Prefer with_env helper over mutating ENV in specs (#16608)

The `with_env` helper still mutates `ENV` internally, but we can later fix it to mock `ENV` instead of mutating it.

Author: ysbaddaden

spec/compiler/ffi/ffi_spec.cr

@@ -5,6 +5,7 @@ require "../spec_helper"
 require "compiler/crystal/ffi"
 require "compiler/crystal/loader"
 require "../loader/spec_helper"
+require "../../support/env"
 
 # all the integral return types must be at least as large as the register size
 # to avoid integer promotion by FFI!
@@ -36,18 +37,16 @@ end
 {% end %}
 
 describe Crystal::FFI::CallInterface do
-  before_all do
+  around_all do |example|
     FileUtils.mkdir_p(SPEC_CRYSTAL_LOADER_LIB_PATH)
     build_c_dynlib(compiler_datapath("ffi", "sum.c"))
 
     {% if flag?(:win32) && flag?(:gnu) %}
-      ENV["PATH"] = "#{SPEC_CRYSTAL_LOADER_LIB_PATH}#{Process::PATH_DELIMITER}#{ENV["PATH"]}"
-    {% end %}
-  end
-
-  after_all do
-    {% if flag?(:win32) && flag?(:gnu) %}
-      ENV["PATH"] = ENV["PATH"].delete_at(0, ENV["PATH"].index!(Process::PATH_DELIMITER) + 1)
+      with_env({"PATH" => "#{SPEC_CRYSTAL_LOADER_LIB_PATH}#{Process::PATH_DELIMITER}#{ENV["PATH"]}"}) do
+        example.run
+      end
+    {% else %}
+      example.run
     {% end %}
 
     FileUtils.rm_rf(SPEC_CRYSTAL_LOADER_LIB_PATH)

spec/compiler/interpreter/lib_spec.cr

@@ -1,6 +1,7 @@
 {% skip_file if flag?(:without_interpreter) %}
 require "./spec_helper"
 require "../loader/spec_helper"
+require "../../support/env"
 
 private def ldflags
   {% if flag?(:msvc) %}
@@ -19,18 +20,16 @@ private def ldflags_with_backtick
 end
 
 describe Crystal::Repl::Interpreter do
-  before_all do
+  around_all do |example|
     FileUtils.mkdir_p(SPEC_CRYSTAL_LOADER_LIB_PATH)
     build_c_dynlib(compiler_datapath("interpreter", "sum.c"))
 
     {% if flag?(:win32) %}
-      ENV["PATH"] = "#{SPEC_CRYSTAL_LOADER_LIB_PATH}#{Process::PATH_DELIMITER}#{ENV["PATH"]}"
-    {% end %}
-  end
-
-  after_all do
-    {% if flag?(:win32) %}
-      ENV["PATH"] = ENV["PATH"].delete_at(0, ENV["PATH"].index!(Process::PATH_DELIMITER) + 1)
+      with_env({"PATH" => "#{SPEC_CRYSTAL_LOADER_LIB_PATH}#{Process::PATH_DELIMITER}#{ENV["PATH"]}"}) do
+        example.run
+      end
+    {% else %}
+      example.run
     {% end %}
 
     FileUtils.rm_rf(SPEC_CRYSTAL_LOADER_LIB_PATH)

spec/std/dir_spec.cr

@@ -1,11 +1,11 @@
 require "./spec_helper"
 require "../support/env"
 
-private def unset_tempdir(&)
+private def reset_tempdir(tmp_path = nil, &)
   {% if flag?(:windows) %}
-    with_env("TMP": nil, "TEMP": nil, "USERPROFILE": nil) { yield }
+    with_env("TMP": tmp_path, "TEMP": nil, "USERPROFILE": nil) { yield }
   {% else %}
-    with_env("TMPDIR": nil) { yield }
+    with_env("TMPDIR": tmp_path) { yield }
   {% end %}
 end
 
@@ -665,7 +665,7 @@ describe "Dir" do
 
   describe ".tempdir" do
     it "returns default directory for tempfiles" do
-      unset_tempdir do
+      reset_tempdir do
         {% if flag?(:windows) %}
           # GetTempPathW defaults to the Windows directory when %TMP%, %TEMP%
           # and %USERPROFILE% are not set.
@@ -681,9 +681,8 @@ describe "Dir" do
     end
 
     it "returns configure directory for tempfiles" do
-      unset_tempdir do
-        tmp_path = Path["my_temporary_path"].expand.to_s
-        ENV[{{ flag?(:windows) ? "TMP" : "TMPDIR" }}] = tmp_path
+      tmp_path = Path["my_temporary_path"].expand.to_s
+      reset_tempdir(tmp_path) do
         Dir.tempdir.should eq tmp_path
       end
     end