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Auto merge of #14106 - Eh2406:build_feature_map, r=ehuss
Simplify checking feature syntax ### What does this PR try to resolve? Similar to #14089, in my PubGrub work I had to try to understand the `build_feature_map` code that determines if the name refers to a feature or an optional dependency. There were a couple of little things I wanted to clean up while I was staring at the code. Specifically: - there was a lot of vertical space taken up with arguments to `bail` that could be in line at the format string. - some match statements were used where a named helper method would be clearer. - `split_once` could replace a `find ... split_at` dance. - in `dep_map` we were constructing a full `Vec<Dependency>`, when we only cared about whether there was any dependency and whether any of the dependencies were optional. ### How should we test and review this PR? It's an internal re-factor, and the tests still pass. ### Additional information If you're having questions about this code while you're reviewing, this would be a perfect opportunity for better naming and comments. Please ask questions. `@epage:` After this PR I am likely to copy this code into my pubgrub tester. Are there other users who might be interested in looking at a cargo.toml or an index entry and determining what feature names are available and what dependencies they enable? If so maybe this function should be moved to one of the new stable-ish reusable libraries.
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‎src/cargo/core/summary.rs

Lines changed: 54 additions & 95 deletions
Original file line numberDiff line numberDiff line change
@@ -156,13 +156,12 @@ fn build_feature_map(
156156
dependencies: &[Dependency],
157157
) -> CargoResult<FeatureMap> {
158158
use self::FeatureValue::*;
159-
let mut dep_map = HashMap::new();
159+
// A map of dependency names to whether there are any that are optional.
160+
let mut dep_map: HashMap<InternedString, bool> = HashMap::new();
160161
for dep in dependencies.iter() {
161-
dep_map
162-
.entry(dep.name_in_toml())
163-
.or_insert_with(Vec::new)
164-
.push(dep);
162+
*dep_map.entry(dep.name_in_toml()).or_insert(false) |= dep.is_optional();
165163
}
164+
let dep_map = dep_map; // We are done mutating this variable
166165

167166
let mut map: FeatureMap = features
168167
.iter()
@@ -180,117 +179,78 @@ fn build_feature_map(
180179
let explicitly_listed: HashSet<_> = map
181180
.values()
182181
.flatten()
183-
.filter_map(|fv| match fv {
184-
Dep { dep_name } => Some(*dep_name),
185-
_ => None,
186-
})
182+
.filter_map(|fv| fv.explicit_dep_name())
187183
.collect();
188184
for dep in dependencies {
189185
if !dep.is_optional() {
190186
continue;
191187
}
192-
let dep_name_in_toml = dep.name_in_toml();
193-
if features.contains_key(&dep_name_in_toml) || explicitly_listed.contains(&dep_name_in_toml)
194-
{
188+
let dep_name = dep.name_in_toml();
189+
if features.contains_key(&dep_name) || explicitly_listed.contains(&dep_name) {
195190
continue;
196191
}
197-
let fv = Dep {
198-
dep_name: dep_name_in_toml,
199-
};
200-
map.insert(dep_name_in_toml, vec![fv]);
192+
map.insert(dep_name, vec![Dep { dep_name }]);
201193
}
194+
let map = map; // We are done mutating this variable
202195

203196
// Validate features are listed properly.
204197
for (feature, fvs) in &map {
205198
FeatureName::new(feature)?;
206199
for fv in fvs {
207200
// Find data for the referenced dependency...
208-
let dep_data = {
209-
match fv {
210-
Feature(dep_name) | Dep { dep_name, .. } | DepFeature { dep_name, .. } => {
211-
dep_map.get(dep_name)
212-
}
213-
}
214-
};
215-
let is_optional_dep = dep_data
216-
.iter()
217-
.flat_map(|d| d.iter())
218-
.any(|d| d.is_optional());
201+
let dep_data = dep_map.get(&fv.feature_or_dep_name());
219202
let is_any_dep = dep_data.is_some();
203+
let is_optional_dep = dep_data.is_some_and(|&o| o);
220204
match fv {
221205
Feature(f) => {
222206
if !features.contains_key(f) {
223207
if !is_any_dep {
224208
bail!(
225-
"feature `{}` includes `{}` which is neither a dependency \
226-
nor another feature",
227-
feature,
228-
fv
229-
);
209+
"feature `{feature}` includes `{fv}` which is neither a dependency \
210+
nor another feature"
211+
);
230212
}
231213
if is_optional_dep {
232214
if !map.contains_key(f) {
233215
bail!(
234-
"feature `{}` includes `{}`, but `{}` is an \
216+
"feature `{feature}` includes `{fv}`, but `{f}` is an \
235217
optional dependency without an implicit feature\n\
236-
Use `dep:{}` to enable the dependency.",
237-
feature,
238-
fv,
239-
f,
240-
f
218+
Use `dep:{f}` to enable the dependency."
241219
);
242220
}
243221
} else {
244-
bail!("feature `{}` includes `{}`, but `{}` is not an optional dependency\n\
222+
bail!("feature `{feature}` includes `{fv}`, but `{f}` is not an optional dependency\n\
245223
A non-optional dependency of the same name is defined; \
246-
consider adding `optional = true` to its definition.",
247-
feature, fv, f);
224+
consider adding `optional = true` to its definition.");
248225
}
249226
}
250227
}
251228
Dep { dep_name } => {
252229
if !is_any_dep {
253-
bail!(
254-
"feature `{}` includes `{}`, but `{}` is not listed as a dependency",
255-
feature,
256-
fv,
257-
dep_name
258-
);
230+
bail!("feature `{feature}` includes `{fv}`, but `{dep_name}` is not listed as a dependency");
259231
}
260232
if !is_optional_dep {
261233
bail!(
262-
"feature `{}` includes `{}`, but `{}` is not an optional dependency\n\
234+
"feature `{feature}` includes `{fv}`, but `{dep_name}` is not an optional dependency\n\
263235
A non-optional dependency of the same name is defined; \
264-
consider adding `optional = true` to its definition.",
265-
feature,
266-
fv,
267-
dep_name
236+
consider adding `optional = true` to its definition."
268237
);
269238
}
270239
}
271240
DepFeature {
272241
dep_name,
273242
dep_feature,
274243
weak,
275-
..
276244
} => {
277245
// Early check for some unlikely syntax.
278246
if dep_feature.contains('/') {
279-
bail!(
280-
"multiple slashes in feature `{}` (included by feature `{}`) are not allowed",
281-
fv,
282-
feature
283-
);
247+
bail!("multiple slashes in feature `{fv}` (included by feature `{feature}`) are not allowed");
284248
}
285249

286250
// dep: cannot be combined with /
287251
if let Some(stripped_dep) = dep_name.strip_prefix("dep:") {
288252
let has_other_dep = explicitly_listed.contains(stripped_dep);
289-
let is_optional = dep_map
290-
.get(stripped_dep)
291-
.iter()
292-
.flat_map(|d| d.iter())
293-
.any(|d| d.is_optional());
253+
let is_optional = dep_map.get(stripped_dep).is_some_and(|&o| o);
294254
let extra_help = if *weak || has_other_dep || !is_optional {
295255
// In this case, the user should just remove dep:.
296256
// Note that "hiding" an optional dependency
@@ -314,18 +274,14 @@ fn build_feature_map(
314274

315275
// Validation of the feature name will be performed in the resolver.
316276
if !is_any_dep {
317-
bail!(
318-
"feature `{}` includes `{}`, but `{}` is not a dependency",
319-
feature,
320-
fv,
321-
dep_name
322-
);
277+
bail!("feature `{feature}` includes `{fv}`, but `{dep_name}` is not a dependency");
323278
}
324279
if *weak && !is_optional_dep {
325-
bail!("feature `{}` includes `{}` with a `?`, but `{}` is not an optional dependency\n\
280+
bail!(
281+
"feature `{feature}` includes `{fv}` with a `?`, but `{dep_name}` is not an optional dependency\n\
326282
A non-optional dependency of the same name is defined; \
327-
consider removing the `?` or changing the dependency to be optional",
328-
feature, fv, dep_name);
283+
consider removing the `?` or changing the dependency to be optional"
284+
);
329285
}
330286
}
331287
}
@@ -341,15 +297,13 @@ fn build_feature_map(
341297
_ => None,
342298
})
343299
.collect();
344-
if let Some(dep) = dependencies
300+
if let Some((dep, _)) = dep_map
345301
.iter()
346-
.find(|dep| dep.is_optional() && !used.contains(&dep.name_in_toml()))
302+
.find(|&(dep, &is_optional)| is_optional && !used.contains(dep))
347303
{
348304
bail!(
349-
"optional dependency `{}` is not included in any feature\n\
350-
Make sure that `dep:{}` is included in one of features in the [features] table.",
351-
dep.name_in_toml(),
352-
dep.name_in_toml(),
305+
"optional dependency `{dep}` is not included in any feature\n\
306+
Make sure that `dep:{dep}` is included in one of features in the [features] table."
353307
);
354308
}
355309

@@ -376,19 +330,13 @@ pub enum FeatureValue {
376330

377331
impl FeatureValue {
378332
pub fn new(feature: InternedString) -> FeatureValue {
379-
match feature.find('/') {
380-
Some(pos) => {
381-
let (dep, dep_feat) = feature.split_at(pos);
382-
let dep_feat = &dep_feat[1..];
383-
let (dep, weak) = if let Some(dep) = dep.strip_suffix('?') {
384-
(dep, true)
385-
} else {
386-
(dep, false)
387-
};
333+
match feature.split_once('/') {
334+
Some((dep, dep_feat)) => {
335+
let dep_name = dep.strip_suffix('?');
388336
FeatureValue::DepFeature {
389-
dep_name: InternedString::new(dep),
337+
dep_name: InternedString::new(dep_name.unwrap_or(dep)),
390338
dep_feature: InternedString::new(dep_feat),
391-
weak,
339+
weak: dep_name.is_some(),
392340
}
393341
}
394342
None => {
@@ -403,25 +351,36 @@ impl FeatureValue {
403351
}
404352
}
405353

406-
/// Returns `true` if this feature explicitly used `dep:` syntax.
407-
pub fn has_dep_prefix(&self) -> bool {
408-
matches!(self, FeatureValue::Dep { .. })
354+
/// Returns the name of the dependency if and only if it was explicitly named with the `dep:` syntax.
355+
fn explicit_dep_name(&self) -> Option<InternedString> {
356+
match self {
357+
FeatureValue::Dep { dep_name, .. } => Some(*dep_name),
358+
_ => None,
359+
}
360+
}
361+
362+
fn feature_or_dep_name(&self) -> InternedString {
363+
match self {
364+
FeatureValue::Feature(dep_name)
365+
| FeatureValue::Dep { dep_name, .. }
366+
| FeatureValue::DepFeature { dep_name, .. } => *dep_name,
367+
}
409368
}
410369
}
411370

412371
impl fmt::Display for FeatureValue {
413372
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
414373
use self::FeatureValue::*;
415374
match self {
416-
Feature(feat) => write!(f, "{}", feat),
417-
Dep { dep_name } => write!(f, "dep:{}", dep_name),
375+
Feature(feat) => write!(f, "{feat}"),
376+
Dep { dep_name } => write!(f, "dep:{dep_name}"),
418377
DepFeature {
419378
dep_name,
420379
dep_feature,
421380
weak,
422381
} => {
423382
let weak = if *weak { "?" } else { "" };
424-
write!(f, "{}{}/{}", dep_name, weak, dep_feature)
383+
write!(f, "{dep_name}{weak}/{dep_feature}")
425384
}
426385
}
427386
}

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