From ff112e924cf648f9147c674360c9993dec53136e Mon Sep 17 00:00:00 2001
From: Mark Nauwelaerts <mark.nauwelaerts@gmail.com>
Date: Thu, 26 Jan 2023 11:23:32 +0100
Subject: generator: ensure valid output double exponential notation

Fixes #67
---
 json-glib/json-generator.c  |  7 ++++++-
 json-glib/tests/generator.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/json-glib/json-generator.c b/json-glib/json-generator.c
index 40e9b02..eef41a7 100644
--- a/json-glib/json-generator.c
+++ b/json-glib/json-generator.c
@@ -360,7 +360,12 @@ dump_value (GString  *buffer,
                          g_ascii_dtostr (buf, sizeof (buf),
                                          json_value_get_double (value)));
 	/* ensure doubles don't become ints */
-	if (g_strstr_len (buf, G_ASCII_DTOSTR_BUF_SIZE, ".") == NULL)
+        /* also make sure not to append .0 that results in invalid exponential notation
+         * since the numbers should be decimal, a hex 'e' or "E" can not be mistaken
+         */
+	if (g_strstr_len (buf, G_ASCII_DTOSTR_BUF_SIZE, ".") == NULL &&
+            g_strstr_len (buf, G_ASCII_DTOSTR_BUF_SIZE, "e") == NULL &&
+            g_strstr_len (buf, G_ASCII_DTOSTR_BUF_SIZE, "E") == NULL)
 	  {
 	    g_string_append (buffer, ".0");
           }
diff --git a/json-glib/tests/generator.c b/json-glib/tests/generator.c
index 034de5a..db27b1a 100644
--- a/json-glib/tests/generator.c
+++ b/json-glib/tests/generator.c
@@ -350,6 +350,33 @@ test_double_stays_double (void)
   json_node_free (node);
 }
 
+static void
+test_double_valid (void)
+{
+  gchar *str;
+  JsonNode *node = json_node_new (JSON_NODE_VALUE);
+  JsonGenerator *generator = json_generator_new ();
+
+  json_node_set_double (node, 1e-8);
+  json_generator_set_root (generator, node);
+
+  str = json_generator_to_data (generator, NULL);
+  g_test_message ("%s: value: '%.2f' - string: '%s'",
+                G_STRFUNC,
+                json_node_get_double (node),
+                str);
+
+  /* should be valid double
+   * in particular; no trailing .0 for exponential notation */
+  gchar *end = NULL;
+  g_ascii_strtod(str, &end);
+  g_assert_cmpint (0, ==, *end);
+
+  g_free (str);
+  g_object_unref (generator);
+  json_node_free (node);
+}
+
 
 static void
 test_pretty (void)
@@ -439,6 +466,7 @@ main (int   argc,
   g_test_add_func ("/generator/nested-object", test_nested_object);
   g_test_add_func ("/generator/decimal-separator", test_decimal_separator);
   g_test_add_func ("/generator/double-stays-double", test_double_stays_double);
+  g_test_add_func ("/generator/double-valid", test_double_valid);
   g_test_add_func ("/generator/pretty", test_pretty);
 
   for (guint i = 0; i < G_N_ELEMENTS (string_fixtures); i++)
-- 
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