From 145a9ba8ddc82a3ee693305a8d2eaa955e7ab926 Mon Sep 17 00:00:00 2001
From: Georgy Moshkin <gmoshkin@picodata.io>
Date: Wed, 13 Mar 2024 13:37:37 +0300
Subject: [PATCH] feat: Introspection::set_field_from_yaml
---
pico_proc_macro/src/lib.rs | 274 +++++++++++++++++++++++++++++++++++--
src/config.rs | 1 +
src/introspection.rs | 269 ++++++++++++++++++++++++++++++++++++
src/lib.rs | 1 +
4 files changed, 537 insertions(+), 8 deletions(-)
create mode 100644 src/introspection.rs
diff --git a/pico_proc_macro/src/lib.rs b/pico_proc_macro/src/lib.rs
index ad0ea81af5..2cde5dd5c9 100644
--- a/pico_proc_macro/src/lib.rs
+++ b/pico_proc_macro/src/lib.rs
@@ -1,18 +1,50 @@
use quote::quote;
+macro_rules! unwrap_or_compile_error {
+ ($expr:expr) => {
+ match $expr {
+ Ok(v) => v,
+ Err(e) => {
+ return e.to_compile_error().into();
+ }
+ }
+ };
+}
+
#[allow(clippy::single_match)]
-#[proc_macro_derive(Introspection)]
+#[proc_macro_derive(Introspection, attributes(introspection))]
pub fn derive_introspection(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = syn::parse_macro_input!(input as syn::DeriveInput);
let name = &input.ident;
+ let args = unwrap_or_compile_error!(Args::from_attributes(input.attrs));
+
+ let mut context = Context {
+ args,
+ fields: vec![],
+ };
let mut field_names = vec![];
- match &input.data {
- syn::Data::Struct(ds) => match &ds.fields {
+ match input.data {
+ syn::Data::Struct(ds) => match ds.fields {
syn::Fields::Named(fs) => {
- for field in &fs.named {
- let field_name = field.ident.as_ref().unwrap();
- field_names.push(field_name.to_string());
+ for mut field in fs.named {
+ let attrs = std::mem::take(&mut field.attrs);
+ let attrs = unwrap_or_compile_error!(FieldAttrs::from_attributes(attrs));
+ if attrs.ignore {
+ continue;
+ }
+
+ let name = field_name(&field);
+ field_names.push(name.clone());
+ context.fields.push(FieldInfo {
+ name,
+ ident: field
+ .ident
+ .clone()
+ .expect("Fields::Named has fields with names"),
+ attrs,
+ field,
+ });
}
}
_ => {}
@@ -20,12 +52,238 @@ pub fn derive_introspection(input: proc_macro::TokenStream) -> proc_macro::Token
_ => {}
}
+ let body_for_set_field_from_yaml = generate_body_for_set_field_from_yaml(&context);
+
+ let crate_ = &context.args.crate_;
quote! {
- impl #name {
- pub const FIELD_NAMES: &'static [&'static str] = &[
+ #[automatically_derived]
+ impl #crate_::introspection::Introspection for #name {
+ const FIELD_NAMES: &'static [&'static str] = &[
#( #field_names, )*
];
+
+ fn set_field_from_yaml(&mut self, path: &str, yaml: &str) -> ::std::result::Result<(), #crate_::introspection::IntrospectionError> {
+ use #crate_::introspection::IntrospectionError;
+ #body_for_set_field_from_yaml
+ }
}
}
.into()
}
+
+fn generate_body_for_set_field_from_yaml(context: &Context) -> proc_macro2::TokenStream {
+ let mut set_non_nestable = quote! {};
+ let mut set_nestable = quote! {};
+ let mut error_if_nestable = quote! {};
+ let mut non_nestable_names = vec![];
+ for field in &context.fields {
+ let name = &field.name;
+ let ident = &field.ident;
+ #[allow(non_snake_case)]
+ let Type = &field.field.ty;
+
+ if !field.attrs.nested {
+ non_nestable_names.push(name);
+
+ // Handle assigning to a non-nestable field
+ set_non_nestable.extend(quote! {
+ #name => {
+ match serde_yaml::from_str(yaml) {
+ Ok(v) => {
+ self.#ident = v;
+ return Ok(());
+ }
+ Err(error) => return Err(IntrospectionError::SerdeYaml { field: path.into(), error }),
+ }
+ }
+ });
+ } else {
+ // Handle assigning to a nested sub-field
+ set_nestable.extend(quote! {
+ #name => {
+ return self.#ident.set_field_from_yaml(tail, yaml)
+ .map_err(|e| e.with_prepended_prefix(head));
+ }
+ });
+
+ // Handle if trying to assign to field marked with `#[introspection(nested)]`
+ // This is not currently supported, all of it's subfields must be assigned individually
+ error_if_nestable.extend(quote! {
+ #name => return Err(IntrospectionError::AssignToNested {
+ field: path.into(),
+ example: #Type::FIELD_NAMES.get(0).unwrap_or(&"<actually there's no fields in this struct :(>"),
+ }),
+ })
+ }
+ }
+
+ // Handle if a nested path is specified for non-nestable field
+ let mut error_if_non_nestable = quote! {};
+ if !non_nestable_names.is_empty() {
+ error_if_non_nestable.extend(quote! {
+ #( #non_nestable_names )|* => {
+ return Err(IntrospectionError::NotNestable { field: head.into() })
+ }
+ });
+ }
+
+ // Actual generated body:
+ quote! {
+ match path.split_once('.') {
+ Some((head, tail)) => {
+ let head = head.trim();
+ if head.is_empty() {
+ return Err(IntrospectionError::InvalidPath {
+ expected: "expected a field name before",
+ path: format!(".{tail}"),
+ })
+ }
+ let tail = tail.trim();
+ if !tail.chars().next().map_or(false, char::is_alphabetic) {
+ return Err(IntrospectionError::InvalidPath {
+ expected: "expected a field name after",
+ path: format!("{head}."),
+ })
+ }
+ match head {
+ #error_if_non_nestable
+ #set_nestable
+ _ => {
+ return Err(IntrospectionError::NoSuchField {
+ parent: "".into(),
+ field: head.into(),
+ expected: Self::FIELD_NAMES,
+ });
+ }
+ }
+ }
+ None => {
+ match path {
+ #set_non_nestable
+ #error_if_nestable
+ _ => {
+ return Err(IntrospectionError::NoSuchField {
+ parent: "".into(),
+ field: path.into(),
+ expected: Self::FIELD_NAMES,
+ });
+ }
+ }
+ }
+ }
+ }
+}
+
+struct Context {
+ fields: Vec<FieldInfo>,
+ args: Args,
+}
+
+struct FieldInfo {
+ name: String,
+ ident: syn::Ident,
+ attrs: FieldAttrs,
+ #[allow(unused)]
+ field: syn::Field,
+}
+
+struct Args {
+ crate_: syn::Path,
+}
+
+impl Args {
+ fn from_attributes(attrs: Vec<syn::Attribute>) -> Result<Self, syn::Error> {
+ let mut result = Self {
+ crate_: syn::parse2(quote!(crate)).unwrap(),
+ };
+
+ for attr in attrs {
+ if !attr.path.is_ident("introspection") {
+ continue;
+ }
+
+ let meta: PathKeyValue = attr.parse_args()?;
+ if meta.key.is_ident("crate") {
+ result.crate_ = meta.value;
+ }
+ }
+
+ Ok(result)
+ }
+}
+
+struct FieldAttrs {
+ ignore: bool,
+ nested: bool,
+}
+
+impl FieldAttrs {
+ fn from_attributes(attrs: Vec<syn::Attribute>) -> Result<Self, syn::Error> {
+ let mut result = Self {
+ ignore: false,
+ nested: false,
+ };
+
+ for attr in attrs {
+ if !attr.path.is_ident("introspection") {
+ continue;
+ }
+
+ attr.parse_args_with(|input: syn::parse::ParseStream| {
+ // `input` is a stream of those tokens right there
+ // `#[introspection(foo, bar, ...)]`
+ // ^^^^^^^^^^^^^
+ while !input.is_empty() {
+ let ident = input.parse::<syn::Ident>()?;
+ if ident == "ignore" {
+ result.ignore = true;
+ } else if ident == "nested" {
+ result.nested = true;
+ } else {
+ return Err(syn::Error::new(
+ ident.span(),
+ format!("unknown attribute argument `{ident}`, expected one of `ignore`, `nested`"),
+ ));
+ }
+
+ if !input.is_empty() {
+ input.parse::<syn::Token![,]>()?;
+ }
+ }
+
+ Ok(())
+ })?;
+ }
+
+ Ok(result)
+ }
+}
+
+fn field_name(field: &syn::Field) -> String {
+ // TODO: consider using `quote::format_ident!` instead
+ let mut name = field.ident.as_ref().unwrap().to_string();
+ if name.starts_with("r#") {
+ // Remove 2 leading characters
+ name.remove(0);
+ name.remove(0);
+ }
+ name
+}
+
+#[derive(Debug)]
+struct PathKeyValue {
+ key: syn::Path,
+ #[allow(unused)]
+ eq_token: syn::Token![=],
+ value: syn::Path,
+}
+
+impl syn::parse::Parse for PathKeyValue {
+ fn parse(input: syn::parse::ParseStream) -> Result<Self, syn::Error> {
+ Ok(Self {
+ key: input.parse()?,
+ eq_token: input.parse()?,
+ value: input.parse()?,
+ })
+ }
+}
diff --git a/src/config.rs b/src/config.rs
index d0867f3a18..ada952ab1c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -2,6 +2,7 @@ use crate::address::Address;
use crate::cli::args;
use crate::failure_domain::FailureDomain;
use crate::instance::InstanceId;
+use crate::introspection::Introspection;
use crate::replicaset::ReplicasetId;
use crate::storage;
use crate::tier::Tier;
diff --git a/src/introspection.rs b/src/introspection.rs
new file mode 100644
index 0000000000..379898e9f1
--- /dev/null
+++ b/src/introspection.rs
@@ -0,0 +1,269 @@
+//! This module contains items intended to help with runtime introspection of
+//! rust types. Currently it's mainly used for the [`PicodataConfig`] struct
+//! to simplify the management of configuration parameters and relatetd stuff.
+//!
+//! The main functionality is implemented via the [`Introspection`] trait and
+//! the corresponding derive macro. This trait currently facilitates the ability
+//! to set and get fields of the struct via a path known at runtime. Also it
+//! supports some basic struct field information.
+//!
+//! [`PicodataConfig`]: crate::config::PicodataConfig
+pub use pico_proc_macro::Introspection;
+
+pub trait Introspection {
+ const FIELD_NAMES: &'static [&'static str];
+
+ /// Assign field of `self` described by `path` to value parsed from a given
+ /// `yaml` expression.
+ ///
+ /// When using the `#[derive(Introspection)]` derive macro the implementation
+ /// uses the `serde_yaml` to decode values from yaml. This may change in the
+ /// future.
+ ///
+ /// # Examples:
+ /// ```
+ /// use picodata::introspection::Introspection;
+ ///
+ /// #[derive(Introspection, Default)]
+ /// #[introspection(crate = picodata)]
+ /// struct MyStruct {
+ /// number: i32,
+ /// text: String,
+ /// #[introspection(nested)]
+ /// nested: NestedStruct,
+ /// }
+ ///
+ /// #[derive(Introspection, Default)]
+ /// #[introspection(crate = picodata)]
+ /// struct NestedStruct {
+ /// sub_field: f32,
+ /// }
+ ///
+ /// let mut s = MyStruct::default();
+ /// s.set_field_from_yaml("number", "420").unwrap();
+ /// s.set_field_from_yaml("text", "hello world").unwrap();
+ /// s.set_field_from_yaml("nested.sub_field", "3.14").unwrap();
+ /// ```
+ fn set_field_from_yaml(&mut self, path: &str, yaml: &str) -> Result<(), IntrospectionError>;
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum IntrospectionError {
+ #[error("{}", Self::no_such_field_error_message(.parent, .field, .expected))]
+ NoSuchField {
+ parent: String,
+ field: String,
+ expected: &'static [&'static str],
+ },
+
+ #[error("incorrect value for field '{field}': {error}")]
+ SerdeYaml {
+ field: String,
+ error: serde_yaml::Error,
+ },
+
+ #[error("{expected} '{path}'")]
+ InvalidPath {
+ path: String,
+ expected: &'static str,
+ },
+
+ #[error("field '{field}' has no nested sub-fields")]
+ NotNestable { field: String },
+
+ #[error("field '{field}' cannot be assigned directly, must choose a sub-field (for example '{field}.{example}')")]
+ AssignToNested {
+ field: String,
+ example: &'static str,
+ },
+}
+
+impl IntrospectionError {
+ fn no_such_field_error_message(parent: &str, field: &str, expected: &[&str]) -> String {
+ let mut res = String::with_capacity(128);
+ if !parent.is_empty() {
+ _ = write!(&mut res, "{parent}: ");
+ }
+ use std::fmt::Write;
+ _ = write!(&mut res, "unknown field `{field}`");
+
+ let mut fields = expected.iter();
+ if let Some(first) = fields.next() {
+ _ = write!(&mut res, ", expected one of `{first}`");
+ for next in fields {
+ _ = write!(&mut res, ", `{next}`");
+ }
+ } else {
+ _ = write!(&mut res, ", there are no fields at all");
+ }
+
+ res
+ }
+
+ pub fn prepend_prefix(&mut self, prefix: &str) {
+ match self {
+ Self::NotNestable { field } => {
+ *field = format!("{prefix}.{field}");
+ }
+ Self::InvalidPath { path, .. } => {
+ *path = format!("{prefix}.{path}");
+ }
+ Self::NoSuchField { parent, .. } => {
+ if parent.is_empty() {
+ *parent = prefix.into();
+ } else {
+ *parent = format!("{prefix}.{parent}");
+ }
+ }
+ Self::SerdeYaml { field, .. } => {
+ *field = format!("{prefix}.{field}");
+ }
+ Self::AssignToNested { field, .. } => {
+ *field = format!("{prefix}.{field}");
+ }
+ }
+ }
+
+ #[inline(always)]
+ pub fn with_prepended_prefix(mut self, prefix: &str) -> Self {
+ self.prepend_prefix(prefix);
+ self
+ }
+}
+
+#[cfg(test)]
+mod test {
+ use super::*;
+
+ #[test]
+ fn derive_set_field_from_yaml() {
+ #[derive(Default, Debug, Introspection)]
+ struct S {
+ x: i32,
+ y: f32,
+ s: String,
+ v: Vec<String>,
+ #[introspection(nested)]
+ r#struct: Nested,
+
+ #[introspection(ignore)]
+ ignored: serde_yaml::Value,
+ }
+
+ #[derive(Default, Debug, Introspection)]
+ struct Nested {
+ a: String,
+ b: i64,
+ #[introspection(nested)]
+ empty: Empty,
+ }
+
+ #[derive(Default, Debug, Introspection)]
+ struct Empty {}
+
+ let mut s = S::default();
+
+ //
+ // Check error cases
+ //
+ let e = s.set_field_from_yaml("a", "foo").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "unknown field `a`, expected one of `x`, `y`, `s`, `v`, `struct`"
+ );
+
+ let e = s.set_field_from_yaml(".x", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "expected a field name before '.x'");
+
+ let e = s.set_field_from_yaml("&-*%?!", "foo").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "unknown field `&-*%?!`, expected one of `x`, `y`, `s`, `v`, `struct`"
+ );
+
+ let e = s.set_field_from_yaml("x.foo.bar", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "field 'x' has no nested sub-fields");
+
+ let e = s.set_field_from_yaml("struct", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "field 'struct' cannot be assigned directly, must choose a sub-field (for example 'struct.a')");
+
+ let e = s.set_field_from_yaml("struct.empty", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "field 'struct.empty' cannot be assigned directly, must choose a sub-field (for example 'struct.empty.<actually there's no fields in this struct :(>')");
+
+ let e = s.set_field_from_yaml("struct.foo", "foo").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "struct: unknown field `foo`, expected one of `a`, `b`, `empty`"
+ );
+
+ let e = s.set_field_from_yaml("struct.a.bar", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "field 'struct.a' has no nested sub-fields");
+
+ let e = s.set_field_from_yaml("struct.a..", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "expected a field name after 'struct.a.'");
+
+ let e = s.set_field_from_yaml("x.", "foo").unwrap_err();
+ assert_eq!(e.to_string(), "expected a field name after 'x.'");
+
+ let e = s.set_field_from_yaml("x", "foo").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "incorrect value for field 'x': invalid type: string \"foo\", expected i32"
+ );
+
+ let e = s.set_field_from_yaml("x", "'420'").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "incorrect value for field 'x': invalid type: string \"420\", expected i32"
+ );
+
+ let e = s.set_field_from_yaml("x", "'420'").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "incorrect value for field 'x': invalid type: string \"420\", expected i32"
+ );
+
+ let e = s.set_field_from_yaml("ignored", "foo").unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "unknown field `ignored`, expected one of `x`, `y`, `s`, `v`, `struct`"
+ );
+ assert_eq!(s.ignored, serde_yaml::Value::default());
+
+ let e = s
+ .set_field_from_yaml("struct.empty.foo", "bar")
+ .unwrap_err();
+ assert_eq!(
+ e.to_string(),
+ "struct.empty: unknown field `foo`, there are no fields at all"
+ );
+
+ //
+ // Check success cases
+ //
+ s.set_field_from_yaml("v", "[1, 2, 3]").unwrap();
+ assert_eq!(&s.v, &["1", "2", "3"]);
+ s.set_field_from_yaml("v", "['foo', \"bar\", baz]").unwrap();
+ assert_eq!(&s.v, &["foo", "bar", "baz"]);
+
+ s.set_field_from_yaml("x", "420").unwrap();
+ assert_eq!(s.x, 420);
+
+ s.set_field_from_yaml("y", "13").unwrap();
+ assert_eq!(s.y, 13.0);
+ s.set_field_from_yaml("y", "13.37").unwrap();
+ assert_eq!(s.y, 13.37);
+
+ s.set_field_from_yaml("s", "13.37").unwrap();
+ assert_eq!(s.s, "13.37");
+ s.set_field_from_yaml("s", "foo bar").unwrap();
+ assert_eq!(s.s, "foo bar");
+ s.set_field_from_yaml("s", "'foo bar'").unwrap();
+ assert_eq!(s.s, "foo bar");
+
+ s.set_field_from_yaml(" struct . a ", "aaaa").unwrap();
+ assert_eq!(s.r#struct.a, "aaaa");
+ s.set_field_from_yaml("struct.b", " 0xbbbb ").unwrap();
+ assert_eq!(s.r#struct.b, 0xbbbb);
+ }
+}
diff --git a/src/lib.rs b/src/lib.rs
index ab03f652fa..c97bc38427 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -47,6 +47,7 @@ pub mod governor;
pub mod http_server;
pub mod info;
pub mod instance;
+pub mod introspection;
pub mod ipc;
pub mod kvcell;
pub mod r#loop;
--
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