diff --git a/doc/manual/rl-next/print-value-in-error-cannot-coerce.md b/doc/manual/rl-next/print-value-in-error-cannot-coerce.md new file mode 100644 index 000000000000..f8873f0dd03c --- /dev/null +++ b/doc/manual/rl-next/print-value-in-error-cannot-coerce.md @@ -0,0 +1,38 @@ +synopsis: Prints the failing value in `error: cannot coerce` messages +issues: #561 +prs: #9553 +description: { + +The `error: cannot coerce a to a string` message now includes the value +which caused the error. This makes debugging much easier: + +``` +$ nix repl nixpkgs +nix-repl> nixpkgs = legacyPackages.x86_64-linux.path +nix-repl> system = { system = "x86_64-linux"; } +nix-repl> import nixpkgs { inherit system; } +error: + … while evaluating a branch condition + + at /nix/store/7g8wbm1z6948x0qma4hzkkb9a3xys76w-source/pkgs/stdenv/booter.nix:64:9: + + 63| go = pred: n: + 64| if n == len + | ^ + 65| then rnul pred + + … while calling the 'length' builtin + + at /nix/store/7g8wbm1z6948x0qma4hzkkb9a3xys76w-source/pkgs/stdenv/booter.nix:62:13: + + 61| let + 62| len = builtins.length list; + | ^ + 63| go = pred: n: + + (stack trace truncated; use '--show-trace' to show the full trace) + + error: cannot coerce a set to a string: { system = "x86_64-linux"; } +``` + +} diff --git a/doc/manual/src/language/string-interpolation.md b/doc/manual/src/language/string-interpolation.md index e999b287b9c6..6e28d26646bc 100644 --- a/doc/manual/src/language/string-interpolation.md +++ b/doc/manual/src/language/string-interpolation.md @@ -189,7 +189,7 @@ If neither is present, an error is thrown. > "${a}" > ``` > -> error: cannot coerce a set to a string +> error: cannot coerce a set to a string: { } > > at «string»:4:2: > diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc index 7e68e6f9b742..b52274b64e1e 100644 --- a/src/libexpr/eval.cc +++ b/src/libexpr/eval.cc @@ -26,9 +26,9 @@ #include #include #include -#include #include #include +#include #include #include @@ -2286,7 +2286,7 @@ BackedStringView EvalState::coerceToString( return std::move(*maybeString); auto i = v.attrs->find(sOutPath); if (i == v.attrs->end()) { - error("cannot coerce %1% to a string", showType(v)) + error("cannot coerce %1% to a string: %2%", showType(v), printValue(*this, v)) .withTrace(pos, errorCtx) .debugThrow(); } @@ -2332,7 +2332,7 @@ BackedStringView EvalState::coerceToString( } } - error("cannot coerce %1% to a string", showType(v)) + error("cannot coerce %1% to a string: %2%", showType(v), printValue(*this, v)) .withTrace(pos, errorCtx) .debugThrow(); } @@ -2691,8 +2691,10 @@ void EvalState::printStatistics() std::string ExternalValueBase::coerceToString(const Pos & pos, NixStringContext & context, bool copyMore, bool copyToStore) const { + std::strstream printed; + print(printed); throw TypeError({ - .msg = hintfmt("cannot coerce %1% to a string", showType()) + .msg = hintfmt("cannot coerce %1% to a string: %2%", showType(), printed.str()) }); } diff --git a/tests/functional/lang/eval-fail-bad-string-interpolation-1.err.exp b/tests/functional/lang/eval-fail-bad-string-interpolation-1.err.exp index eb73e9a52986..e54ecc6d1a73 100644 --- a/tests/functional/lang/eval-fail-bad-string-interpolation-1.err.exp +++ b/tests/functional/lang/eval-fail-bad-string-interpolation-1.err.exp @@ -7,4 +7,4 @@ error: | ^ 2| - error: cannot coerce a function to a string + error: cannot coerce a function to a string: diff --git a/tests/functional/lang/eval-fail-bad-string-interpolation-3.err.exp b/tests/functional/lang/eval-fail-bad-string-interpolation-3.err.exp index ac14f329b787..6f0a96f78dd3 100644 --- a/tests/functional/lang/eval-fail-bad-string-interpolation-3.err.exp +++ b/tests/functional/lang/eval-fail-bad-string-interpolation-3.err.exp @@ -7,4 +7,4 @@ error: | ^ 2| - error: cannot coerce a function to a string + error: cannot coerce a function to a string: diff --git a/tests/unit/libexpr/error_traces.cc b/tests/unit/libexpr/error_traces.cc index 81498f65a3f8..c2403bee938f 100644 --- a/tests/unit/libexpr/error_traces.cc +++ b/tests/unit/libexpr/error_traces.cc @@ -295,7 +295,7 @@ namespace nix { TEST_F(ErrorTraceTest, toPath) { ASSERT_TRACE2("toPath []", TypeError, - hintfmt("cannot coerce %s to a string", "a list"), + hintfmt("cannot coerce %s to a string: %s", "a list", "[ ]"), hintfmt("while evaluating the first argument passed to builtins.toPath")); ASSERT_TRACE2("toPath \"foo\"", @@ -309,7 +309,7 @@ namespace nix { TEST_F(ErrorTraceTest, storePath) { ASSERT_TRACE2("storePath true", TypeError, - hintfmt("cannot coerce %s to a string", "a Boolean"), + hintfmt("cannot coerce %s to a string: %s", "a Boolean", "true"), hintfmt("while evaluating the first argument passed to 'builtins.storePath'")); } @@ -318,7 +318,7 @@ namespace nix { TEST_F(ErrorTraceTest, pathExists) { ASSERT_TRACE2("pathExists []", TypeError, - hintfmt("cannot coerce %s to a string", "a list"), + hintfmt("cannot coerce %s to a string: %s", "a list", "[ ]"), hintfmt("while realising the context of a path")); ASSERT_TRACE2("pathExists \"zorglub\"", @@ -332,7 +332,7 @@ namespace nix { TEST_F(ErrorTraceTest, baseNameOf) { ASSERT_TRACE2("baseNameOf []", TypeError, - hintfmt("cannot coerce %s to a string", "a list"), + hintfmt("cannot coerce %s to a string: %s", "a list", "[ ]"), hintfmt("while evaluating the first argument passed to builtins.baseNameOf")); } @@ -377,7 +377,7 @@ namespace nix { TEST_F(ErrorTraceTest, filterSource) { ASSERT_TRACE2("filterSource [] []", TypeError, - hintfmt("cannot coerce %s to a string", "a list"), + hintfmt("cannot coerce %s to a string: %s", "a list", "[ ]"), hintfmt("while evaluating the second argument (the path to filter) passed to 'builtins.filterSource'")); ASSERT_TRACE2("filterSource [] \"foo\"", @@ -1038,7 +1038,7 @@ namespace nix { TEST_F(ErrorTraceTest, toString) { ASSERT_TRACE2("toString { a = 1; }", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ a = 1; }"), hintfmt("while evaluating the first argument passed to builtins.toString")); } @@ -1057,7 +1057,7 @@ namespace nix { ASSERT_TRACE2("substring 0 3 {}", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating the third argument (the string) passed to builtins.substring")); ASSERT_TRACE1("substring (-3) 3 \"sometext\"", @@ -1070,7 +1070,7 @@ namespace nix { TEST_F(ErrorTraceTest, stringLength) { ASSERT_TRACE2("stringLength {} # TODO: context is missing ???", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating the argument passed to builtins.stringLength")); } @@ -1143,7 +1143,7 @@ namespace nix { ASSERT_TRACE2("concatStringsSep \"foo\" [ 1 2 {} ] # TODO: coerce to string is buggy", TypeError, - hintfmt("cannot coerce %s to a string", "an integer"), + hintfmt("cannot coerce %s to a string: %s", "an integer", "1"), hintfmt("while evaluating one element of the list of strings to concat passed to builtins.concatStringsSep")); } @@ -1229,12 +1229,12 @@ namespace nix { ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = {}; }", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating the attribute 'system' of derivation 'foo'")); ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = {}; }", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating the attribute 'outputs' of derivation 'foo'")); ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"drv\"; }", @@ -1279,17 +1279,17 @@ namespace nix { ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = [ {} ]; }", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating an element of the argument list")); ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; args = [ \"a\" {} ]; }", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating an element of the argument list")); ASSERT_TRACE2("derivationStrict { name = \"foo\"; builder = 1; system = 1; outputs = \"out\"; FOO = {}; }", TypeError, - hintfmt("cannot coerce %s to a string", "a set"), + hintfmt("cannot coerce %s to a string: %s", "a set", "{ }"), hintfmt("while evaluating the attribute 'FOO' of derivation 'foo'")); }