From 1dad4fc27ea128a11ba0077f459494c2a1ca0d5c Mon Sep 17 00:00:00 2001
From: Andrey Mokhov <andrey.mokhov@gmail.com>
Date: Thu, 14 Feb 2019 14:29:50 +0000
Subject: Hadrian: Fix untracked dependencies
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This is a preparation for #16295: https://ghc.haskell.org/trac/ghc/ticket/16295

This commit mostly focuses on getting rid of untracked dependencies,
which prevent Shake's new `--shared` feature from appropriately caching
build rules.

There are three different solutions to untracked dependencies:

* Track them! This is the obvious and the best approach, but in some
  situations we cannot use it, for example, because a build rule creates
  files whose names are not known statically and hence cannot be
  specified as the rule's outputs.

* Use Shake's `produces` to record outputs dynamically, within the rule.

* Use Shake's `historyDisable` to disable caching for a particular build
  rule. We currently use this approach only for `ghc-pkg` which mutates
  the package database and the file `package.cache`.

These two tickets are fixed as the result:

Ticket #16271: ​https://ghc.haskell.org/trac/ghc/ticket/16271

Ticket #16272: ​https://ghc.haskell.org/trac/ghc/ticket/16272 (this one
is fixed only partially: we correctly record the dependency, but we
still copy files into the RTS build tree).
---
 hadrian/src/Settings.hs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

(limited to 'hadrian/src/Settings.hs')

diff --git a/hadrian/src/Settings.hs b/hadrian/src/Settings.hs
index 519d1fc80c..fdbef1c359 100755
--- a/hadrian/src/Settings.hs
+++ b/hadrian/src/Settings.hs
@@ -1,7 +1,7 @@
 module Settings (
     getArgs, getLibraryWays, getRtsWays, flavour, knownPackages,
-    findPackageByName, isLibrary, stagePackages, programContext,
-    getIntegerPackage
+    findPackageByName, unsafeFindPackageByName, unsafeFindPackageByPath,
+    isLibrary, stagePackages, programContext, getIntegerPackage
     ) where
 
 import CommandLine
@@ -66,3 +66,13 @@ knownPackages = sort $ ghcPackages ++ userPackages
 -- Note: this is slow but we keep it simple as there are just ~50 packages
 findPackageByName :: PackageName -> Maybe Package
 findPackageByName name = find (\pkg -> pkgName pkg == name) knownPackages
+
+unsafeFindPackageByName :: PackageName -> Package
+unsafeFindPackageByName name = fromMaybe (error msg) $ findPackageByName name
+  where
+    msg = "unsafeFindPackageByName: No package with name " ++ name
+
+unsafeFindPackageByPath :: FilePath -> Package
+unsafeFindPackageByPath path = err $ find (\pkg -> pkgPath pkg == path) knownPackages
+  where
+    err = fromMaybe $ error ("findPackageByPath: No package for path " ++ path)
-- 
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