Fix formatting of large numbers

Fixes: magnusbaeck/logstash-filter-verifier#104

Author: breml

ast/ast.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"strings"
 )
 
 // A Config node represents the root node of a Logstash configuration.
@@ -407,7 +408,14 @@ func (na NumberAttribute) String() string {
 
 // ValueString returns the value of the node as a string representation.
 func (na NumberAttribute) ValueString() string {
-	return fmt.Sprintf("%v", na.Value())
+	value := fmt.Sprintf("%g", na.Value())
+	if strings.Contains(value, "e") {
+		if float64(int64(na.Value())+0) == na.Value() {
+			return fmt.Sprintf("%d", int64(na.Value()))
+		}
+		return strings.TrimRight(fmt.Sprintf("%.10f", na.Value()), "0")
+	}
+	return value
 }
 
 // CommentBlock returns the comment of the node.

logstash_config_test.go

@@ -345,6 +345,29 @@ output {}
     # Comment
   }
 }
+`,
+		},
+		// https://github.com/magnusbaeck/logstash-filter-verifier/issues/104
+		{
+			name: "large numbers with and without precission",
+			input: `filter {
+  mutate {
+    add_field => {
+      "largeint" => 2000000
+      "largeint_negative" => -2000000
+      "int32max" => 2147483647
+      "int32max_negative" => -2147483647
+      "float_with_5_precision" => 0.00001
+      "float_with_5_precision_negative" => -0.00001
+      "float_with_10_precision" => 0.0000000001
+      "float_with_10_precision_negative" => -0.0000000001
+      "largefloat_with_10_precision" => 2000000.0000000005
+      "largefloat_with_10_precision_negative" => -2000000.0000000005
+      "int32max_with_10_precision" => 2147483647.0000009537
+      "int32max_with_10_precision_negative" => -2147483647.0000009537
+    }
+  }
+}
 `,
 		},
 	}