Deprecate Kernel#open and IO support for subprocess creation/forking

Deprecate Kernel#open and IO support for subprocess creation and
forking. This deprecates subprocess creation and forking in

- Kernel#open
- URI.open
- IO.binread
- IO.foreach
- IO.readlines
- IO.read
- IO.write

This behavior is slated to be removed in Ruby 4.0

[Feature #19630]

Author: flavorjones

core/io/binread_spec.rb

@@ -44,4 +44,14 @@
   it "raises an Errno::EINVAL when not passed a valid offset" do
     -> { IO.binread @fname, 0, -1  }.should raise_error(Errno::EINVAL)
   end
+
+  ruby_version_is "3.3" do
+    # https://bugs.ruby-lang.org/issues/19630
+    it "warns about deprecation given a path with a pipe" do
+      cmd = "|echo ok"
+      -> {
+        IO.binread(cmd)
+      }.should complain(/IO process creation with a leading '\|'/)
+    end
+  end
 end

core/io/foreach_spec.rb

@@ -20,15 +20,20 @@
       platform_is :windows do
         cmd = "|cmd.exe /C echo hello&echo line2"
       end
-      IO.foreach(cmd) { |l| ScratchPad << l }
+
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        IO.foreach(cmd) { |l| ScratchPad << l }
+      end
       ScratchPad.recorded.should == ["hello\n", "line2\n"]
     end
 
     platform_is_not :windows do
       it "gets data from a fork when passed -" do
         parent_pid = $$
 
-        IO.foreach("|-") { |l| ScratchPad << l }
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          IO.foreach("|-") { |l| ScratchPad << l }
+        end
 
         if $$ == parent_pid
           ScratchPad.recorded.should == ["hello\n", "from a fork\n"]
@@ -39,6 +44,16 @@
         end
       end
     end
+
+    ruby_version_is "3.3" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation given a path with a pipe" do
+        cmd = "|echo ok"
+        -> {
+          IO.foreach(cmd).to_a
+        }.should complain(/IO process creation with a leading '\|'/)
+      end
+    end
   end
 end
 

core/io/read_spec.rb

@@ -165,12 +165,19 @@
     platform_is :windows do
       cmd = "|cmd.exe /C echo hello"
     end
-    IO.read(cmd).should == "hello\n"
+
+    suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+      IO.read(cmd).should == "hello\n"
+    end
   end
 
   platform_is_not :windows do
     it "opens a pipe to a fork if the rest is -" do
-      str = IO.read("|-")
+      str = nil
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        str = IO.read("|-")
+      end
+
       if str # parent
         str.should == "hello from child\n"
       else #child
@@ -185,13 +192,18 @@
     platform_is :windows do
       cmd = "|cmd.exe /C echo hello"
     end
-    IO.read(cmd, 1).should == "h"
+
+    suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+      IO.read(cmd, 1).should == "h"
+    end
   end
 
   platform_is_not :windows do
     it "raises Errno::ESPIPE if passed an offset" do
       -> {
-        IO.read("|sh -c 'echo hello'", 1, 1)
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          IO.read("|sh -c 'echo hello'", 1, 1)
+        end
       }.should raise_error(Errno::ESPIPE)
     end
   end
@@ -202,11 +214,23 @@
     # once https://bugs.ruby-lang.org/issues/12230 is fixed.
     it "raises Errno::EINVAL if passed an offset" do
       -> {
-        IO.read("|cmd.exe /C echo hello", 1, 1)
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          IO.read("|cmd.exe /C echo hello", 1, 1)
+        end
       }.should raise_error(Errno::EINVAL)
     end
   end
 end
+
+  ruby_version_is "3.3" do
+    # https://bugs.ruby-lang.org/issues/19630
+    it "warns about deprecation given a path with a pipe" do
+      cmd = "|echo ok"
+      -> {
+        IO.read(cmd)
+      }.should complain(/IO process creation with a leading '\|'/)
+    end
+  end
 end
 
 describe "IO.read on an empty file" do

core/io/readlines_spec.rb

@@ -180,13 +180,20 @@
       platform_is :windows do
         cmd = "|cmd.exe /C echo hello&echo line2"
       end
-      lines = IO.readlines(cmd)
+
+      lines = nil
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        lines = IO.readlines(cmd)
+      end
       lines.should == ["hello\n", "line2\n"]
     end
 
     platform_is_not :windows do
       it "gets data from a fork when passed -" do
-        lines = IO.readlines("|-")
+        lines = nil
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          lines = IO.readlines("|-")
+        end
 
         if lines # parent
           lines.should == ["hello\n", "from a fork\n"]
@@ -199,6 +206,16 @@
     end
   end
 
+  ruby_version_is "3.3" do
+    # https://bugs.ruby-lang.org/issues/19630
+    it "warns about deprecation given a path with a pipe" do
+      cmd = "|echo ok"
+      -> {
+        IO.readlines(cmd)
+      }.should complain(/IO process creation with a leading '\|'/)
+    end
+  end
+
   it_behaves_like :io_readlines, :readlines
   it_behaves_like :io_readlines_options_19, :readlines
 end

core/io/write_spec.rb

@@ -215,6 +215,17 @@
         end
       end
     end
+
+    ruby_version_is "3.3" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation given a path with a pipe" do
+        -> {
+          -> {
+            IO.write("|cat", "xxx")
+          }.should output_to_fd("xxx")
+        }.should complain(/IO process creation with a leading '\|'/)
+      end
+    end
   end
 end
 

core/kernel/open_spec.rb

@@ -29,7 +29,9 @@
 
   platform_is_not :windows, :wasi do
     it "opens an io when path starts with a pipe" do
-      @io = open("|date")
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        @io = open("|date")
+      end
       begin
         @io.should be_kind_of(IO)
         @io.read
@@ -39,21 +41,27 @@
     end
 
     it "opens an io when called with a block" do
-      @output = open("|date") { |f| f.read }
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        @output = open("|date") { |f| f.read }
+      end
       @output.should_not == ''
     end
 
     it "opens an io for writing" do
-      -> do
-        bytes = open("|cat", "w") { |io| io.write(".") }
-        bytes.should == 1
-      end.should output_to_fd(".")
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        -> {
+          bytes = open("|cat", "w") { |io| io.write(".") }
+          bytes.should == 1
+        }.should output_to_fd(".")
+      end
     end
   end
 
   platform_is :windows do
     it "opens an io when path starts with a pipe" do
-      @io = open("|date /t")
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        @io = open("|date /t")
+      end
       begin
         @io.should be_kind_of(IO)
         @io.read
@@ -63,11 +71,23 @@
     end
 
     it "opens an io when called with a block" do
-      @output = open("|date /t") { |f| f.read }
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        @output = open("|date /t") { |f| f.read }
+      end
       @output.should_not == ''
     end
   end
 
+  ruby_version_is "3.3" do
+    # https://bugs.ruby-lang.org/issues/19630
+    it "warns about deprecation given a path with a pipe" do
+      cmd = "|echo ok"
+      -> {
+        open(cmd) { |f| f.read }
+      }.should complain(/Kernel#open with a leading '\|'/)
+    end
+  end
+
   it "raises an ArgumentError if not passed one argument" do
     -> { open }.should raise_error(ArgumentError)
   end