1 files changed, 199 insertions, 0 deletions
diff --git a/third_party/nix/src/libexpr/primops/context.cc b/third_party/nix/src/libexpr/primops/context.cc
new file mode 100644
index 000000000000..481a2910bf84
--- /dev/null
+++ b/third_party/nix/src/libexpr/primops/context.cc
@@ -0,0 +1,199 @@
+#include "derivations.hh"
+#include "eval-inline.hh"
+#include "primops.hh"
+
+namespace nix {
+
+static void prim_unsafeDiscardStringContext(EvalState& state, const Pos& pos,
+                                            Value** args, Value& v) {
+  PathSet context;
+  std::string s = state.coerceToString(pos, *args[0], context);
+  mkString(v, s, PathSet());
+}
+
+static RegisterPrimOp r1("__unsafeDiscardStringContext", 1,
+                         prim_unsafeDiscardStringContext);
+
+static void prim_hasContext(EvalState& state, const Pos& pos, Value** args,
+                            Value& v) {
+  PathSet context;
+  state.forceString(*args[0], context, pos);
+  mkBool(v, !context.empty());
+}
+
+static RegisterPrimOp r2("__hasContext", 1, prim_hasContext);
+
+/* Sometimes we want to pass a derivation path (i.e. pkg.drvPath) to a
+   builder without causing the derivation to be built (for instance,
+   in the derivation that builds NARs in nix-push, when doing
+   source-only deployment).  This primop marks the string context so
+   that builtins.derivation adds the path to drv.inputSrcs rather than
+   drv.inputDrvs. */
+static void prim_unsafeDiscardOutputDependency(EvalState& state, const Pos& pos,
+                                               Value** args, Value& v) {
+  PathSet context;
+  std::string s = state.coerceToString(pos, *args[0], context);
+
+  PathSet context2;
+  for (auto& p : context) {
+    context2.insert(p.at(0) == '=' ? std::string(p, 1) : p);
+  }
+
+  mkString(v, s, context2);
+}
+
+static RegisterPrimOp r3("__unsafeDiscardOutputDependency", 1,
+                         prim_unsafeDiscardOutputDependency);
+
+/* Extract the context of a string as a structured Nix value.
+
+   The context is represented as an attribute set whose keys are the
+   paths in the context set and whose values are attribute sets with
+   the following keys:
+     path: True if the relevant path is in the context as a plain store
+           path (i.e. the kind of context you get when interpolating
+           a Nix path (e.g. ./.) into a string). False if missing.
+     allOutputs: True if the relevant path is a derivation and it is
+                  in the context as a drv file with all of its outputs
+                  (i.e. the kind of context you get when referencing
+                  .drvPath of some derivation). False if missing.
+     outputs: If a non-empty list, the relevant path is a derivation
+              and the provided outputs are referenced in the context
+              (i.e. the kind of context you get when referencing
+              .outPath of some derivation). Empty list if missing.
+   Note that for a given path any combination of the above attributes
+   may be present.
+*/
+static void prim_getContext(EvalState& state, const Pos& pos, Value** args,
+                            Value& v) {
+  struct ContextInfo {
+    bool path = false;
+    bool allOutputs = false;
+    Strings outputs;
+  };
+  PathSet context;
+  state.forceString(*args[0], context, pos);
+  auto contextInfos = std::map<Path, ContextInfo>();
+  for (const auto& p : context) {
+    Path drv;
+    std::string output;
+    const Path* path = &p;
+    if (p.at(0) == '=') {
+      drv = std::string(p, 1);
+      path = &drv;
+    } else if (p.at(0) == '!') {
+      std::pair<std::string, std::string> ctx = decodeContext(p);
+      drv = ctx.first;
+      output = ctx.second;
+      path = &drv;
+    }
+    auto isPath = drv.empty();
+    auto isAllOutputs = (!drv.empty()) && output.empty();
+
+    auto iter = contextInfos.find(*path);
+    if (iter == contextInfos.end()) {
+      contextInfos.emplace(
+          *path,
+          ContextInfo{isPath, isAllOutputs,
+                      output.empty() ? Strings{} : Strings{std::move(output)}});
+    } else {
+      if (isPath)
+        iter->second.path = true;
+      else if (isAllOutputs)
+        iter->second.allOutputs = true;
+      else
+        iter->second.outputs.emplace_back(std::move(output));
+    }
+  }
+
+  state.mkAttrs(v, contextInfos.size());
+
+  auto sPath = state.symbols.Create("path");
+  auto sAllOutputs = state.symbols.Create("allOutputs");
+  for (const auto& info : contextInfos) {
+    auto& infoVal = *state.allocAttr(v, state.symbols.Create(info.first));
+    state.mkAttrs(infoVal, 3);
+    if (info.second.path) {
+      mkBool(*state.allocAttr(infoVal, sPath), true);
+    }
+    if (info.second.allOutputs)
+      mkBool(*state.allocAttr(infoVal, sAllOutputs), true);
+    if (!info.second.outputs.empty()) {
+      auto& outputsVal = *state.allocAttr(infoVal, state.sOutputs);
+      state.mkList(outputsVal, info.second.outputs.size());
+      size_t i = 0;
+      for (const auto& output : info.second.outputs) {
+        mkString(*(outputsVal.listElems()[i++] = state.allocValue()), output);
+      }
+    }
+  }
+}
+
+static RegisterPrimOp r4("__getContext", 1, prim_getContext);
+
+/* Append the given context to a given string.
+
+   See the commentary above unsafeGetContext for details of the
+   context representation.
+*/
+static void prim_appendContext(EvalState& state, const Pos& pos, Value** args,
+                               Value& v) {
+  PathSet context;
+  auto orig = state.forceString(*args[0], context, pos);
+
+  state.forceAttrs(*args[1], pos);
+
+  auto sPath = state.symbols.Create("path");
+  auto sAllOutputs = state.symbols.Create("allOutputs");
+  for (const auto& attr_iter : *args[1]->attrs) {
+    const Attr* i = &attr_iter.second;  // TODO(tazjin): get rid of this
+    if (!state.store->isStorePath(i->name))
+      throw EvalError("Context key '%s' is not a store path, at %s", i->name,
+                      i->pos);
+    if (!settings.readOnlyMode) {
+      state.store->ensurePath(i->name);
+    }
+    state.forceAttrs(*i->value, *i->pos);
+    auto iter = i->value->attrs->find(sPath);
+    if (iter != i->value->attrs->end()) {
+      if (state.forceBool(*iter->second.value, *iter->second.pos)) {
+        context.insert(i->name);
+      }
+    }
+
+    iter = i->value->attrs->find(sAllOutputs);
+    if (iter != i->value->attrs->end()) {
+      if (state.forceBool(*iter->second.value, *iter->second.pos)) {
+        if (!isDerivation(i->name)) {
+          throw EvalError(
+              "Tried to add all-outputs context of %s, which is not a "
+              "derivation, to a string, at %s",
+              i->name, i->pos);
+        }
+        context.insert("=" + std::string(i->name));
+      }
+    }
+
+    iter = i->value->attrs->find(state.sOutputs);
+    if (iter != i->value->attrs->end()) {
+      state.forceList(*iter->second.value, *iter->second.pos);
+      if (iter->second.value->listSize() && !isDerivation(i->name)) {
+        throw EvalError(
+            "Tried to add derivation output context of %s, which is not a "
+            "derivation, to a string, at %s",
+            i->name, i->pos);
+      }
+      for (unsigned int n = 0; n < iter->second.value->listSize(); ++n) {
+        auto name = state.forceStringNoCtx(*iter->second.value->listElems()[n],
+                                           *iter->second.pos);
+        context.insert("!" + name + "!" + std::string(i->name));
+      }
+    }
+  }
+
+  mkString(v, orig, context);
+}
+
+static RegisterPrimOp r5("__appendContext", 2, prim_appendContext);
+
+}  // namespace nix