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
|
use std::path::Path;
use std::sync::OnceLock;
/// Returns the default feature name configured in the consuming crate's
/// `Cargo.toml` under `[package.metadata.might_be_async.default_feature_name]`.
///
/// If the metadata key is absent or unreadable, falls back to `"async"`.
pub(crate) fn default_feature_name() -> &'static str {
static DEFAULT: OnceLock<String> = OnceLock::new();
DEFAULT.get_or_init(read_default_feature_name)
}
fn read_default_feature_name() -> String {
let manifest_dir = match std::env::var("CARGO_MANIFEST_DIR") {
Ok(dir) => dir,
Err(_) => return "async".to_string(),
};
let cargo_toml_path = Path::new(&manifest_dir).join("Cargo.toml");
let content = match std::fs::read_to_string(cargo_toml_path) {
Ok(c) => c,
Err(_) => return "async".to_string(),
};
parse_feature_name_from_toml(&content).unwrap_or_else(|| "async".to_string())
}
/// Pure function: parse `default_feature_name` from TOML content.
/// Returns `None` if the key is missing, unreadable, or not a string.
fn parse_feature_name_from_toml(content: &str) -> Option<String> {
let value: toml::Value = content.parse().ok()?;
value
.get("package")
.and_then(|p| p.get("metadata"))
.and_then(|m| m.get("might_be_async"))
.and_then(|a| a.get("default_feature_name"))
.and_then(|v| v.as_str())
.map(|s| s.to_string())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn parses_custom_feature_name() {
let toml = r#"
[package]
[package.metadata.might_be_async]
default_feature_name = "my_async"
"#;
assert_eq!(
parse_feature_name_from_toml(toml),
Some("my_async".to_string())
);
}
#[test]
fn missing_metadata_returns_none() {
let toml = "[package]\nname = \"foo\"\n";
assert_eq!(parse_feature_name_from_toml(toml), None);
}
#[test]
fn missing_might_be_async_section_returns_none() {
let toml = r#"
[package]
[package.metadata]
some_other_key = "value"
"#;
assert_eq!(parse_feature_name_from_toml(toml), None);
}
#[test]
fn empty_string_returns_none() {
assert_eq!(parse_feature_name_from_toml(""), None);
}
#[test]
fn invalid_toml_returns_none() {
assert_eq!(parse_feature_name_from_toml("not valid toml {{"), None);
}
#[test]
fn value_is_not_string_returns_none() {
let toml = r#"
[package.metadata.might_be_async]
default_feature_name = 42
"#;
assert_eq!(parse_feature_name_from_toml(toml), None);
}
#[test]
fn env_default_returns_foo_async() {
// In `cargo test`, CARGO_MANIFEST_DIR is set to this crate's directory,
// whose Cargo.toml has `default_feature_name = "foo_async"`.
assert_eq!(default_feature_name(), "foo_async");
}
}
|
