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C API: nix_get_string now accepts a callback to return the value

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This commit is contained in:
José Luis Lafuente 2024-04-15 21:05:52 +02:00
parent 74e4bc9b1d
commit c75b143b6c
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GPG Key ID: 8A3455EBE455489A
6 changed files with 65 additions and 35 deletions
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37
doc/external-api/README.md
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@ -40,24 +40,37 @@ Nix expression `builtins.nixVersion`.
#include <nix_api_expr.h>
#include <nix_api_value.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// NOTE: This example lacks all error handling. Production code must check for
// errors, as some return values will be undefined.
int main() {
nix_libexpr_init(NULL);
Store* store = nix_store_open(NULL, "dummy://", NULL);
EvalState* state = nix_state_create(NULL, NULL, store); // empty search path (NIX_PATH)
Value *value = nix_alloc_value(NULL, state);
void my_get_string_cb(const char * start, unsigned int n, char ** user_data)
{
*user_data = strdup(start);
}
nix_expr_eval_from_string(NULL, state, "builtins.nixVersion", ".", value);
nix_value_force(NULL, state, value);
printf("Nix version: %s\n", nix_get_string(NULL, value));
int main()
{
nix_libexpr_init(NULL);
nix_gc_decref(NULL, value);
nix_state_free(state);
nix_store_free(store);
return 0;
Store * store = nix_store_open(NULL, "dummy://", NULL);
EvalState * state = nix_state_create(NULL, NULL, store); // empty search path (NIX_PATH)
Value * value = nix_alloc_value(NULL, state);
nix_expr_eval_from_string(NULL, state, "builtins.nixVersion", ".", value);
nix_value_force(NULL, state, value);
char * version;
nix_get_string(NULL, value, my_get_string_cb, version);
printf("Nix version: %s\n", version);
free(version);
nix_gc_decref(NULL, value);
nix_state_free(state);
nix_store_free(store);
return 0;
}
```

12
src/libexpr-c/nix_api_value.cc
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@ -15,9 +15,9 @@
#include "value/context.hh"
#ifdef HAVE_BOEHMGC
# include "gc/gc.h"
# define GC_INCLUDE_NEW 1
# include "gc_cpp.h"
# include "gc/gc.h"
# define GC_INCLUDE_NEW 1
# include "gc_cpp.h"
#endif
// Helper function to throw an exception if value is null
@ -166,16 +166,16 @@ bool nix_get_bool(nix_c_context * context, const Value * value)
NIXC_CATCH_ERRS_RES(false);
}
const char * nix_get_string(nix_c_context * context, const Value * value)
nix_err nix_get_string(nix_c_context * context, const Value * value, nix_get_string_callback callback, void * user_data)
{
if (context)
context->last_err_code = NIX_OK;
try {
auto & v = check_value_not_null(value);
assert(v.type() == nix::nString);
return v.c_str();
call_nix_get_string_callback(v.c_str(), callback, user_data);
}
NIXC_CATCH_ERRS_NULL
NIXC_CATCH_ERRS
}
const char * nix_get_path_string(nix_c_context * context, const Value * value)

8
src/libexpr-c/nix_api_value.h
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@ -178,10 +178,13 @@ bool nix_get_bool(nix_c_context * context, const Value * value);
*
* @param[out] context Optional, stores error information
* @param[in] value Nix value to inspect
* @param[in] callback Called with the string value.
* @param[in] user_data optional, arbitrary data, passed to the callback when it's called.
* @return string
* @return NULL in case of error.
* @return error code, NIX_OK on success.
*/
const char * nix_get_string(nix_c_context * context, const Value * value);
nix_err
nix_get_string(nix_c_context * context, const Value * value, nix_get_string_callback callback, void * user_data);
/** @brief Get path as string
* @param[out] context Optional, stores error information
@ -482,7 +485,6 @@ const StorePath * nix_realised_string_get_store_path(nix_realised_string * reali
*/
void nix_realised_string_free(nix_realised_string * realised_string);
// cffi end
#ifdef __cplusplus
}

20
tests/unit/libexpr/nix_api_expr.cc
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@ -17,9 +17,10 @@ TEST_F(nix_api_expr_test, nix_expr_eval_from_string)
{
nix_expr_eval_from_string(nullptr, state, "builtins.nixVersion", ".", value);
nix_value_force(nullptr, state, value);
auto result = nix_get_string(nullptr, value);
std::string result;
nix_get_string(nullptr, value, OBSERVE_STRING(result));
ASSERT_STREQ(PACKAGE_VERSION, result);
ASSERT_STREQ(PACKAGE_VERSION, result.c_str());
}
TEST_F(nix_api_expr_test, nix_expr_eval_add_numbers)
@ -47,7 +48,8 @@ TEST_F(nix_api_expr_test, nix_expr_eval_drv)
nix_value_call(ctx, stateResult, valueFn, value, valueResult);
ASSERT_EQ(NIX_TYPE_STRING, nix_get_type(nullptr, valueResult));
std::string p = nix_get_string(nullptr, valueResult);
std::string p;
nix_get_string(nullptr, valueResult, OBSERVE_STRING(p));
std::string pEnd = "-myname";
ASSERT_EQ(pEnd, p.substr(p.size() - pEnd.size()));
@ -69,7 +71,8 @@ TEST_F(nix_api_expr_test, nix_build_drv)
nix_expr_eval_from_string(nullptr, state, expr, ".", value);
Value * drvPathValue = nix_get_attr_byname(nullptr, value, state, "drvPath");
const char * drvPath = nix_get_string(nullptr, drvPathValue);
std::string drvPath;
nix_get_string(nullptr, drvPathValue, OBSERVE_STRING(drvPath));
std::string p = drvPath;
std::string pEnd = "-myname.drv";
@ -78,18 +81,19 @@ TEST_F(nix_api_expr_test, nix_build_drv)
// NOTE: .drvPath should be usually be ignored. Output paths are more versatile.
// See https://github.com/NixOS/nix/issues/6507
// Use e.g. nix_string_realise to realise the output.
StorePath * drvStorePath = nix_store_parse_path(ctx, store, drvPath);
StorePath * drvStorePath = nix_store_parse_path(ctx, store, drvPath.c_str());
ASSERT_EQ(true, nix_store_is_valid_path(ctx, store, drvStorePath));
Value * outPathValue = nix_get_attr_byname(ctx, value, state, "outPath");
const char * outPath = nix_get_string(ctx, outPathValue);
std::string outPath;
nix_get_string(ctx, outPathValue, OBSERVE_STRING(outPath));
p = outPath;
pEnd = "-myname";
ASSERT_EQ(pEnd, p.substr(p.size() - pEnd.size()));
ASSERT_EQ(true, drvStorePath->path.isDerivation());
StorePath * outStorePath = nix_store_parse_path(ctx, store, outPath);
StorePath * outStorePath = nix_store_parse_path(ctx, store, outPath.c_str());
ASSERT_EQ(false, nix_store_is_valid_path(ctx, store, outStorePath));
nix_store_realise(ctx, store, drvStorePath, nullptr, nullptr);
@ -142,7 +146,7 @@ TEST_F(nix_api_expr_test, nix_expr_realise_context)
}}
a path: ${builtins.toFile "just-a-file" "ooh file good"}
a derivation path by itself: ${
builtins.unsafeDiscardOutputDependency
builtins.unsafeDiscardOutputDependency
(derivation {
name = "not-actually-built-yet";
system = builtins.currentSystem;

7
tests/unit/libexpr/nix_api_external.cc
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@ -6,7 +6,9 @@
#include "nix_api_expr_internal.h"
#include "nix_api_value.h"
#include "nix_api_external.h"
#include "tests/nix_api_expr.hh"
#include "tests/string_callback.hh"
#include <gtest/gtest.h>
@ -58,6 +60,9 @@ TEST_F(nix_api_expr_test, nix_expr_eval_external)
nix_value_call(ctx, state, valueFn, value, valueResult);
ASSERT_STREQ("nix-external<MyExternalValueDesc( 42 )>", nix_get_string(nullptr, valueResult));
std::string string_value;
nix_get_string(nullptr, valueResult, OBSERVE_STRING(string_value));
ASSERT_STREQ("nix-external<MyExternalValueDesc( 42 )>", string_value.c_str());
}
}

16
tests/unit/libexpr/nix_api_value.cc
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@ -6,6 +6,7 @@
#include "nix_api_value.h"
#include "tests/nix_api_expr.hh"
#include "tests/string_callback.hh"
#include <cstdlib>
#include <gtest/gtest.h>
@ -53,13 +54,15 @@ TEST_F(nix_api_expr_test, nix_value_set_get_bool)
TEST_F(nix_api_expr_test, nix_value_set_get_string)
{
ASSERT_EQ(nullptr, nix_get_string(ctx, nullptr));
ASSERT_DEATH(nix_get_string(ctx, value), "");
std::string string_value;
ASSERT_EQ(NIX_ERR_UNKNOWN, nix_get_string(ctx, nullptr, OBSERVE_STRING(string_value)));
ASSERT_DEATH(nix_get_string(ctx, value, OBSERVE_STRING(string_value)), "");
const char * myString = "some string";
nix_init_string(ctx, value, myString);
ASSERT_STREQ(myString, nix_get_string(ctx, value));
nix_get_string(ctx, value, OBSERVE_STRING(string_value));
ASSERT_STREQ(myString, string_value.c_str());
ASSERT_STREQ("a string", nix_get_typename(ctx, value));
ASSERT_EQ(NIX_TYPE_STRING, nix_get_type(ctx, value));
}
@ -162,11 +165,14 @@ TEST_F(nix_api_expr_test, nix_build_and_init_attr)
ASSERT_EQ(false, nix_has_attr_byname(ctx, value, state, "no-value"));
out_value = nix_get_attr_byname(ctx, value, state, "b");
ASSERT_STREQ("foo", nix_get_string(ctx, out_value));
std::string string_value;
nix_get_string(ctx, out_value, OBSERVE_STRING(string_value));
ASSERT_STREQ("foo", string_value.c_str());
nix_gc_decref(nullptr, out_value);
out_value = nix_get_attr_byidx(ctx, value, state, 1, out_name);
ASSERT_STREQ("foo", nix_get_string(ctx, out_value));
nix_get_string(ctx, out_value, OBSERVE_STRING(string_value));
ASSERT_STREQ("foo", string_value.c_str());
ASSERT_STREQ("b", *out_name);
nix_gc_decref(nullptr, out_value);