Fix various issues related to enabling go-marshal.

- Add missing build tags to files in the abi package.

- Add the marshal package as a sentry dependency, allowed by deps_test.

- Fix an issue with our top-level go_library BUILD rule, which
  incorrectly shadows the variable containing the input set of source
  files. This caused the expansion for the go_marshal clause to
  silently omit input files.

- Fix formatting when copying build tags to gomarshal-generated files.

- Fix a bug with import statement collision detection in go-marshal.

PiperOrigin-RevId: 295112284

pkg/abi/linux/file_amd64.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build amd64
+
 package linux
 
 // Constants for open(2).

pkg/abi/linux/file_arm64.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build arm64
+
 package linux
 
 // Constants for open(2).

tools/defs.bzl

@@ -117,10 +117,10 @@ def go_library(name, srcs, deps = [], imports = [], stateify = True, marshal = F
         # First, we need to segregate the input files via the special suffixes,
         # and calculate the final output set.
         state_sets = calculate_sets(srcs)
-        for (suffix, srcs) in state_sets.items():
+        for (suffix, src_subset) in state_sets.items():
             go_stateify(
                 name = name + suffix + "_state_autogen_with_imports",
-                srcs = srcs,
+                srcs = src_subset,
                 imports = imports,
                 package = full_pkg,
                 out = name + suffix + "_state_autogen_with_imports.go",
@@ -140,10 +140,10 @@ def go_library(name, srcs, deps = [], imports = [], stateify = True, marshal = F
     if marshal:
         # See above.
         marshal_sets = calculate_sets(srcs)
-        for (suffix, srcs) in marshal_sets.items():
+        for (suffix, src_subset) in marshal_sets.items():
             go_marshal(
                 name = name + suffix + "_abi_autogen",
-                srcs = srcs,
+                srcs = src_subset,
                 debug = False,
                 imports = imports,
                 package = name,
@@ -172,11 +172,11 @@ def go_library(name, srcs, deps = [], imports = [], stateify = True, marshal = F
 
         # See above.
         marshal_sets = calculate_sets(srcs)
-        for (suffix, srcs) in marshal_sets.items():
+        for (suffix, _) in marshal_sets.items():
             _go_test(
                 name = name + suffix + "_abi_autogen_test",
                 srcs = [name + suffix + "_abi_autogen_test.go"],
-                library = ":" + name + suffix,
+                library = ":" + name,
                 deps = marshal_test_deps,
                 **kwargs
             )

tools/go_marshal/gomarshal/generator.go

@@ -123,7 +123,7 @@ func (g *Generator) writeHeader() error {
 	// Emit build tags.
 	if t := tags.Aggregate(g.inputs); len(t) > 0 {
 		b.emit(strings.Join(t.Lines(), "\n"))
-		b.emit("\n")
+		b.emit("\n\n")
 	}
 
 	// Package header.

tools/go_marshal/gomarshal/util.go

@@ -310,7 +310,7 @@ func (i *importStmt) markUsed() {
 }
 
 func (i *importStmt) equivalent(other *importStmt) bool {
-	return i == other
+	return i.name == other.name && i.path == other.path && i.aliased == other.aliased
 }
 
 // importTable represents a collection of importStmts.
@@ -329,7 +329,7 @@ func newImportTable() *importTable {
 // result in a panic.
 func (i *importTable) merge(other *importTable) {
 	for name, im := range other.is {
-		if dup, ok := i.is[name]; ok && dup.equivalent(im) {
+		if dup, ok := i.is[name]; ok && !dup.equivalent(im) {
 			panic(fmt.Sprintf("Found colliding import statements: ours: %+v, other's: %+v", dup, im))
 		}
 
@@ -337,16 +337,27 @@ func (i *importTable) merge(other *importTable) {
 	}
 }
 
+func (i *importTable) addStmt(s *importStmt) *importStmt {
+	if old, ok := i.is[s.name]; ok && !old.equivalent(s) {
+		// A collision should always be between an import inserted by the
+		// go-marshal tool and an import from the original source file (assuming
+		// the original source file was valid). We could theoretically handle
+		// the collision by assigning a local name to our import. However, this
+		// would need to be plumbed throughout the generator. Given that
+		// collisions should be rare, simply panic on collision.
+		panic(fmt.Sprintf("Import collision: old: %s as %v; new: %v as %v", old.path, old.name, s.path, s.name))
+	}
+	i.is[s.name] = s
+	return s
+}
+
 func (i *importTable) add(s string) *importStmt {
 	n := newImport(s)
-	i.is[n.name] = n
-	return n
+	return i.addStmt(n)
 }
 
 func (i *importTable) addFromSpec(spec *ast.ImportSpec, f *token.FileSet) *importStmt {
-	n := newImportFromSpec(spec, f)
-	i.is[n.name] = n
-	return n
+	return i.addStmt(newImportFromSpec(spec, f))
 }
 
 // Marks the import named n as used. If no such import is in the table, returns