From 8e1a99026887ee836a68ae3e238fb0f2e1562447 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Wed, 10 May 2023 20:47:25 -0400
Subject: [PATCH] Expose `mkOutputString` as method of `EvalState`

---
 src/libexpr/eval.cc    | 21 +++++++++++++++++++++
 src/libexpr/eval.hh    | 33 +++++++++++++++++++++++++++++----
 src/libexpr/primops.cc | 27 +--------------------------
 3 files changed, 51 insertions(+), 30 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 0b4243670..679f46153 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1047,6 +1047,27 @@ void EvalState::mkStorePathString(const StorePath & p, Value & v)
 }
 
 
+void EvalState::mkOutputString(
+    Value & value,
+    const StorePath & drvPath,
+    const std::string outputName,
+    std::optional<StorePath> optOutputPath)
+{
+    value.mkString(
+        optOutputPath
+            ? store->printStorePath(*std::move(optOutputPath))
+            /* Downstream we would substitute this for an actual path once
+               we build the floating CA derivation */
+            : downstreamPlaceholder(*store, drvPath, outputName),
+        NixStringContext {
+            NixStringContextElem::Built {
+                .drvPath = drvPath,
+                .output = outputName,
+            }
+        });
+}
+
+
 /* Create a thunk for the delayed computation of the given expression
    in the given environment.  But if the expression is a variable,
    then look it up right away.  This significantly reduces the number
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index bb3ac2b22..3b2164a19 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -576,12 +576,37 @@ public:
     void mkThunk_(Value & v, Expr * expr);
     void mkPos(Value & v, PosIdx pos);
 
-    /* Create a string representing a store path.
-
-       The string is the printed store path with a context containing a single
-       `Opaque` element of that store path. */
+    /**
+     * Create a string representing a store path.
+     *
+     * The string is the printed store path with a context containing a single
+     * `NixStringContextElem::Opaque` element of that store path.
+     */
     void mkStorePathString(const StorePath & storePath, Value & v);
 
+    /**
+     * Create a string representing a `DerivedPath::Built`.
+     *
+     * The string is the printed store path with a context containing a single
+     * `NixStringContextElem::Built` element of the drv path and output name.
+     *
+     * @param value Value we are settings
+     *
+     * @param drvPath Path the drv whose output we are making a string for
+     *
+     * @param outputName Name of the output
+     *
+     * @param optOutputPath Optional output path for that string. Must
+     * be passed if and only if output store object is input-addressed.
+     * Will be printed to form string if passed, otherwise a placeholder
+     * will be used (see `downstreamPlaceholder()`).
+     */
+    void mkOutputString(
+        Value & value,
+        const StorePath & drvPath,
+        const std::string outputName,
+        std::optional<StorePath> optOutputPath);
+
     void concatLists(Value & v, size_t nrLists, Value * * lists, const PosIdx pos, std::string_view errorCtx);
 
     /**
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 336d756a0..6fbd66389 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -129,30 +129,6 @@ static SourcePath realisePath(EvalState & state, const PosIdx pos, Value & v, co
     }
 }
 
-/**
- * Inverse of one of the `EvalState::coerceToDerivedPath()` cases.
- */
-static void mkOutputString(
-    EvalState & state,
-    Value & value,
-    const StorePath & drvPath,
-    const std::string outputName,
-    std::optional<StorePath> optOutputPath)
-{
-    value.mkString(
-        optOutputPath
-            ? state.store->printStorePath(*std::move(optOutputPath))
-            /* Downstream we would substitute this for an actual path once
-               we build the floating CA derivation */
-            : downstreamPlaceholder(*state.store, drvPath, outputName),
-        NixStringContext {
-            NixStringContextElem::Built {
-                .drvPath = drvPath,
-                .output = outputName,
-            }
-        });
-}
-
 /**
  * Add and attribute to the given attribute map from the output name to
  * the output path, or a placeholder.
@@ -173,8 +149,7 @@ static void mkOutputString(
     const StorePath & drvPath,
     const std::pair<std::string, DerivationOutput> & o)
 {
-    mkOutputString(
-        state,
+    state.mkOutputString(
         attrs.alloc(o.first),
         drvPath,
         o.first,