alef 0.25.35

Opinionated polyglot binding generator for Rust libraries
Documentation 
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

use crate::core::ir::{FunctionDef, ParamDef, TypeRef};
use std::collections::BTreeSet;

use super::types::kotlin_type_with_string_imports;
use crate::backends::kotlin::gen_bindings::helpers::emit_cleaned_kdoc;
use crate::backends::kotlin::gen_bindings::shared::to_lower_camel;

pub(crate) fn emit_function(
    f: &FunctionDef,
    out: &mut String,
    imports: &mut BTreeSet<String>,
    _java_package: &str,
    client_type_names: &std::collections::HashSet<&str>,
) {
    emit_cleaned_kdoc(out, &f.doc, "    ");
    let params: Vec<String> = f.params.iter().map(|p| format_param_with_imports(p, imports)).collect();
    let return_ty = kotlin_type_with_string_imports(&f.return_type, false, imports);
    let async_kw = if f.is_async { "suspend " } else { "" };
    let func_name_camel = to_lower_camel(&f.name);
    let call_args = f
        .params
        .iter()
        .map(|p| to_lower_camel(&p.name))
        .collect::<Vec<_>>()
        .join(", ");

    // Detect a client-type return so we can wrap the Java result in its Kotlin
    // companion (e.g. `SampleLlm.createClient(...)` returns Java `DefaultClient`
    // but the Kotlin facade must hand back the coroutine-friendly Kotlin
    // `DefaultClient` wrapper).
    let returns_client_type = match &f.return_type {
        TypeRef::Named(n) => client_type_names.contains(n.as_str()),
        _ => false,
    };

    out.push_str(&crate::backends::kotlin::template_env::render(
        "function_signature.jinja",
        minijinja::context! {
            async_kw => async_kw,
            name => func_name_camel,
            params => params.join(", "),
            return_type => return_ty,
        },
    ));
    out.push('\n');

    // The Java facade returns `Optional<T>` for Rust `Option<T>` returns; the
    // Kotlin facade exposes the friendlier `T?`. Unwrap with `.orElse(null)` so
    // the types line up.
    let optional_suffix = if matches!(f.return_type, TypeRef::Optional(_)) && !returns_client_type {
        ".orElse(null)"
    } else {
        ""
    };

    if f.is_async {
        // The Java facade lowers async Rust functions to blocking calls (it
        // awaits the future internally and returns the resolved value, not a
        // CompletionStage). Wrap the call in `withContext(Dispatchers.IO)` so
        // the suspend function yields the calling thread while the JNI call
        // blocks under it.
        if returns_client_type {
            let wrapper = return_ty.trim_end_matches('?');
            out.push_str(&crate::backends::kotlin::template_env::render(
                "async_bridge_client_return.jinja",
                minijinja::context! {
                    wrapper => wrapper,
                    name => func_name_camel,
                    args => call_args,
                },
            ));
        } else {
            out.push_str(&crate::backends::kotlin::template_env::render(
                "async_bridge_return.jinja",
                minijinja::context! {
                    name => func_name_camel,
                    args => call_args,
                    optional_suffix => optional_suffix,
                },
            ));
        }
    } else if matches!(f.return_type, TypeRef::Unit) {
        out.push_str(&crate::backends::kotlin::template_env::render(
            "bridge_call_unit.jinja",
            minijinja::context! {
                name => func_name_camel,
                args => call_args,
            },
        ));
        out.push('\n');
    } else if returns_client_type {
        let wrapper = return_ty.trim_end_matches('?');
        out.push_str(&crate::backends::kotlin::template_env::render(
            "bridge_client_return.jinja",
            minijinja::context! {
                wrapper => wrapper,
                name => func_name_camel,
                args => call_args,
            },
        ));
    } else {
        out.push_str(&crate::backends::kotlin::template_env::render(
            "bridge_return.jinja",
            minijinja::context! {
                name => func_name_camel,
                args => call_args,
                optional_suffix => optional_suffix,
            },
        ));
    }
    out.push_str("    }\n");
}

// ---------------------------------------------------------------------------
// Parameter formatting
// ---------------------------------------------------------------------------

pub(crate) fn format_param_with_imports(p: &ParamDef, imports: &mut BTreeSet<String>) -> String {
    let ty_str = kotlin_type_with_string_imports(&p.ty, p.optional, imports);
    // Optional params get a `= null` default so callers can drop them via
    // named-argument syntax (e.g. `createClient(apiKey = "x", baseUrl = "y")`)
    // without having to spell out every nullable downstream argument.
    let default = if p.optional { " = null" } else { "" };
    format!("{}: {}{}", to_lower_camel(&p.name), ty_str, default)
}

// ---------------------------------------------------------------------------
// Type-string rendering (String-keyed imports variant — used by JVM + MPP)
// ---------------------------------------------------------------------------