feat(extract): model Go native channels as gochan Channel topology

Go's own concurrency primitives were invisible: the Go channel
extractor only classified gorilla/nhooyr WebSocket send/receive, so a
channel-plumbed event pipeline (250 make(chan ...), ~710 send/receive
sites on the measured repo) produced zero Channel nodes and trace_path
stopped dead at every send site.

v1, extraction-only - the existing per-file materializer
(create_channel_edges_for_file and its parallel twin) already builds
Channel nodes and EMITS/LISTENS_ON edges from CBMChannel records:

- send_statement (x <- v) -> EMIT, unary <- -> LISTEN. Both are channel
  operations BY GRAMMAR, so no type inference is needed for precision -
  unlike the WebSocket name heuristics. select comm clauses are covered
  for free (they contain the same node kinds).
- Channel identity: the package-qualified tail identifier
  (module_qn + '.' + field/var name), transport "gochan" - distinct
  from "websocket", whose classifier is untouched. Same-package
  cross-file producer/consumer pairs join on one node.
- Deliberately deferred (documented in #1930): element types on the
  node, go statements (CROSS_ASYNC), and for-range receives - range
  needs the operand's TYPE to know it is a channel, and a name-shape
  guess would be the #1932 anti-pattern.

Also fixes a latent gap this exposed: enclosing_function_qn returned a
BARE name, which never matches any def QN, so every channel edge (the
WebSocket ones included) silently degraded to the file node through
find_channel_source's fallback. It now returns module_qn.name, with
the file-node fallback preserved for shapes it cannot express.

Reproduce-first (RED with extract_channels.c stashed):
extract_go_native_channels (EMIT+LISTEN records, package-qualified
names, unary minus not mistaken for a receive) and
pipeline_go_native_channel_topology (one gochan Channel node,
EMITS from Produce and LISTENS_ON from Drain across files). 643 green
across extraction/pipeline/registry.

Part of #1930

Signed-off-by: Ilya Brykau <ilya.brykau@orca.security>

Author: ilyabrykau-orca

internal/cbm/extract_channels.c

@@ -196,7 +196,13 @@ static const char *enclosing_function_qn(CBMExtractCtx *ctx, TSNode node) {
             if (!ts_node_is_null(name_node)) {
                 char *name = cbm_node_text(ctx->arena, name_node, ctx->source);
                 if (name && name[0]) {
-                    return name;
+                    /* #1930: return a resolvable QN — def QNs are
+                     * module-qualified, so a bare name never matched any node
+                     * and every channel edge silently degraded to the file
+                     * node through find_channel_source's fallback. A miss
+                     * (e.g. a class-nested member) still falls back exactly
+                     * as before. */
+                    return cbm_arena_sprintf(ctx->arena, "%s.%s", ctx->module_qn, name);
                 }
             }
             return NULL;
@@ -625,15 +631,78 @@ static void go_process_call(CBMExtractCtx *ctx, TSNode call) {
     push_channel(ctx, channel_name, "websocket", direction, call);
 }
 
+/* ── #1930: Go native channels ───────────────────────────────────────
+ * `x <- v` and `<-x` are channel operations by GRAMMAR — no type inference is
+ * needed for precision, unlike the WebSocket name-heuristics above. The
+ * channel's v1 identity is its package-qualified tail identifier (the struct
+ * field or variable the operation touches): `s.out <- ev` in package p and
+ * `<-w.out` in another file of p join on `p…out`, which is exactly the
+ * producer/consumer topology trace_path could not cross before. Deliberately
+ * deferred: element types on the node, `go` statements (CROSS_ASYNC), and
+ * `for range ch` receives (range needs the operand's TYPE to know it is a
+ * channel — a name-shape guess here would be the #1932 anti-pattern). */
+static const char *go_chan_expr_name(CBMExtractCtx *ctx, TSNode expr) {
+    const char *kind = ts_node_type(expr);
+    if (strcmp(kind, "parenthesized_expression") == 0 && ts_node_named_child_count(expr) == 1) {
+        return go_chan_expr_name(ctx, ts_node_named_child(expr, 0));
+    }
+    if (strcmp(kind, "identifier") == 0) {
+        return cbm_node_text(ctx->arena, expr, ctx->source);
+    }
+    if (strcmp(kind, "selector_expression") == 0) {
+        TSNode field = ts_node_child_by_field_name(expr, "field", 5);
+        if (!ts_node_is_null(field)) {
+            return cbm_node_text(ctx->arena, field, ctx->source);
+        }
+    }
+    return NULL;
+}
+
+static void go_push_native_channel(CBMExtractCtx *ctx, TSNode site, TSNode chan_expr,
+                                   CBMChannelDirection direction) {
+    const char *tail = go_chan_expr_name(ctx, chan_expr);
+    if (!tail || !tail[0] || strcmp(tail, "_") == 0) {
+        return;
+    }
+    /* Package-qualify so same-named channels in different packages stay
+     * distinct while cross-file uses within one package join. */
+    const char *qualified = cbm_arena_sprintf(ctx->arena, "%s.%s", ctx->module_qn, tail);
+    push_channel(ctx, qualified, "gochan", direction, site);
+}
+
+static void go_process_native_send(CBMExtractCtx *ctx, TSNode node) {
+    TSNode chan_expr = ts_node_child_by_field_name(node, "channel", 7);
+    if (!ts_node_is_null(chan_expr)) {
+        go_push_native_channel(ctx, node, chan_expr, CBM_CHANNEL_EMIT);
+    }
+}
+
+static void go_process_native_receive(CBMExtractCtx *ctx, TSNode node) {
+    TSNode op = ts_node_child_by_field_name(node, "operator", 8);
+    if (ts_node_is_null(op) || ts_node_end_byte(op) - ts_node_start_byte(op) != 2 ||
+        strncmp(ctx->source + ts_node_start_byte(op), "<-", 2) != 0) {
+        return;
+    }
+    TSNode operand = ts_node_child_by_field_name(node, "operand", 7);
+    if (!ts_node_is_null(operand)) {
+        go_push_native_channel(ctx, node, operand, CBM_CHANNEL_LISTEN);
+    }
+}
+
 static void extract_channels_go(CBMExtractCtx *ctx) {
     TSNodeStack stack;
     ts_nstack_init(&stack, ctx->arena, CHAN_STACK_CAP);
     ts_nstack_push(&stack, ctx->arena, ctx->root);
 
     while (stack.count > 0) {
         TSNode node = ts_nstack_pop(&stack);
-        if (strcmp(ts_node_type(node), "call_expression") == 0) {
+        const char *kind = ts_node_type(node);
+        if (strcmp(kind, "call_expression") == 0) {
             go_process_call(ctx, node);
+        } else if (strcmp(kind, "send_statement") == 0) {
+            go_process_native_send(ctx, node);
+        } else if (strcmp(kind, "unary_expression") == 0) {
+            go_process_native_receive(ctx, node);
         }
         uint32_t count = ts_node_child_count(node);
         for (int i = (int)count - SKIP_ONE; i >= 0; i--) {

tests/test_extraction.c

@@ -3015,6 +3015,52 @@ TEST(go_imports) {
     PASS();
 }
 
+TEST(extract_go_native_channels) {
+    /* #1930: `x <- v` and `<-x` are channel operations by grammar — record
+     * them as gochan Channel emits/listens, package-qualified by tail
+     * identifier. Arithmetic unary minus must not be mistaken for a receive. */
+    CBMFileResult *r = extract("package pipe\n"
+                               "\n"
+                               "type Stage struct {\n"
+                               "\tout chan int\n"
+                               "}\n"
+                               "\n"
+                               "func (s *Stage) Push(v int) {\n"
+                               "\ts.out <- v\n"
+                               "}\n"
+                               "\n"
+                               "func (s *Stage) Pull() int {\n"
+                               "\treturn <-s.out\n"
+                               "}\n"
+                               "\n"
+                               "func Neg(v int) int { return -v }\n",
+                               CBM_LANG_GO, "t", "pipe.go");
+    ASSERT_NOT_NULL(r);
+    ASSERT_FALSE(r->has_error);
+    int emits = 0;
+    int listens = 0;
+    for (int i = 0; i < r->channels.count; i++) {
+        const CBMChannel *ch = &r->channels.items[i];
+        ASSERT_NOT_NULL(ch->transport);
+        if (strcmp(ch->transport, "gochan") != 0) {
+            continue;
+        }
+        ASSERT_NOT_NULL(ch->channel_name);
+        size_t len = strlen(ch->channel_name);
+        ASSERT_TRUE(len > 4 && strcmp(ch->channel_name + len - 4, ".out") == 0);
+        ASSERT_NOT_NULL(ch->enclosing_func_qn);
+        if (ch->direction == CBM_CHANNEL_EMIT) {
+            emits++;
+        } else {
+            listens++;
+        }
+    }
+    ASSERT_EQ(emits, 1);
+    ASSERT_EQ(listens, 1);
+    cbm_free_result(r);
+    PASS();
+}
+
 TEST(java_imports) {
     CBMFileResult *r = extract(
         "import java.util.List;\nimport java.util.ArrayList;\nimport static java.lang.Math.PI;\n"
@@ -6699,6 +6745,7 @@ SUITE(extraction) {
     RUN_TEST(python_imports);
     RUN_TEST(js_imports);
     RUN_TEST(go_imports);
+    RUN_TEST(extract_go_native_channels);
     RUN_TEST(java_imports);
     RUN_TEST(rust_imports);
     RUN_TEST(c_imports);

tests/test_pipeline.c

@@ -4688,6 +4688,106 @@ TEST(pipeline_python_receiver_suppresses_weak_method_edge) {
     PASS();
 }
 
+/* #1930: does an edge of this type run from the named function to the named
+ * Channel node? */
+static bool channel_edge_exists(cbm_store_t *s, const char *project, const char *func_name,
+                                const char *channel_name, const char *edge_type) {
+    cbm_node_t *srcs = NULL;
+    cbm_node_t *tgts = NULL;
+    int sc = 0;
+    int tc = 0;
+    cbm_store_find_nodes_by_name(s, project, func_name, &srcs, &sc);
+    cbm_store_find_nodes_by_name(s, project, channel_name, &tgts, &tc);
+    bool found = false;
+    for (int i = 0; i < sc && !found; i++) {
+        cbm_edge_t *edges = NULL;
+        int ec = 0;
+        cbm_store_find_edges_by_source_type(s, srcs[i].id, edge_type, &edges, &ec);
+        for (int j = 0; j < ec && !found; j++) {
+            for (int k = 0; k < tc; k++) {
+                if (edges[j].target_id == tgts[k].id) {
+                    found = true;
+                    break;
+                }
+            }
+        }
+        if (edges) {
+            cbm_store_free_edges(edges, ec);
+        }
+    }
+    if (srcs) {
+        cbm_store_free_nodes(srcs, sc);
+    }
+    if (tgts) {
+        cbm_store_free_nodes(tgts, tc);
+    }
+    return found;
+}
+
+TEST(pipeline_go_native_channel_topology) {
+    /* #1930: the producer/consumer topology of a Go channel pipeline — a send
+     * in one file, a select-receive in another file of the same package —
+     * must materialize as one gochan Channel node with EMITS/LISTENS_ON
+     * edges, so trace_path can cross the channel. RED on main: zero gochan
+     * Channel nodes exist. */
+    char tmp[256];
+    snprintf(tmp, sizeof(tmp), "/tmp/cbm_go_chan_XXXXXX");
+    if (!cbm_mkdtemp(tmp)) {
+        FAIL("tmpdir");
+    }
+    write_temp_file(tmp, "go.mod", "module example.com/fxchan\n\ngo 1.22\n");
+    write_temp_file(tmp, "state/state.go",
+                    "package state\n"
+                    "\n"
+                    "var events = make(chan int, 8)\n"
+                    "\n"
+                    "func Produce(v int) {\n"
+                    "\tevents <- v\n"
+                    "}\n");
+    write_temp_file(tmp, "state/drain.go",
+                    "package state\n"
+                    "\n"
+                    "func Drain() int {\n"
+                    "\tselect {\n"
+                    "\tcase v := <-events:\n"
+                    "\t\treturn v\n"
+                    "\tdefault:\n"
+                    "\t\treturn 0\n"
+                    "\t}\n"
+                    "}\n");
+
+    char db_path[512];
+    snprintf(db_path, sizeof(db_path), "%s/go_chan.db", tmp);
+    cbm_pipeline_t *p = cbm_pipeline_new(tmp, db_path, CBM_MODE_FULL);
+    ASSERT_NOT_NULL(p);
+    ASSERT_EQ(cbm_pipeline_run(p), 0);
+    const char *project = cbm_pipeline_project_name(p);
+
+    cbm_store_t *s = cbm_store_open_path(db_path);
+    ASSERT_NOT_NULL(s);
+
+    /* One package-qualified channel node, transport gochan. */
+    char chan_name[512];
+    snprintf(chan_name, sizeof(chan_name), "%s.state.events", project);
+    cbm_node_t *chans = NULL;
+    int cc = 0;
+    cbm_store_find_nodes_by_name(s, project, chan_name, &chans, &cc);
+    ASSERT_EQ(cc, 1);
+    ASSERT_TRUE(chans[0].label && strcmp(chans[0].label, "Channel") == 0);
+    ASSERT_NOT_NULL(chans[0].properties_json);
+    ASSERT_NOT_NULL(strstr(chans[0].properties_json, "\"transport\":\"gochan\""));
+    cbm_store_free_nodes(chans, cc);
+
+    /* Producer and consumer link the SAME node across files. */
+    ASSERT_TRUE(channel_edge_exists(s, project, "Produce", chan_name, "EMITS"));
+    ASSERT_TRUE(channel_edge_exists(s, project, "Drain", chan_name, "LISTENS_ON"));
+
+    cbm_store_close(s);
+    cbm_pipeline_free(p);
+    th_rmtree(tmp);
+    PASS();
+}
+
 /* Count nodes with the given exact name in the project (e.g. a Route path). */
 static int count_nodes_named(cbm_store_t *s, const char *project, const char *name) {
     cbm_node_t *ns = NULL;
@@ -12805,6 +12905,7 @@ SUITE(pipeline) {
 #endif
     RUN_TEST(pipeline_tsjs_receiver_suppresses_weak_method_edge);
     RUN_TEST(pipeline_python_receiver_suppresses_weak_method_edge);
+    RUN_TEST(pipeline_go_native_channel_topology);
     RUN_TEST(pipeline_tsjs_receiver_parallel_keeps_service_edges);
     RUN_TEST(pipeline_python_receiver_parallel_suppresses_weak_method_edges);
     RUN_TEST(pipeline_parallel_python_cross_only_dunder_gets_synthetic_carrier);