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
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
mod binding_file;
mod constructors;
mod functions;
mod methods;
mod service_api;
pub(super) mod types;
use binding_file::{find_options_bridge_function, format_go_code, gen_go_file, strip_trailing_whitespace};
use crate::core::backend::{Backend, BuildConfig, BuildDependency, Capabilities, GeneratedFile};
use crate::core::config::{AdapterPattern, BridgeBinding, Language, ResolvedCrateConfig, resolve_output_dir};
use crate::core::ir::ApiSurface;
use std::collections::{HashMap, HashSet};
use std::path::PathBuf;
pub struct GoBackend;
impl GoBackend {
/// Extract the package name from module path (last segment).
/// Sanitize by removing hyphens and converting to lowercase.
fn package_name(module_path: &str) -> String {
module_path
.split('/')
.next_back()
.unwrap_or("binding")
.replace('-', "")
.to_lowercase()
}
}
impl Backend for GoBackend {
fn name(&self) -> &str {
"go"
}
fn language(&self) -> Language {
Language::Go
}
fn capabilities(&self) -> Capabilities {
Capabilities {
supports_async: true,
supports_classes: true,
supports_enums: true,
supports_option: true,
supports_result: true,
supports_service_api: true,
..Capabilities::default()
}
}
fn generate_bindings(&self, api: &ApiSurface, config: &ResolvedCrateConfig) -> anyhow::Result<Vec<GeneratedFile>> {
let module_path = config.go_module();
let pkg_name = config
.go
.as_ref()
.and_then(|g| g.package_name.clone())
.unwrap_or_else(|| Self::package_name(&module_path));
let ffi_prefix = config.ffi_prefix();
let output_dir = {
let mut d = resolve_output_dir(config.output_paths.get("go"), &config.name, "packages/go/");
if !d.ends_with('/') {
d.push('/');
}
d
};
let ffi_lib_name = config.ffi_lib_name();
let ffi_header = config.ffi_header_name();
// Derive the FFI crate directory from the configured output path.
let ffi_crate_dir = config
.output_paths
.get("ffi")
.and_then(|p| {
let path = p.as_path();
path.ancestors()
.find(|a| {
a.file_name()
.is_some_and(|n| n != "src" && n != "lib" && n != "include")
})
.map(|a| a.to_string_lossy().to_string())
})
.unwrap_or_else(|| format!("crates/{ffi_lib_name}"));
// Collect bridge param names from trait_bridges config so we can strip them
// from generated function signatures and emit ConvertWithVisitor instead.
let bridge_param_names: HashSet<String> = config
.trait_bridges
.iter()
.filter_map(|b| b.param_name.clone())
.collect();
// Also collect type aliases used as bridge params (e.g. "VisitorHandle").
let bridge_type_aliases: HashSet<String> = config
.trait_bridges
.iter()
.filter_map(|b| b.type_alias.clone())
.collect();
// Determine if any bridge is configured for the visitor pattern.
// Options-field bridges generate visitor.go regardless of visitor_callbacks.
let visitor_callbacks_enabled = config.ffi.as_ref().is_some_and(|f| f.visitor_callbacks);
let visitor_bridge_cfg = config
.trait_bridges
.iter()
.find(|b| b.bind_via == BridgeBinding::OptionsField);
let has_options_field_bridge = visitor_bridge_cfg.is_some();
let has_visitor_bridge =
has_options_field_bridge || (!config.trait_bridges.is_empty() && visitor_callbacks_enabled);
// Determine if any plugin-style bridges (with register_fn) are configured.
// These are independent of visitor_callbacks and generate trait_bridges.go.
let has_plugin_bridges = config.trait_bridges.iter().any(|b| b.register_fn.is_some());
// Map streaming adapter (owner_type, method_name) → item_type. The callback-based
// FFI export (`<prefix>_<type>_<method>`) cannot be driven from CGO, but the
// companion iterator-handle exports (`_start`, `_next`, `_free`) can — we emit a
// dedicated Go method that drives them and returns a typed channel.
// Adapters missing `owner_type` or `item_type` are skipped (treated as "no Go
// streaming method emitted") rather than producing broken code.
let streaming_methods: HashMap<(String, String), String> = config
.adapters
.iter()
.filter(|a| matches!(a.pattern, AdapterPattern::Streaming))
.filter_map(|a| {
let owner = a.owner_type.clone()?;
let item = a.item_type.clone()?;
Some(((owner, a.name.clone()), item))
})
.collect();
// Collect functions excluded from FFI generation. Go bindings call C symbols directly
// via cgo, so any function excluded from the FFI header must also be excluded here.
let ffi_exclude_functions: HashSet<String> = config
.ffi
.as_ref()
.map(|f| f.exclude_functions.iter().cloned().collect())
.unwrap_or_default();
let mut exclude_types: HashSet<String> = config
.ffi
.as_ref()
.map(|f| f.exclude_types.iter().cloned().collect())
.unwrap_or_default();
if let Some(go_config) = &config.go {
exclude_types.extend(go_config.exclude_types.iter().cloned());
}
// Extend exclude_types with types marked as binding_excluded in the IR.
exclude_types.extend(api.types.iter().filter(|t| t.binding_excluded).map(|t| t.name.clone()));
// Mirror the FFI backend's `contains('<')` filter for declared opaque types: a
// workspace-declared opaque whose `rust_path` carries generic parameters (e.g.
// `axum::http::Request<axum::body::Body>`) cannot be represented in the C ABI,
// so the FFI backend does not emit `_new`/`_free` symbols for it. The Go cgo
// shim references those symbols, so the Go backend must follow the same rule —
// otherwise generated Go code references `C.{prefix}_request_free` which the
// linker cannot resolve.
exclude_types.extend(
config
.opaque_types
.iter()
.filter(|(_, path)| path.contains('<'))
.map(|(name, _)| name.clone()),
);
// Collect value-only types (all fields are primitives). These don't have _to_json
// functions emitted by the FFI backend, so Go codegen must construct them from
// field accessors instead of JSON deserialization.
let value_only_types: HashSet<String> = api
.types
.iter()
.filter(|t| !t.is_opaque && t.fields.iter().all(|f| {
matches!(f.ty, crate::core::ir::TypeRef::Primitive(_) | crate::core::ir::TypeRef::String | crate::core::ir::TypeRef::Char | crate::core::ir::TypeRef::Path)
|| matches!(&f.ty, crate::core::ir::TypeRef::Optional(inner) if matches!(inner.as_ref(), crate::core::ir::TypeRef::Primitive(_) | crate::core::ir::TypeRef::String | crate::core::ir::TypeRef::Char | crate::core::ir::TypeRef::Path))
}))
.map(|t| t.name.clone())
.collect();
let content = format_go_code(&strip_trailing_whitespace(&gen_go_file(
api,
config,
&ffi_prefix,
&pkg_name,
&ffi_lib_name,
&ffi_header,
&ffi_crate_dir,
&output_dir,
&bridge_param_names,
&bridge_type_aliases,
&streaming_methods,
&ffi_exclude_functions,
&exclude_types,
&value_only_types,
visitor_bridge_cfg,
)));
// Build adapter body map (consumed by generators via body substitution)
let _adapter_bodies = crate::adapters::build_adapter_bodies(config, Language::Go)?;
// Compute relative path from Go output dir to project root.
let depth = output_dir.trim_end_matches('/').matches('/').count() + 1;
let to_root = "../".repeat(depth);
let mut files = vec![GeneratedFile {
path: PathBuf::from(format!("{output_dir}binding.go")),
content,
generated_header: true,
}];
// Generate visitor.go when an options-field visitor bridge is configured.
if has_visitor_bridge && let Some(bridge_cfg) = visitor_bridge_cfg {
// Derive vtable_trait_name and options_field from the first options-field bridge,
// which is the only bridge shape that can attach a visitor to an options DTO.
let Some(options_field) = bridge_cfg.resolved_options_field() else {
return Err(crate::core::AlefError::Config(
"Go visitor generation requires trait bridge options_field metadata".to_string(),
)
.into());
};
let vtable_trait_name = bridge_cfg.trait_name.clone();
let options_field = options_field.to_string();
// Look up the visitor trait def in the IR.
let trait_map: HashMap<&str, &crate::core::ir::TypeDef> = api
.types
.iter()
.filter(|t| t.is_trait)
.map(|t| (t.name.as_str(), t))
.collect();
let visitor_trait = trait_map.get(bridge_cfg.trait_name.as_str()).copied();
let visitor_function = find_options_bridge_function(api, bridge_cfg);
let visitor_content = if let (Some(vt), Some(visitor_func)) = (visitor_trait, visitor_function) {
strip_trailing_whitespace(&crate::backends::go::gen_visitor::gen_visitor_file(
api,
&pkg_name,
&ffi_prefix,
&ffi_header,
&ffi_crate_dir,
&to_root,
&vtable_trait_name,
&options_field,
vt,
bridge_cfg,
visitor_func,
))
} else {
eprintln!(
"[alef] gen_visitor_file(go): visitor bridge `{vtable_trait_name}` missing trait or options function in IR, skipping visitor.go"
);
String::new()
};
files.push(GeneratedFile {
path: PathBuf::from(format!("{output_dir}visitor.go")),
content: visitor_content,
generated_header: true,
});
}
// Generate trait_bridges.go for plugin-style bridges (with register_fn).
// Per-call bridges (no register_fn) use visitor.go callbacks via convert() instead.
// This is independent of visitor_callbacks, which only affects per-call bridges.
if has_plugin_bridges {
let trait_bridges_content = strip_trailing_whitespace(&super::trait_bridge::gen_trait_bridges_file(
api,
config,
&pkg_name,
&ffi_prefix,
&ffi_header,
&ffi_crate_dir,
&to_root,
&config.name,
));
if !trait_bridges_content.trim().is_empty() && trait_bridges_content.len() > 100 {
files.push(GeneratedFile {
path: PathBuf::from(format!("{output_dir}trait_bridges.go")),
content: trait_bridges_content,
generated_header: true,
});
}
}
// Generate generate.go with //go:generate directive for FFI library download
let generate_go_content =
crate::backends::go::template_env::render("generate_cgo_flags.go.jinja", minijinja::context! {});
files.push(GeneratedFile {
path: PathBuf::from(format!("{output_dir}generate.go")),
content: generate_go_content,
generated_header: false,
});
// Generate the download tool under cmd/download_ffi/main.go
let crate_version = api.version.to_string();
let repo_url = config.github_repo();
let asset_prefix = config.name.clone();
let download_tool_content = crate::backends::go::template_env::render(
"cmd_download_ffi_main.go.jinja",
minijinja::context! {
ffi_lib_name => &ffi_lib_name,
crate_version => &crate_version,
repo_url => &repo_url,
asset_prefix => &asset_prefix,
},
);
files.push(GeneratedFile {
path: PathBuf::from(format!("{output_dir}cmd/download_ffi/main.go")),
content: download_tool_content,
generated_header: false,
});
// Generate embed_ffi.go with //go:embed directive to ensure header files
// are included when this module is vendored. Go's go mod vendor command only
// includes files that are referenced in the module; this directive tells Go
// to include the include/ directory so that the cgo #include directives work
// in vendored environments.
let embed_ffi_content = crate::backends::go::template_env::render(
"embed_ffi.go.jinja",
minijinja::context! {
pkg_name => &pkg_name,
},
);
files.push(GeneratedFile {
path: PathBuf::from(format!("{output_dir}embed_ffi.go")),
content: embed_ffi_content,
generated_header: false,
});
Ok(files)
}
/// Go bindings are already the public API (single .go file wrapping C FFI).
/// This returns empty since the binding.go file serves as both the FFI layer
/// and the high-level public API for consumers.
fn generate_public_api(
&self,
_api: &ApiSurface,
_config: &ResolvedCrateConfig,
) -> anyhow::Result<Vec<GeneratedFile>> {
// Go's binding.go IS the public API — no additional wrapper needed.
Ok(vec![])
}
fn generate_service_api(
&self,
api: &ApiSurface,
config: &ResolvedCrateConfig,
) -> anyhow::Result<Vec<GeneratedFile>> {
let module_path = config.go_module();
let pkg_name = config
.go
.as_ref()
.and_then(|g| g.package_name.clone())
.unwrap_or_else(|| Self::package_name(&module_path));
let ffi_prefix = config.ffi_prefix();
service_api::generate(api, config, &pkg_name, &ffi_prefix)
}
fn build_config(&self) -> Option<BuildConfig> {
Some(BuildConfig {
tool: "go",
crate_suffix: "",
build_dep: BuildDependency::Ffi,
post_build: vec![],
})
}
}
#[cfg(test)]
mod tests;