String#tr: don't crash if replacement is empty (#3129)

crystal-lang · Aug 14, 2016 · 356cf4d · 356cf4d
1 parent aa7a7ea
commit 356cf4d
Showing 3 changed files with 23 additions and 14 deletions.
diff --git a/spec/std/string_spec.cr b/spec/std/string_spec.cr
@@ -1391,18 +1391,26 @@ describe "String" do
     s.bytesize.should eq(3)
   end
 
-  it "tr" do
-    "bla".tr("a", "h").should eq("blh")
-    "bla".tr("a", "⊙").should eq("bl⊙")
-    "bl⊙a".tr("⊙", "a").should eq("blaa")
-    "bl⊙a".tr("⊙", "ⓧ").should eq("blⓧa")
-    "bl⊙a⊙asdfd⊙dsfsdf⊙⊙⊙".tr("a⊙", "ⓧt").should eq("bltⓧtⓧsdfdtdsfsdfttt")
-    "hello".tr("aeiou", "*").should eq("h*ll*")
-    "hello".tr("el", "ip").should eq("hippo")
-    "Lisp".tr("Lisp", "Crys").should eq("Crys")
-    "hello".tr("helo", "1212").should eq("12112")
-    "this".tr("this", "ⓧ").should eq("ⓧⓧⓧⓧ")
-    "über".tr("ü", "u").should eq("uber")
+  describe "tr" do
+    it "translates" do
+      "bla".tr("a", "h").should eq("blh")
+      "bla".tr("a", "⊙").should eq("bl⊙")
+      "bl⊙a".tr("⊙", "a").should eq("blaa")
+      "bl⊙a".tr("⊙", "ⓧ").should eq("blⓧa")
+      "bl⊙a⊙asdfd⊙dsfsdf⊙⊙⊙".tr("a⊙", "ⓧt").should eq("bltⓧtⓧsdfdtdsfsdfttt")
+      "hello".tr("aeiou", "*").should eq("h*ll*")
+      "hello".tr("el", "ip").should eq("hippo")
+      "Lisp".tr("Lisp", "Crys").should eq("Crys")
+      "hello".tr("helo", "1212").should eq("12112")
+      "this".tr("this", "ⓧ").should eq("ⓧⓧⓧⓧ")
+      "über".tr("ü", "u").should eq("uber")
+    end
+
+    context "given no replacement characters" do
+      it "acts as #delete" do
+        "foo".tr("o", "").should eq("foo".delete("o"))
+      end
+    end
   end
 
   describe "compare" do

diff --git a/src/compiler/crystal/codegen/const.cr b/src/compiler/crystal/codegen/const.cr
@@ -30,7 +30,7 @@ require "./codegen"
 
 class Crystal::CodeGenVisitor
   # The special constants ARGC_UNSAFE and ARGV_UNSAFE need to be initialized
-  # as soon as the program starts, because we have access to argc and arv
+  # as soon as the program starts, because we have access to argc and argv
   # in the main function
   def initialize_argv_and_argc
     {"ARGC_UNSAFE", "ARGV_UNSAFE"}.each do |name|

diff --git a/src/string.cr b/src/string.cr
@@ -1179,14 +1179,15 @@ class String
 
   # Returns a new string _tr_anslating characters using *from* and *to* as a
   # map. If *to* is shorter than *from*, the last character in *to* is used for
-  # the rest.
+  # the rest. If *to* is empty, this acts like `String#delete`.
   #
   # ```
   # "aabbcc".tr("abc", "xyz") # => "xxyyzz"
   # "aabbcc".tr("abc", "x")   # => "xxxxxx"
   # "aabbcc".tr("a", "xyz")   # => "xxbbcc"
   # ```
   def tr(from : String, to : String)
+    return delete(from) if to.empty?
     multi = nil
     table = StaticArray(Int32, 256).new(-1)
     reader = Char::Reader.new(to)