Auto merge of #80426 - jyn514:bootstrap-caching, r=Mark-Simulacrum

Don't use `self.date` unconditionally for `program_out_of_date()`

This avoids unnecessary cache invalidations for programs not affected by
the stage0 version (which is everything except the stage0 compiler
itself).

The redundant invalidations weren't noticed until now because they only
showed up on stage0 bumps, at which point people are used to rebuilding
everything anyway. I noticed it in https://github.com/rust-lang/rust/pull/79540
because I wasn't adding `self.date` to the stamp file (because I didn't realize it was necessary). Rather than
adding self.date I thought it was better to remove it from the cache key.

2 files changed, 11 insertions, 10 deletions

diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 4603e418119..f60ae02bffe 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -393,7 +393,7 @@ class RustBuild(object):
 
         if self.rustc().startswith(self.bin_root()) and \
                 (not os.path.exists(self.rustc()) or
-                 self.program_out_of_date(self.rustc_stamp())):
+                 self.program_out_of_date(self.rustc_stamp(), self.date)):
             if os.path.exists(self.bin_root()):
                 shutil.rmtree(self.bin_root())
             tarball_suffix = '.tar.xz' if support_xz() else '.tar.gz'
@@ -429,7 +429,7 @@ class RustBuild(object):
                 self.fix_bin_or_dylib("{}/bin/rustfmt".format(self.bin_root()))
                 self.fix_bin_or_dylib("{}/bin/cargo-fmt".format(self.bin_root()))
                 with output(self.rustfmt_stamp()) as rustfmt_stamp:
-                    rustfmt_stamp.write(self.date + self.rustfmt_channel)
+                    rustfmt_stamp.write(self.rustfmt_channel)
 
         if self.downloading_llvm():
             # We want the most recent LLVM submodule update to avoid downloading
@@ -456,7 +456,7 @@ class RustBuild(object):
                 for binary in ["llvm-config", "FileCheck"]:
                     self.fix_bin_or_dylib("{}/bin/{}".format(self.llvm_root(), binary))
                 with output(self.llvm_stamp()) as llvm_stamp:
-                    llvm_stamp.write(self.date + llvm_sha + str(llvm_assertions))
+                    llvm_stamp.write(llvm_sha + str(llvm_assertions))
 
     def downloading_llvm(self):
         opt = self.get_toml('download-ci-llvm', 'llvm')
@@ -623,12 +623,12 @@ class RustBuild(object):
         return os.path.join(self.llvm_root(), '.llvm-stamp')
 
 
-    def program_out_of_date(self, stamp_path, extra=""):
+    def program_out_of_date(self, stamp_path, key):
         """Check if the given program stamp is out of date"""
         if not os.path.exists(stamp_path) or self.clean:
             return True
         with open(stamp_path, 'r') as stamp:
-            return (self.date + extra) != stamp.read()
+            return key != stamp.read()
 
     def bin_root(self):
         """Return the binary root directory
diff --git a/src/bootstrap/bootstrap_test.py b/src/bootstrap/bootstrap_test.py
index 0e941e13676..61507114159 100644
--- a/src/bootstrap/bootstrap_test.py
+++ b/src/bootstrap/bootstrap_test.py
@@ -70,6 +70,7 @@ class ProgramOutOfDate(unittest.TestCase):
         self.build.build_dir = self.container
         self.rustc_stamp_path = os.path.join(self.container, "stage0",
                                              ".rustc-stamp")
+        self.key = self.build.date + str(None)
 
     def tearDown(self):
         rmtree(self.container)
@@ -78,19 +79,19 @@ class ProgramOutOfDate(unittest.TestCase):
         """Return True when the stamp file does not exists"""
         if os.path.exists(self.rustc_stamp_path):
             os.unlink(self.rustc_stamp_path)
-        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path))
+        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
     def test_dates_are_different(self):
         """Return True when the dates are different"""
         with open(self.rustc_stamp_path, "w") as rustc_stamp:
-            rustc_stamp.write("2017-06-14")
-        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path))
+            rustc_stamp.write("2017-06-14None")
+        self.assertTrue(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
     def test_same_dates(self):
         """Return False both dates match"""
         with open(self.rustc_stamp_path, "w") as rustc_stamp:
-            rustc_stamp.write("2017-06-15")
-        self.assertFalse(self.build.program_out_of_date(self.rustc_stamp_path))
+            rustc_stamp.write("2017-06-15None")
+        self.assertFalse(self.build.program_out_of_date(self.rustc_stamp_path, self.key))
 
 
 if __name__ == '__main__':