From b15f9d011ca1bf7f24ebed80fac2027042d87a81 Mon Sep 17 00:00:00 2001
From: Harmen Stoppels <me@harmenstoppels.nl>
Date: Wed, 3 Jan 2024 17:44:59 +0100
Subject: [PATCH] Spec.format: error on old style format strings (#41934)

---
 lib/spack/spack/spec.py                | 14 ++++++++++++++
 lib/spack/spack/test/spec_semantics.py |  6 ++++++
 2 files changed, 20 insertions(+)

diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 20e5c3ffa3..8c15a873af 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -213,6 +213,19 @@ def __call__(self, match):
     return clr.colorize(re.sub(_SEPARATORS, insert_color(), str(spec)) + "@.")
 
 
+OLD_STYLE_FMT_RE = re.compile(r"\${[A-Z]+}")
+
+
+def ensure_modern_format_string(fmt: str) -> None:
+    """Ensure that the format string does not contain old ${...} syntax."""
+    result = OLD_STYLE_FMT_RE.search(fmt)
+    if result:
+        raise SpecFormatStringError(
+            f"Format string `{fmt}` contains old syntax `{result.group(0)}`. "
+            "This is no longer supported."
+        )
+
+
 @lang.lazy_lexicographic_ordering
 class ArchSpec:
     """Aggregate the target platform, the operating system and the target microarchitecture."""
@@ -4360,6 +4373,7 @@ def format(self, format_string=DEFAULT_FORMAT, **kwargs):
                 that accepts a string and returns another one
 
         """
+        ensure_modern_format_string(format_string)
         color = kwargs.get("color", False)
         transform = kwargs.get("transform", {})
 
diff --git a/lib/spack/spack/test/spec_semantics.py b/lib/spack/spack/test/spec_semantics.py
index 87ed1e4b3f..08caba1518 100644
--- a/lib/spack/spack/test/spec_semantics.py
+++ b/lib/spack/spack/test/spec_semantics.py
@@ -1517,3 +1517,9 @@ def test_edge_equality_does_not_depend_on_virtual_order():
     assert edge1 == edge2
     assert tuple(sorted(edge1.virtuals)) == edge1.virtuals
     assert tuple(sorted(edge2.virtuals)) == edge1.virtuals
+
+
+def test_old_format_strings_trigger_error(default_mock_concretization):
+    s = Spec("a").concretized()
+    with pytest.raises(SpecFormatStringError):
+        s.format("${PACKAGE}-${VERSION}-${HASH}")