1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
|
#include "primops.hh"
#include "store-api.hh"
#include "make-content-addressed.hh"
#include "url.hh"
namespace nix {
/**
* Handler for the content addressed case.
*
* @param state The evaluator state and store to write to.
* @param fromStore The store containing the path to rewrite.
* @param fromPath The source path to be rewritten.
* @param toPathMaybe The path to write the rewritten path to. If empty, the error shows the actual path.
* @param v The return `Value`
*/
static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, const std::optional<StorePath> & toPathMaybe, Value &v) {
// establish toPath or throw
if (!toPathMaybe || !state.store->isValidPath(*toPathMaybe)) {
auto rewrittenPath = makeContentAddressed(fromStore, *state.store, fromPath);
if (toPathMaybe && *toPathMaybe != rewrittenPath)
throw Error({
.msg = hintfmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected",
state.store->printStorePath(fromPath),
state.store->printStorePath(rewrittenPath),
state.store->printStorePath(*toPathMaybe)),
.errPos = state.positions[pos]
});
if (!toPathMaybe)
throw Error({
.msg = hintfmt(
"rewriting '%s' to content-addressed form yielded '%s'; "
"please set this in the 'toPath' attribute passed to 'fetchClosure'",
state.store->printStorePath(fromPath),
state.store->printStorePath(rewrittenPath)),
.errPos = state.positions[pos]
});
}
auto toPath = *toPathMaybe;
// check and return
auto resultInfo = state.store->queryPathInfo(toPath);
if (!resultInfo->isContentAddressed(*state.store)) {
// We don't perform the rewriting when outPath already exists, as an optimisation.
// However, we can quickly detect a mistake if the toPath is input addressed.
throw Error({
.msg = hintfmt("The 'toPath' value '%s' is input addressed, so it can't possibly be the result of rewriting. You may set 'toPath' to an empty string to figure out the correct path.",
state.store->printStorePath(toPath)),
.errPos = state.positions[pos]
});
}
state.mkStorePathString(toPath, v);
}
/**
* Fetch the closure and make sure it's content addressed.
*/
static void runFetchClosureWithContentAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) {
if (!state.store->isValidPath(fromPath))
copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath });
auto info = state.store->queryPathInfo(fromPath);
if (!info->isContentAddressed(*state.store)) {
throw Error({
.msg = hintfmt("The 'fromPath' value '%s' is input addressed, but input addressing was not requested. If you do intend to return an input addressed store path, add 'inputAddressed = true;' to the 'fetchClosure' arguments. Note that content addressing does not require users to configure a trusted binary cache public key on their systems, and is therefore preferred.",
state.store->printStorePath(fromPath)),
.errPos = state.positions[pos]
});
}
state.mkStorePathString(fromPath, v);
}
/**
* Fetch the closure and make sure it's input addressed.
*/
static void runFetchClosureWithInputAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) {
if (!state.store->isValidPath(fromPath))
copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath });
auto info = state.store->queryPathInfo(fromPath);
if (info->isContentAddressed(*state.store)) {
throw Error({
.msg = hintfmt("The 'fetchClosure' result, '%s' is not input addressed, despite 'inputAddressed' being set to true. It is preferable to return a content addressed path, so remove the 'inputAddressed' attribute to ensure content addressing is used in the future",
state.store->printStorePath(fromPath)),
.errPos = state.positions[pos]
});
}
state.mkStorePathString(fromPath, v);
}
typedef std::optional<StorePath> StorePathOrGap;
static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
state.forceAttrs(*args[0], pos, "while evaluating the argument passed to builtins.fetchClosure");
std::optional<std::string> fromStoreUrl;
std::optional<StorePath> fromPath;
std::optional<StorePathOrGap> toPath;
std::optional<bool> inputAddressedMaybe;
for (auto & attr : *args[0]->attrs) {
const auto & attrName = state.symbols[attr.name];
auto attrHint = [&]() -> std::string {
return "while evaluating the '" + attrName + "' attribute passed to builtins.fetchClosure";
};
if (attrName == "fromPath") {
NixStringContext context;
fromPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint());
}
else if (attrName == "toPath") {
state.forceValue(*attr.value, attr.pos);
bool isEmptyString = attr.value->type() == nString && attr.value->string.s == std::string("");
if (isEmptyString) {
toPath = StorePathOrGap {};
}
else {
NixStringContext context;
toPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint());
}
}
else if (attrName == "fromStore")
fromStoreUrl = state.forceStringNoCtx(*attr.value, attr.pos,
attrHint());
else if (attrName == "inputAddressed")
inputAddressedMaybe = state.forceBool(*attr.value, attr.pos, attrHint());
else
throw Error({
.msg = hintfmt("attribute '%s' isn't supported in call to 'fetchClosure'", attrName),
.errPos = state.positions[pos]
});
}
if (!fromPath)
throw Error({
.msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromPath"),
.errPos = state.positions[pos]
});
bool inputAddressed = inputAddressedMaybe.value_or(false);
if (inputAddressed) {
if (toPath)
throw Error({
.msg = hintfmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them",
"inputAddressed",
"toPath"),
.errPos = state.positions[pos]
});
}
if (!fromStoreUrl)
throw Error({
.msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"),
.errPos = state.positions[pos]
});
auto parsedURL = parseURL(*fromStoreUrl);
if (parsedURL.scheme != "http" &&
parsedURL.scheme != "https" &&
!(getEnv("_NIX_IN_TEST").has_value() && parsedURL.scheme == "file"))
throw Error({
.msg = hintfmt("'fetchClosure' only supports http:// and https:// stores"),
.errPos = state.positions[pos]
});
if (!parsedURL.query.empty())
throw Error({
.msg = hintfmt("'fetchClosure' does not support URL query parameters (in '%s')", *fromStoreUrl),
.errPos = state.positions[pos]
});
auto fromStore = openStore(parsedURL.to_string());
if (toPath)
runFetchClosureWithRewrite(state, pos, *fromStore, *fromPath, *toPath, v);
else if (inputAddressed)
runFetchClosureWithInputAddressedPath(state, pos, *fromStore, *fromPath, v);
else
runFetchClosureWithContentAddressedPath(state, pos, *fromStore, *fromPath, v);
}
static RegisterPrimOp primop_fetchClosure({
.name = "__fetchClosure",
.args = {"args"},
.doc = R"(
Fetch a Nix store closure from a binary cache.
This function can be used in three ways:
- Fetch any store path and rewrite it to a fully content-addressed store path. Example:
```nix
builtins.fetchClosure {
fromStore = "https://cache.nixos.org";
fromPath = /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1;
toPath = /nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1;
}
```
- Fetch a content-addressed store path.
```nix
builtins.fetchClosure {
fromStore = "https://cache.nixos.org";
fromPath = /nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1;
}
```
- Fetch an [input-addressed store path](@docroot@/glossary.md#gloss-input-addressed-store-object) as is. This depends on user configuration, which is less preferable.
```nix
builtins.fetchClosure {
fromStore = "https://cache.nixos.org";
fromPath = /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1;
inputAddressed = true;
}
```
**Rewriting a store path**
This first example fetches `/nix/store/r2jd...` from the specified binary cache,
and rewrites it into the content-addressed store path
`/nix/store/ldbh...`.
By rewriting the store paths, you can add the contents to any store without requiring that you or perhaps your users configure any extra trust.
To find out the correct value for `toPath` given a `fromPath`,
you can use [`nix store make-content-addressed`](@docroot@/command-ref/new-cli/nix3-store-make-content-addressed.md):
```console
# nix store make-content-addressed --from https://cache.nixos.org /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1
rewrote '/nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1' to '/nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1'
```
Alternatively, you may set `toPath = ""` and find the correct `toPath` in the error message.
**Not rewriting**
`toPath` may be omitted when either
- `fromPath` is already content-addressed, or
- `inputAddressed = true;` is set.
Fetching an [input addressed path](@docroot@/glossary.md#gloss-input-addressed-store-object) is not recommended because it requires that the source be trusted by the Nix configuration.
**`builtins.storePath`**
This function is similar to [`builtins.storePath`](#builtins-storePath) in that it
allows you to use a previously built store path in a Nix
expression. However, it is more reproducible because it requires
specifying a binary cache from which the path can be fetched.
Also, the default requirement of a content-addressed final store path
avoids the need for users to configure [`trusted-public-keys`](@docroot@/command-ref/conf-file.md#conf-trusted-public-keys).
**Experimental feature**
This function is only available if you enable the experimental
feature `fetch-closure`.
)",
.fun = prim_fetchClosure,
.experimentalFeature = Xp::FetchClosure,
});
}
|
