docs(codegen): add #![warn(missing_docs)] to oxc_codegen (#6711)

Part of https://github.com/oxc-project/backlog/issues/130

crates/oxc_codegen/src/context.rs

@@ -1,3 +1,4 @@
+#![allow(missing_docs)] // FIXME
 use bitflags::bitflags;
 
 bitflags! {

crates/oxc_codegen/src/gen.rs

@@ -15,17 +15,23 @@ use crate::{
     Codegen, Context, Operator,
 };
 
+/// Generate source code for an AST node.
 pub trait Gen: GetSpan {
+    /// Generate code for an AST node.
     fn gen(&self, p: &mut Codegen, ctx: Context);
 
+    /// Generate code for an AST node. Alias for `gen`.
     fn print(&self, p: &mut Codegen, ctx: Context) {
         self.gen(p, ctx);
     }
 }
 
+/// Generate source code for an expression.
 pub trait GenExpr: GetSpan {
+    /// Generate code for an expression, respecting operator precedence.
     fn gen_expr(&self, p: &mut Codegen, precedence: Precedence, ctx: Context);
 
+    /// Generate code for an expression, respecting operator precedence. Alias for `gen_expr`.
     fn print_expr(&self, p: &mut Codegen, precedence: Precedence, ctx: Context) {
         self.gen_expr(p, precedence, ctx);
     }

crates/oxc_codegen/src/lib.rs

@@ -2,6 +2,7 @@
 //!
 //! Code adapted from
 //! * [esbuild](https://github.com/evanw/esbuild/blob/main/internal/js_printer/js_printer.go)
+#![warn(missing_docs)]
 
 mod binary_expr_visitor;
 mod code_buffer;
@@ -36,6 +37,7 @@ pub use crate::{
 /// Code generator without whitespace removal.
 pub type CodeGenerator<'a> = Codegen<'a>;
 
+/// Options for [`Codegen`].
 #[derive(Debug, Clone)]
 pub struct CodegenOptions {
     /// Use single quotes instead of double quotes.
@@ -60,6 +62,11 @@ pub struct CodegenOptions {
     /// Default is `false`.
     pub annotation_comments: bool,
 
+    /// Override the source map path. This affects the `sourceMappingURL`
+    /// comment at the end of the generated code.
+    ///
+    /// By default, the source map path is the same as the input source code
+    /// (with a `.map` extension).
     pub source_map_path: Option<PathBuf>,
 }
 
@@ -92,6 +99,24 @@ pub struct CodegenReturn {
     pub map: Option<oxc_sourcemap::SourceMap>,
 }
 
+/// A code generator for printing JavaScript and TypeScript code.
+///
+/// ## Example
+/// ```rust
+/// use oxc_codegen::{Codegen, CodegenOptions};
+/// use oxc_ast::ast::Program;
+/// use oxc_parser::Parser;
+/// use oxc_allocator::Allocator;
+/// use oxc_span::SourceType;
+///
+/// let allocator = Allocator::default();
+/// let source = "const a = 1 + 2;";
+/// let parsed = Parser::new(&allocator, source, SourceType::mjs()).parse();
+/// assert!(parsed.errors.is_empty());
+///
+/// let js = Codegen::new().build(&parsed.program);
+/// assert_eq!(js.code, "const a = 1 + 2;\n");
+/// ```
 pub struct Codegen<'a> {
     pub(crate) options: CodegenOptions,
 
@@ -164,6 +189,9 @@ impl<'a> From<Codegen<'a>> for Cow<'a, str> {
 
 // Public APIs
 impl<'a> Codegen<'a> {
+    /// Create a new code generator.
+    ///
+    /// This is equivalent to [`Codegen::default`].
     #[must_use]
     pub fn new() -> Self {
         Self {
@@ -189,6 +217,7 @@ impl<'a> Codegen<'a> {
         }
     }
 
+    /// Pass options to the code generator.
     #[must_use]
     pub fn with_options(mut self, options: CodegenOptions) -> Self {
         self.quote = if options.single_quote { b'\'' } else { b'"' };
@@ -196,12 +225,15 @@ impl<'a> Codegen<'a> {
         self
     }
 
+    /// Set the mangler for mangling identifiers.
     #[must_use]
     pub fn with_mangler(mut self, mangler: Option<Mangler>) -> Self {
         self.mangler = mangler;
         self
     }
 
+    /// Print a [`Program`] into a string of source code. A source map will be
+    /// generated if [`CodegenOptions::source_map_path`] is set.
     #[must_use]
     pub fn build(mut self, program: &Program<'a>) -> CodegenReturn {
         self.quote = if self.options.single_quote { b'\'' } else { b'"' };
@@ -220,6 +252,14 @@ impl<'a> Codegen<'a> {
         CodegenReturn { code, map }
     }
 
+    /// Turn what's been built so far into a string. Like [`build`],
+    /// this fininishes a print and returns the generated source code. Unlike
+    /// [`build`], no source map is generated.
+    ///
+    /// This is more useful for cases that progressively build code using [`print_expression`].
+    ///
+    /// [`build`]: Codegen::build
+    /// [`print_expression`]: Codegen::print_expression
     #[must_use]
     pub fn into_source_text(self) -> String {
         self.code.into_string()
@@ -240,6 +280,8 @@ impl<'a> Codegen<'a> {
         self.code.print_str(s);
     }
 
+    /// Print a single [`Expression`], adding it to the code generator's
+    /// internal buffer. Unlike [`Codegen::build`], this does not consume `self`.
     #[inline]
     pub fn print_expression(&mut self, expr: &Expression<'_>) {
         expr.print_expr(self, Precedence::Lowest, Context::empty());