[bigdecimal] Make BigDecimal#precs deprecated

https://github.com/ruby/bigdecimal/commit/7e80e6e145
https://github.com/ruby/bigdecimal/commit/0ed7846e8c

4 files changed, 31 insertions, 10 deletions

diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index ef975a01e0..fa00395583 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -355,11 +355,12 @@ BigDecimal_double_fig(VALUE self)
 /*  call-seq:
  *     big_decimal.precs  ->  array
  *
- *  Returns an Array of two Integer values.
+ *  Returns an Array of two Integer values that represent platform-dependent
+ *  internal storage properties.
  *
- *  The first value is the current number of significant digits in the
- *  BigDecimal. The second value is the maximum number of significant digits
- *  for the BigDecimal.
+ *  This method is deprecated and will be removed in the future.
+ *  Instead, use BigDecimal#precision for obtaining the number of decimal
+ *  digits.
  *
  *     BigDecimal('5').precs #=> [9, 18]
  */
@@ -371,6 +372,10 @@ BigDecimal_prec(VALUE self)
     Real *p;
     VALUE obj;
 
+    rb_category_warn(RB_WARN_CATEGORY_DEPRECATED,
+                     "BigDecimal#precs is deprecated and will be removed in the future; "
+                     "use BigDecimal#precision instead.");
+
     GUARD_OBJ(p, GetVpValue(self, 1));
     obj = rb_assoc_new(SIZET2NUM(p->Prec*VpBaseFig()),
 		       SIZET2NUM(p->MaxPrec*VpBaseFig()));
diff --git a/ext/bigdecimal/bigdecimal.h b/ext/bigdecimal/bigdecimal.h
index e3eae06e67..28f3363b3c 100644
--- a/ext/bigdecimal/bigdecimal.h
+++ b/ext/bigdecimal/bigdecimal.h
@@ -159,6 +159,10 @@ rb_sym2str(VALUE sym)
 # define vabs llabs
 #endif
 
+#if !defined(HAVE_RB_CATEGORY_WARN) || !defined(HAVE_CONST_RB_WARN_CATEGORY_DEPRECATED)
+#   define rb_category_warn(category, ...) rb_warn(__VA_ARGS__)
+#endif
+
 extern VALUE rb_cBigDecimal;
 
 #if 0 || SIZEOF_BDIGITS >= 16
diff --git a/ext/bigdecimal/extconf.rb b/ext/bigdecimal/extconf.rb
index fc448ed380..63123e2892 100644
--- a/ext/bigdecimal/extconf.rb
+++ b/ext/bigdecimal/extconf.rb
@@ -42,6 +42,8 @@ have_func("rb_complex_imag", "ruby.h")
 have_func("rb_array_const_ptr", "ruby.h")
 have_func("rb_sym2str", "ruby.h")
 have_func("rb_opts_exception_p", "ruby.h")
+have_func("rb_category_warn", "ruby.h")
+have_const("RB_WARN_CATEGORY_DEPRECATED", "ruby.h")
 
 if File.file?(File.expand_path('../lib/bigdecimal.rb', __FILE__))
   bigdecimal_rb = "$(srcdir)/lib/bigdecimal.rb"
diff --git a/test/bigdecimal/test_bigdecimal.rb b/test/bigdecimal/test_bigdecimal.rb
index 59726adabb..3003e44a6e 100644
--- a/test/bigdecimal/test_bigdecimal.rb
+++ b/test/bigdecimal/test_bigdecimal.rb
@@ -610,12 +610,22 @@ class TestBigDecimal < Test::Unit::TestCase
     assert_operator(BigDecimal((2**100).to_s), :==, d)
   end
 
+  def test_precs_deprecated
+    assert_warn(/BigDecimal#precs is deprecated and will be removed in the future/) do
+      BigDecimal("1").precs
+    end
+  end
+
   def test_precs
-    a = BigDecimal("1").precs
-    assert_instance_of(Array, a)
-    assert_equal(2, a.size)
-    assert_kind_of(Integer, a[0])
-    assert_kind_of(Integer, a[1])
+    assert_separately(["-rbigdecimal"], "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      $VERBOSE = nil
+      a = BigDecimal("1").precs
+      assert_instance_of(Array, a)
+      assert_equal(2, a.size)
+      assert_kind_of(Integer, a[0])
+      assert_kind_of(Integer, a[1])
+    end;
   end
 
   def test_hash
@@ -764,7 +774,7 @@ class TestBigDecimal < Test::Unit::TestCase
     assert_equal(BigDecimal("0.1"), a, '[ruby-core:34318]')
 
     a, b = BigDecimal("0.11111").coerce(1.quo(3))
-    assert_equal(BigDecimal("0." + "3"*a.precs[0]), a)
+    assert_equal(BigDecimal("0." + "3"*a.precision), a)
 
     assert_nothing_raised(TypeError, '#7176') do
       BigDecimal('1') + Rational(1)