testsuite: Run testsuite dependency calculation before GHC is builtwip/lint-testsuite

The main motivation for this patch is to allow tests to be added to the
testsuite which test things about the source tree without needing to
build GHC. In particular the notes linter can easily start failing and
by integrating it into the testsuite the  process of observing these
changes is caught by normal validation procedures rather than having to
run the linter specially.

With this patch I can run

```
./hadrian/build test --flavour=devel2  --only="uniques"
```

In a clean tree to run the checkUniques linter without having to build
GHC.

Fixes #21029

3 files changed, 54 insertions, 0 deletions

diff --git a/testsuite/tests/linters/Makefile b/testsuite/tests/linters/Makefile
new file mode 100644
index 0000000000..aeaef050e1
--- /dev/null
+++ b/testsuite/tests/linters/Makefile
@@ -0,0 +1,4 @@
+TOP=../..
+
+uniques:
+	python3 checkUniques/check-uniques.py $(TOP)/..
diff --git a/testsuite/tests/linters/all.T b/testsuite/tests/linters/all.T
new file mode 100644
index 0000000000..b4cc4bb8b3
--- /dev/null
+++ b/testsuite/tests/linters/all.T
@@ -0,0 +1 @@
+test('uniques', [no_deps, extra_files(["checkUniques"])], makefile_test, ['uniques'])
diff --git a/testsuite/tests/linters/checkUniques/check-uniques.py b/testsuite/tests/linters/checkUniques/check-uniques.py
new file mode 100755
index 0000000000..dd5891b0d8
--- /dev/null
+++ b/testsuite/tests/linters/checkUniques/check-uniques.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+
+import os.path
+import sys
+import re
+import glob
+import io
+from collections import defaultdict
+
+# keyed on unique type, values are lists of (unique, name) pairs
+def find_uniques(source_files):
+    uniques = defaultdict(lambda: defaultdict(lambda: set()))
+    unique_re = re.compile(r"([\w\d]+)\s*=\s*mk([\w\d']+)Unique\s+(\d+)")
+    for f in source_files:
+        ms = unique_re.findall(io.open(f, encoding='utf8').read())
+        for name, _type, n in ms:
+            uniques[_type][int(n)].add(name)
+
+    return uniques
+
+def print_all(uniques):
+    for _type, uniqs in uniques.items():
+        print('{_type} uniques'.format(**locals()))
+        for n,names in uniqs.items():
+            all_names = ', '.join(names)
+            print('  {n} = {all_names}'.format(**locals()))
+
+def find_conflicts(uniques):
+    return [ (uniqueType, number, names)
+             for uniqueType, uniqs in uniques.items()
+             for number, names in uniqs.items()
+             if len(names) > 1
+           ]
+
+top_dir = sys.argv[1]
+uniques = find_uniques(glob.glob(os.path.join(top_dir, 'compiler', 'GHC', '**', '*.hs'), recursive=True))
+#print_all(uniques)
+conflicts = find_conflicts(uniques)
+if len(uniques) < 5:
+    print("Error: check-uniques: run from wrong directory?")
+    sys.exit(1)
+
+if len(conflicts) > 0:
+    print("Error: check-uniques: Found Unique conflict")
+    print()
+    for (ty, n, names) in conflicts:
+        print('    %s unique %d conflict: %s' % (ty, n, ', '.join(names)))
+    print()
+    sys.exit(1)