Support file-level constants

Author: fredemmott

src/CodegenFile.php

@@ -44,6 +44,7 @@ final class CodegenFile {
   private vec<CodegenFunction> $functions = vec[];
   private vec<CodegenType> $beforeTypes = vec[];
   private vec<CodegenType> $afterTypes = vec[];
+  private vec<(string, string, ?string)> $consts = vec[];
   private bool $doClobber = false;
   protected ?CodegenGeneratedFrom $generatedFrom;
   private bool $isSignedFile = true;
@@ -95,6 +96,17 @@ public function addClass(CodegenClassBase $class): this {
     return $this;
   }
 
+  public function addConst<T>(
+    string $name,
+    T $value,
+    ?string $comment = null,
+    IHackBuilderValueRenderer<T> $values_config = HackBuilderValues::export(),
+  ): this {
+    $rendered_value = $values_config->render($this->config, $value);
+    $this->consts[] = tuple($name, $rendered_value, $comment);
+    return $this;
+  }
+
   public function getClasses(): vec<CodegenClassBase> {
     return $this->classes;
   }
@@ -396,6 +408,18 @@ private function getContent(): string {
       $builder->ensureNewLine()->newLine();
       $builder->add($type->render());
     }
+    foreach ($this->consts as list($name, $value, $comment)) {
+      $builder->ensureEmptyLine();
+      if ($comment !== null) {
+        $builder->addDocBlock($comment);
+      }
+      $builder->addWithSuggestedLineBreaksf(
+        "const %s =\t%s;",
+        $name,
+        $value,
+      );
+      $builder->newLine();
+    }
     foreach ($this->functions as $function) {
       $builder->ensureNewLine()->newLine();
       $builder->add($function->render());

test/CodegenFileTest.codegen

@@ -17,6 +17,24 @@ class AllAutogenerated {
   }
 }
 
+!@#$%codegentest:testConstants
+<?hh // strict
+// Codegen Tests
+/**
+ * This file is generated. Do not modify it manually!
+ *
+ * @-generated SignedSource<<3081d5c20598b6bd1aa52a8035ffd207>>
+ */
+namespace Foo\Bar;
+use namespace Herp\Derp;
+
+const string FOO = 'bar';
+
+/**
+ * doc comment
+ */
+const string HERP = 'derp';
+
 !@#$%codegentest:testExecutable
 #!/usr/bin/env hhvm
 <?hh

test/CodegenFileTest.php

@@ -460,4 +460,16 @@ public function testFormattingPartiallyGeneratedFile(): void {
       'bad signed source',
     );
   }
+
+  public function testConstants(): void {
+    $cgf = $this->getCodegenFactory();
+    $code = $cgf
+      ->codegenFile('no_file')
+      ->setNamespace('Foo\\Bar')
+      ->useNamespace('Herp\\Derp')
+      ->addConst('string FOO', 'bar')
+      ->addConst('string HERP', 'derp', 'doc comment')
+      ->render();
+    $this->assertUnchanged($code);
+  }
 }