new elf fixtures, and basic tests for Pathname#rpath(=), and Pathname#interpreter(=).

Library/Homebrew/test/os/linux/pathname_spec.rb

@@ -4,19 +4,96 @@ require "extend/pathname"
 
 describe Pathname do
   let(:elf_dir) { described_class.new "#{TEST_FIXTURE_DIR}/elf" }
-  let(:sho) { elf_dir/"libhello.so.0" }
+  let(:sho) { elf_dir/"libforty.so.0" }
-  let(:exec) { elf_dir/"hello" }
+  let(:sho_without_runpath_rpath) { elf_dir/"libhello.so.0" }
+  let(:exec) { elf_dir/"hello_with_rpath" }
+
+  def patch_elfs
+    mktmpdir do |tmp_dir|
+      %w[c.elf cpp.elf go.elf rust.elf].each do |elf|
+        FileUtils.cp(elf_dir/elf, tmp_dir/elf)
+        yield tmp_dir/elf
+      end
+    end
+  end
 
   describe "#interpreter" do
     it "returns interpreter" do
       expect(exec.interpreter).to eq "/lib64/ld-linux-x86-64.so.2"
     end
+
+    it "returns nil when absent" do
+      expect(sho.interpreter).to be_nil
+    end
   end
 
   describe "#rpath" do
+    it "prefers runpath over rpath when both are present" do
+      expect(sho.rpath).to eq "runpath"
+    end
+
+    it "returns runpath or rpath" do
+      expect(exec.rpath).to eq "@@HOMEBREW_PREFIX@@/lib"
+    end
+
     it "returns nil when absent" do
-      expect(exec.rpath).to be_nil
+      expect(sho_without_runpath_rpath.rpath).to be_nil
-      expect(sho.rpath).to be_nil
+    end
+  end
+
+  describe "#patch!" do
+    # testing only patchelf.rb as HOMEBREW_PREFIX is different for tests,
+    # and DevelopmentTools.locate fails to locate patchelf
+    HOMEBREW_PATCHELF_RB_WRITE = true
+
+    let(:placeholder_prefix) { "@@HOMEBREW_PREFIX@@" }
+    let(:short_prefix) { "/home/dwarf" }
+    let(:standard_prefix) { "/home/linuxbrew/.linuxbrew" }
+    let(:long_prefix) { "/home/organized/very organized/litter/more organized than/your words can describe" }
+    let(:prefixes) { [short_prefix, standard_prefix, long_prefix] }
+
+    # file is copied as modified_elf to avoid caching issues
+    it "only interpreter" do
+      prefixes.each do |new_prefix|
+        patch_elfs do |elf|
+          interpreter = elf.interpreter.gsub(placeholder_prefix, new_prefix)
+          elf.patch!(interpreter: interpreter)
+
+          modified_elf = elf.dirname/"mod.#{elf.basename}"
+          FileUtils.cp(elf, modified_elf)
+          expect(modified_elf.interpreter).to eq interpreter
+          expect(modified_elf.rpath).to eq "@@HOMEBREW_PREFIX@@/lib"
+        end
+      end
+    end
+
+    it "only rpath" do
+      prefixes.each do |new_prefix|
+        patch_elfs do |elf|
+          rpath = elf.rpath.gsub(placeholder_prefix, new_prefix)
+          elf.patch!(rpath: rpath)
+
+          modified_elf = elf.dirname/"mod.#{elf.basename}"
+          FileUtils.cp(elf, modified_elf)
+          expect(modified_elf.interpreter).to eq "@@HOMEBREW_PREFIX@@/lib/ld.so"
+          expect(modified_elf.rpath).to eq rpath
+        end
+      end
+    end
+
+    it "both" do
+      prefixes.each do |new_prefix|
+        patch_elfs do |elf|
+          interpreter = elf.interpreter.gsub(placeholder_prefix, new_prefix)
+          rpath = elf.rpath.gsub(placeholder_prefix, new_prefix)
+          elf.patch!(interpreter: interpreter, rpath: rpath)
+
+          modified_elf = elf.dirname/"mod.#{elf.basename}"
+          FileUtils.cp(elf, modified_elf)
+          expect(modified_elf.interpreter).to eq interpreter
+          expect(modified_elf.rpath).to eq rpath
+        end
+      end
     end
   end
 end