From d564ac1c5086bda75388d21a25583b2c9809f086 Mon Sep 17 00:00:00 2001
From: Carlo Nucera <carlo.nucera@protonmail.com>
Date: Mon, 27 Jul 2020 16:42:02 -0400
Subject: [PATCH] Offer a safer interface for pathOpt

The new interface we offer provides a way of getting all the
DerivationOutputs with the storePaths directly, based on the observation
that it's the most common usecase.
---
 src/libstore/derivations.cc | 21 +++++++++++++++++++++
 src/libstore/derivations.hh | 19 +++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index c88bb3c6d..944d89fe5 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -581,6 +581,27 @@ StringSet BasicDerivation::outputNames() const
     return names;
 }
 
+DerivationOutputsAndPaths BasicDerivation::outputsAndPaths(const Store & store) const {
+    DerivationOutputsAndPaths outsAndPaths;
+    for (auto output : outputs)
+        outsAndPaths.insert(std::make_pair(
+            output.first,
+            std::make_pair(output.second, output.second.path(store, name))
+            )
+        );
+    return outsAndPaths;
+}
+
+DerivationOutputsAndOptPaths BasicDerivation::outputsAndOptPaths(const Store & store) const {
+    DerivationOutputsAndOptPaths outsAndOptPaths;
+    for (auto output : outputs)
+        outsAndOptPaths.insert(std::make_pair(
+            output.first,
+            std::make_pair(output.second, output.second.pathOpt(store, output.first))
+            )
+        );
+    return outsAndOptPaths;
+}
 
 std::string_view BasicDerivation::nameFromPath(const StorePath & drvPath) {
     auto nameWithSuffix = drvPath.name();
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index b1cda85cb..b0cb870a2 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -41,6 +41,9 @@ struct DerivationOutput
         DerivationOutputFloating
     > output;
     std::optional<HashType> hashAlgoOpt(const Store & store) const;
+    /* Note, when you use this function you should make sure that you're passing
+       the right derivation name. When in doubt, you should use the safer
+       interface provided by BasicDerivation::outputsAndPaths */
     std::optional<StorePath> pathOpt(const Store & store, std::string_view drvName) const;
     /* DEPRECATED: Remove after CA drvs are fully implemented */
     StorePath path(const Store & store, std::string_view drvName) const {
@@ -52,6 +55,15 @@ struct DerivationOutput
 
 typedef std::map<string, DerivationOutput> DerivationOutputs;
 
+/* These are analogues to the previous DerivationOutputs data type, but they
+   also contains, for each output, the (optional) store path in which it would
+   be written. To calculate values of these types, see the corresponding
+   functions in BasicDerivation */
+typedef std::map<string, std::pair<DerivationOutput, StorePath>>
+  DerivationOutputsAndPaths;
+typedef std::map<string, std::pair<DerivationOutput, std::optional<StorePath>>>
+  DerivationOutputsAndOptPaths;
+
 /* For inputs that are sub-derivations, we specify exactly which
    output IDs we are interested in. */
 typedef std::map<StorePath, StringSet> DerivationInputs;
@@ -101,6 +113,13 @@ struct BasicDerivation
     /* Return the output names of a derivation. */
     StringSet outputNames() const;
 
+    /* Calculates the maps that contains all the DerivationOutputs, but
+       augmented with knowledge of the Store paths they would be written into.
+       The first one of these functions will be removed when the CA work is
+       completed */
+    DerivationOutputsAndPaths outputsAndPaths(const Store & store) const;
+    DerivationOutputsAndOptPaths outputsAndOptPaths(const Store & store) const;
+
     static std::string_view nameFromPath(const StorePath & storePath);
 };