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Merge pull request #9754 from 9999years/print-value-when-coercion-fails

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Print the value in `error: cannot coerce` messages

(cherry picked from commit 5b7bfd2d6b89d7dd5f54c1ca6c8072358d31a84e)

===

test taken from 6e8d5983143ae576e3f4b1d2954a5267f2943a49; it was added
previously (and not backported because its pr was a mostly-revert), but
it's useful to have around.

Change-Id: Icbd14b55e3610ce7b774667bf14b82e6dc717982
This commit is contained in:
eldritch horrors 2024-03-08 05:06:09 +01:00
parent 2f7c3fa251
commit 609a8e0d94
10 changed files with 84 additions and 29 deletions
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24
doc/manual/rl-next/print-value-in-coercion-error.md Normal file
View file

@ -0,0 +1,24 @@
---
synopsis: Coercion errors include the failing value
issues: #561
prs: #9754
---
The `error: cannot coerce a <TYPE> to a string` message now includes the value
which caused the error.
Before:
```
error: cannot coerce a set to a string
```
After:
```
error: cannot coerce a set to a string: { aesSupport = «thunk»;
avx2Support = «thunk»; avx512Support = «thunk»; avxSupport = «thunk»;
canExecute = «thunk»; config = «thunk»; darwinArch = «thunk»; darwinMinVersion
= «thunk»; darwinMinVersionVariable = «thunk»; darwinPlatform = «thunk»; «84
attributes elided»}
```

10
src/libexpr/eval.cc
View file

@ -2279,7 +2279,9 @@ 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),
ValuePrinter(*this, v, errorPrintOptions))
.withTrace(pos, errorCtx)
.debugThrow<TypeError>();
}
@ -2325,7 +2327,9 @@ BackedStringView EvalState::coerceToString(
}
}
error("cannot coerce %1% to a string", showType(v))
error("cannot coerce %1% to a string: %2%",
showType(v),
ValuePrinter(*this, v, errorPrintOptions))
.withTrace(pos, errorCtx)
.debugThrow<TypeError>();
}
@ -2657,7 +2661,7 @@ void EvalState::printStatistics()
std::string ExternalValueBase::coerceToString(const Pos & pos, NixStringContext & context, bool copyMore, bool copyToStore) const
{
throw TypeError({
.msg = hintfmt("cannot coerce %1% to a string", showType())
.msg = hintfmt("cannot coerce %1% to a string: %2%", showType(), *this)
});
}

8
src/libexpr/print-options.hh
View file

@ -36,11 +36,17 @@ struct PrintOptions
*/
size_t maxDepth = std::numeric_limits<size_t>::max();
/**
* Maximum number of attributes in an attribute set to print.
* Maximum number of attributes in attribute sets to print.
*
* Note that this is a limit for the entire print invocation, not for each
* attribute set encountered.
*/
size_t maxAttrs = std::numeric_limits<size_t>::max();
/**
* Maximum number of list items to print.
*
* Note that this is a limit for the entire print invocation, not for each
* list encountered.
*/
size_t maxListItems = std::numeric_limits<size_t>::max();
/**

7
src/libexpr/print.cc
View file

@ -159,6 +159,8 @@ private:
EvalState & state;
PrintOptions options;
std::optional<ValuesSeen> seen;
size_t attrsPrinted = 0;
size_t listItemsPrinted = 0;
void printRepeated()
{
@ -277,7 +279,6 @@ private:
else
std::sort(sorted.begin(), sorted.end(), ImportantFirstAttrNameCmp());
size_t attrsPrinted = 0;
for (auto & i : sorted) {
if (attrsPrinted >= options.maxAttrs) {
printElided(sorted.size() - attrsPrinted, "attribute", "attributes");
@ -305,7 +306,6 @@ private:
output << "[ ";
if (depth < options.maxDepth) {
size_t listItemsPrinted = 0;
for (auto elem : v.listItems()) {
if (listItemsPrinted >= options.maxListItems) {
printElided(v.listSize() - listItemsPrinted, "item", "items");
@ -484,6 +484,9 @@ public:
void print(Value & v)
{
attrsPrinted = 0;
listItemsPrinted = 0;
if (options.trackRepeated) {
seen.emplace();
} else {

2
tests/functional/lang/eval-fail-bad-string-interpolation-1.err.exp
View file

@ -5,4 +5,4 @@ error:
| ^
2|
error: cannot coerce a function to a string
error: cannot coerce a function to a string: «lambda @ /pwd/lang/eval-fail-bad-string-interpolation-1.nix:1:4»

2
tests/functional/lang/eval-fail-bad-string-interpolation-3.err.exp
View file

@ -5,4 +5,4 @@ error:
| ^
2|
error: cannot coerce a function to a string
error: cannot coerce a function to a string: «lambda @ /pwd/lang/eval-fail-bad-string-interpolation-3.nix:1:5»

9
tests/functional/lang/eval-fail-bad-string-interpolation-4.err.exp Normal file
View file

@ -0,0 +1,9 @@
error:
… while evaluating a path segment
at /pwd/lang/eval-fail-bad-string-interpolation-4.nix:9:3:
8| # The error message should not be too long.
9| ''${pkgs}''
| ^
10|
error: cannot coerce a set to a string: { a = { a = { a = { a = "ha"; b = "ha"; c = "ha"; d = "ha"; e = "ha"; f = "ha"; g = "ha"; h = "ha"; j = "ha"; }; «4294967295 attributes elided»}; «4294967294 attributes elided»}; «4294967293 attributes elided»}

9
tests/functional/lang/eval-fail-bad-string-interpolation-4.nix Normal file
View file

@ -0,0 +1,9 @@
let
# Basically a "billion laughs" attack, but toned down to simulated `pkgs`.
ha = x: y: { a = x y; b = x y; c = x y; d = x y; e = x y; f = x y; g = x y; h = x y; j = x y; };
has = ha (ha (ha (ha (x: x)))) "ha";
# A large structure that has already been evaluated.
pkgs = builtins.deepSeq has has;
in
# The error message should not be too long.
''${pkgs}''

28
tests/unit/libexpr/error_traces.cc
View file

@ -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", ANSI_CYAN "true" ANSI_NORMAL),
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 = " ANSI_CYAN "1" ANSI_NORMAL "; }"),
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", ANSI_CYAN "1" ANSI_NORMAL),
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'"));
}