hadrian: Add test:all_deps to build just testsuite dependencies

Fixes #22534

2 files changed, 16 insertions, 0 deletions

diff --git a/hadrian/doc/testsuite.md b/hadrian/doc/testsuite.md
index 49a310d8a8..6ba289dd2b 100644
--- a/hadrian/doc/testsuite.md
+++ b/hadrian/doc/testsuite.md
@@ -22,6 +22,19 @@ tested in CI. If you use an untested flavour such as "Quick" then you run the
 risk that not all tests will pass. In particular you can rely on the `validate`
 and `perf` flavours being tested but no others.
 
+## Building just the dependencies needed for the testsuite
+
+By default the testsuite is queried to work out what specific dependencies need to
+be built for tests. For example, some linter tests don't require anything to be built.
+If you wish to build all the targets for the testsuite before running any tests there is
+a special meta-target which builds all the dependencies you might need when running the testsuite.
+
+```
+build test:all_deps
+```
+
+
+
 ## Running only a subset of the testsuite
 
 ### Specific tests
diff --git a/hadrian/src/Rules/Test.hs b/hadrian/src/Rules/Test.hs
index 0c8bd0059d..58b689bad3 100644
--- a/hadrian/src/Rules/Test.hs
+++ b/hadrian/src/Rules/Test.hs
@@ -82,6 +82,9 @@ inTreeOutTree inTree outTree = do
 testsuiteDeps :: Rules ()
 testsuiteDeps = do
   root <- buildRootRules
+  "test:all_deps" ~> do
+    need ("test:ghc" : map cp_target checkPrograms)
+
   "test:ghc" ~> inTreeOutTree
                     (\stg -> do
                       needTestsuitePackages stg