Add error context for most basic coercions

4 files changed, 18 insertions, 22 deletions

diff --git a/src/libexpr/primops/context.cc b/src/libexpr/primops/context.cc
index 3701bd442..f1feb4dc6 100644
--- a/src/libexpr/primops/context.cc
+++ b/src/libexpr/primops/context.cc
@@ -17,7 +17,7 @@ static RegisterPrimOp primop_unsafeDiscardStringContext("__unsafeDiscardStringCo
 static void prim_hasContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    state.forceString(*args[0], context, pos);
+    state.forceString(*args[0], context, pos, "While evaluating the argument passed to builtins.hasContext");
     v.mkBool(!context.empty());
 }
 
@@ -72,7 +72,7 @@ static void prim_getContext(EvalState & state, const Pos & pos, Value * * args,
         Strings outputs;
     };
     PathSet context;
-    state.forceString(*args[0], context, pos);
+    state.forceString(*args[0], context, pos, "While evaluating the argument passed to builtins.getContext");
     auto contextInfos = std::map<Path, ContextInfo>();
     for (const auto & p : context) {
         Path drv;
@@ -136,9 +136,9 @@ static RegisterPrimOp primop_getContext("__getContext", 1, prim_getContext);
 static void prim_appendContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    auto orig = state.forceString(*args[0], context, pos);
+    auto orig = state.forceString(*args[0], context, pos, "while evaluating the first argument passed to builtins.appendContext");
 
-    state.forceAttrs(*args[1], pos);
+    state.forceAttrs(*args[1], pos, "While evaluating the second argument passed to builtins.appendContext");
 
     auto sPath = state.symbols.create("path");
     auto sAllOutputs = state.symbols.create("allOutputs");
@@ -150,16 +150,16 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
             });
         if (!settings.readOnlyMode)
             state.store->ensurePath(state.store->parseStorePath(i.name));
-        state.forceAttrs(*i.value, *i.pos);
+        state.forceAttrs(*i.value, *i.pos, "While evaluating the value of a string context");
         auto iter = i.value->attrs->find(sPath);
         if (iter != i.value->attrs->end()) {
-            if (state.forceBool(*iter->value, *iter->pos))
+            if (state.forceBool(*iter->value, *iter->pos, "While evaluating the `path` attribute of a string context"))
                 context.insert(i.name);
         }
 
         iter = i.value->attrs->find(sAllOutputs);
         if (iter != i.value->attrs->end()) {
-            if (state.forceBool(*iter->value, *iter->pos)) {
+            if (state.forceBool(*iter->value, *iter->pos, "While evaluating the `allOutputs` attribute of a string context")) {
                 if (!isDerivation(i.name)) {
                     throw EvalError({
                         .msg = hintfmt("Tried to add all-outputs context of %s, which is not a derivation, to a string", i.name),
@@ -172,7 +172,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
 
         iter = i.value->attrs->find(state.sOutputs);
         if (iter != i.value->attrs->end()) {
-            state.forceList(*iter->value, *iter->pos);
+            state.forceList(*iter->value, *iter->pos, "While evaluating the `outputs` attribute of a string context");
             if (iter->value->listSize() && !isDerivation(i.name)) {
                 throw EvalError({
                     .msg = hintfmt("Tried to add derivation output context of %s, which is not a derivation, to a string", i.name),
@@ -180,7 +180,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
                 });
             }
             for (auto elem : iter->value->listItems()) {
-                auto name = state.forceStringNoCtx(*elem, *iter->pos);
+                auto name = state.forceStringNoCtx(*elem, *iter->pos, "While evaluating an output name within a string context");
                 context.insert(concatStrings("!", name, "!", i.name));
             }
         }
diff --git a/src/libexpr/primops/fetchMercurial.cc b/src/libexpr/primops/fetchMercurial.cc
index b7f715859..199f7508e 100644
--- a/src/libexpr/primops/fetchMercurial.cc
+++ b/src/libexpr/primops/fetchMercurial.cc
@@ -19,8 +19,6 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
 
     if (args[0]->type() == nAttrs) {
 
-        state.forceAttrs(*args[0], pos);
-
         for (auto & attr : *args[0]->attrs) {
             std::string_view n(attr.name);
             if (n == "url")
@@ -28,14 +26,14 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
             else if (n == "rev") {
                 // Ugly: unlike fetchGit, here the "rev" attribute can
                 // be both a revision or a branch/tag name.
-                auto value = state.forceStringNoCtx(*attr.value, *attr.pos);
+                auto value = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the `rev` attribute passed to builtins.fetchMercurial");
                 if (std::regex_match(value.begin(), value.end(), revRegex))
                     rev = Hash::parseAny(value, htSHA1);
                 else
                     ref = value;
             }
             else if (n == "name")
-                name = state.forceStringNoCtx(*attr.value, *attr.pos);
+                name = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the `name` attribute passed to builtins.fetchMercurial");
             else
                 throw EvalError({
                     .msg = hintfmt("unsupported argument '%s' to 'fetchMercurial'", attr.name),
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 9c2da2178..a40eddfca 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -102,7 +102,7 @@ static void fetchTree(
     state.forceValue(*args[0], pos);
 
     if (args[0]->type() == nAttrs) {
-        state.forceAttrs(*args[0], pos);
+        state.forceAttrs(*args[0], pos, "While evaluating the argument passed to builtins.fetchTree");
 
         fetchers::Attrs attrs;
 
@@ -112,7 +112,7 @@ static void fetchTree(
                     .msg = hintfmt("unexpected attribute 'type'"),
                     .errPos = pos
                 });
-            type = state.forceStringNoCtx(*aType->value, *aType->pos);
+            type = state.forceStringNoCtx(*aType->value, *aType->pos, "While evaluating the `type` attribute passed to builtins.fetchTree");
         } else if (!type)
             throw Error({
                 .msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
@@ -195,16 +195,14 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
 
     if (args[0]->type() == nAttrs) {
 
-        state.forceAttrs(*args[0], pos);
-
         for (auto & attr : *args[0]->attrs) {
             std::string n(attr.name);
             if (n == "url")
-                url = state.forceStringNoCtx(*attr.value, *attr.pos);
+                url = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the url we should fetch");
             else if (n == "sha256")
-                expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
+                expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the sha256 of the content we should fetch"), htSHA256);
             else if (n == "name")
-                name = state.forceStringNoCtx(*attr.value, *attr.pos);
+                name = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the name of the content we should fetch");
             else
                 throw EvalError({
                     .msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
@@ -218,7 +216,7 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
                 .errPos = pos
             });
     } else
-        url = state.forceStringNoCtx(*args[0], pos);
+        url = state.forceStringNoCtx(*args[0], pos, "While evaluating the url we should fetch");
 
     url = resolveUri(*url);
 
diff --git a/src/libexpr/primops/fromTOML.cc b/src/libexpr/primops/fromTOML.cc
index dd4280030..6bfd8e285 100644
--- a/src/libexpr/primops/fromTOML.cc
+++ b/src/libexpr/primops/fromTOML.cc
@@ -7,7 +7,7 @@ namespace nix {
 
 static void prim_fromTOML(EvalState & state, const Pos & pos, Value * * args, Value & val)
 {
-    auto toml = state.forceStringNoCtx(*args[0], pos);
+    auto toml = state.forceStringNoCtx(*args[0], pos, "While evaluating the argument passed to builtins.fromTOML");
 
     std::istringstream tomlStream(std::string{toml});