was").isEqualTo(doubleToString(actual));
-    assertThat(failure).factValue("outside tolerance").isEqualTo(doubleToString(tolerance));
+    assertThat(failure).factValue("expected").isEqualTo(formatNumericValue(expected));
+    assertThat(failure).factValue("but was").isEqualTo(formatNumericValue(actual));
+    assertThat(failure).factValue("outside tolerance").isEqualTo(formatNumericValue(tolerance));
   }
 
   @Test
@@ -137,8 +137,8 @@ public void invokeAssertion(SimpleSubjectBuilder<DoubleSubject, Double> expect)
           }
         };
     AssertionError failure = expectFailure(callback);
-    assertThat(failure).factValue("expected not to be").isEqualTo(doubleToString(expected));
-    assertThat(failure).factValue("within tolerance").isEqualTo(doubleToString(tolerance));
+    assertThat(failure).factValue("expected not to be").isEqualTo(formatNumericValue(expected));
+    assertThat(failure).factValue("within tolerance").isEqualTo(formatNumericValue(tolerance));
   }
 
   @Test
diff --git a/core/src/test/java/com/google/common/truth/FactTest.java b/core/src/test/java/com/google/common/truth/FactTest.java
diff --git a/core/src/test/java/com/google/common/truth/FloatSubjectTest.java b/core/src/test/java/com/google/common/truth/FloatSubjectTest.java

Original file line number	Diff line number	Diff line change
`@@ -16,7 +16,7 @@`
`16`	`16`	`package com.google.common.truth;`
`17`	`17`
`18`	`18`	`import static com.google.common.base.Preconditions.checkNotNull;`
`19`		`-import static com.google.common.truth.Fact.fact;`
	`19`	`+import static com.google.common.truth.Fact.numericFact;`
`20`	`20`	`import static com.google.common.truth.Fact.simpleFact;`
`21`	`21`
`22`	`22`	`import java.math.BigDecimal;`
`@@ -95,7 +95,10 @@ public void isEquivalentAccordingToCompareTo(@Nullable BigDecimal expected) {`
`95`	`95`
`96`	`96`	`private void compareValues(@Nullable BigDecimal expected) {`
`97`	`97`	`if (checkNotNull(actual).compareTo(checkNotNull(expected)) != 0) {`
`98`		`- failWithoutActual(fact("expected", expected), butWas(), simpleFact("(scale is ignored)"));`
	`98`	`+ failWithoutActual(`
	`99`	`+ numericFact("expected", expected),`
	`100`	`+ numericFact("but was", actual),`
	`101`	`+ simpleFact("(scale is ignored)"));`
`99`	`102`	`}`
`100`	`103`	`}`
`101`	`104`	`}`