From 2c088d03cec73b25ae1a8ffa87a5ea6598904c49 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gabor=20K=C3=B6rber?= <gab@g4b.org>
Date: Thu, 25 Jan 2024 21:59:34 +0100
Subject: [PATCH] code: side-feature: exploring string into solution. will
 probably be moved away

---
 Cargo.lock                     |  9 +++++
 Cargo.toml                     |  1 +
 src/bin/into.rs                | 30 +++++++++++++++
 src/bin/strinto_declarative.rs | 68 ++++++++++++++++++++++++++++++++++
 strinto/.gitignore             |  1 +
 strinto/Cargo.lock             | 47 +++++++++++++++++++++++
 strinto/Cargo.toml             | 14 +++++++
 strinto/src/lib.rs             | 62 +++++++++++++++++++++++++++++++
 8 files changed, 232 insertions(+)
 create mode 100644 src/bin/into.rs
 create mode 100644 src/bin/strinto_declarative.rs
 create mode 100644 strinto/.gitignore
 create mode 100644 strinto/Cargo.lock
 create mode 100644 strinto/Cargo.toml
 create mode 100644 strinto/src/lib.rs

diff --git a/Cargo.lock b/Cargo.lock
index d595b15..cbf1704 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1258,10 +1258,19 @@ dependencies = [
  "regex",
  "rodio",
  "serde",
+ "strinto",
  "tokio",
  "xxhash-rust",
 ]
 
+[[package]]
+name = "strinto"
+version = "0.1.0"
+dependencies = [
+ "quote",
+ "syn 2.0.26",
+]
+
 [[package]]
 name = "symphonia"
 version = "0.5.3"
diff --git a/Cargo.toml b/Cargo.toml
index 53fec25..635ea1b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,3 +21,4 @@ rodio = "0.17.1"
 serde = { version = "1.0.171", features = ["derive"] }
 tokio = { version = "1.29.1", features = ["full"] }
 xxhash-rust = { version = "0.8.6", features = ["xxh3", "const_xxh3"] }
+strinto = { path = "./strinto" }
diff --git a/src/bin/into.rs b/src/bin/into.rs
new file mode 100644
index 0000000..2fbfc04
--- /dev/null
+++ b/src/bin/into.rs
@@ -0,0 +1,30 @@
+#[macro_export]
+macro_rules! into {
+    ($struct:ident { $($field:ident : $value:expr),* $(,)? }) => {
+        $struct {
+            $(
+                $field: $value.into(),
+            )*
+        }
+    };
+}
+
+struct SomeStruct {
+    first_name: String,
+    last_name: String,
+    age: usize,
+}
+
+pub fn main() {
+    let last_name: String = "Last".to_string();
+    let age: usize = 30;
+
+    let x = into!(SomeStruct {
+        first_name: "First",
+        last_name: last_name,
+        age: age,
+    });
+}
+
+// see cargo expand to see how this function changes all struct inits to .into().
+// see also strinto, if you think "Why could it not be done in a macro as condition?"
diff --git a/src/bin/strinto_declarative.rs b/src/bin/strinto_declarative.rs
new file mode 100644
index 0000000..502c6e4
--- /dev/null
+++ b/src/bin/strinto_declarative.rs
@@ -0,0 +1,68 @@
+///
+/// Trying to get around "".into() for String values.
+/// Or "".to_owned().
+/// Or String::from("").
+/// Or "".to_string().
+/// Choose your church.
+///
+/// This is as far as you will get declaratively.
+
+#[macro_export]
+macro_rules! strinto {
+    ($struct:ident { $($field:ident : $value:expr),* $(,)? }) => {
+        $struct {
+            $(
+                $field: $crate::strinto!(@convert $value),
+            )*
+        }
+    };
+
+    (@convert $value:literal) => {
+        match () {
+            _ if stringify!($value).starts_with("\"") => {
+                $value.to_string()
+            },
+            _ => $value.into(), // <-- no getting rid of the into!
+        }
+    };
+}
+
+struct SomeStruct {
+    first_name: String,
+    //last_name: String, // NOPE because of @convert.
+    //age: usize, // reason of .into() in the first place.
+}
+
+pub fn main() {
+    let x = strinto!(SomeStruct {
+        first_name: "First",
+        //last_name: String::from("Last"), // NOPE 2.
+        //age: 1, // NOPE 1. But I went further.
+    });
+}
+
+// while this compiles for only &str "", it is also useless compared to into!
+// the reason is, that you cannot type check in the declarative macros.
+// while yes, you would conditionally run stringify!($value) in the match, but the match expansion
+// will always lead you to type errors if you don't do an .into() in the other arm.
+// also in the end it fails to compile for anything but all members of the struct being Strings.
+
+// the last idea was going with a helper trait, but that will bleed into the runtime code, and yet again only work on pure String structs.
+
+// I guess I have to embrace String::from(), .to_string(), .to_owned(), .into() madness, for something every human reader can deduce in a second,
+// if you would just implicitly convert &str to String if literally written in the code.
+
+// It is kinda amusing, that the other solution, to use new() kind of turns me off, because I cannot be explicit about the parameter name in the call.
+// I would literally love the option to be more explicit in function param names.
+
+// while builder patterns feel a bit bloated for static runtime options, i will probably look into automations for that.
+
+// this is probably the only aesthetic decision in rust I probably will hate forever.
+// It does not make sense, Strings as literals already are special in your code.
+// Because numbers are as well, you dont have to write 123.into() either.
+// I know I probably made some really harsh logical mistakes in my opinion here, and maybe it can be proven, that I am wrong, and I would love to hear that
+// However it kind of feels like an excuse to not simplify assigning declaratively written &str to Strings in the code.
+
+// And it makes sense to be explicit about creating a String Buffer sometimes, but it does not make sense mostly.
+
+// Anyway, I will still try a procedural macro for this, just for fun.
diff --git a/strinto/.gitignore b/strinto/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/strinto/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/strinto/Cargo.lock b/strinto/Cargo.lock
new file mode 100644
index 0000000..7f8aab3
--- /dev/null
+++ b/strinto/Cargo.lock
@@ -0,0 +1,47 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.78"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2422ad645d89c99f8f3e6b88a9fdeca7fabeac836b1002371c4367c8f984aae"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "291ec9ab5efd934aaf503a6466c5d5251535d108ee747472c3977cc5acc868ef"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "strinto"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.48"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0f3531638e407dfc0814761abb7c00a5b54992b849452a0646b7f65c9f770f3f"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
diff --git a/strinto/Cargo.toml b/strinto/Cargo.toml
new file mode 100644
index 0000000..d47f7cc
--- /dev/null
+++ b/strinto/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "strinto"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "2.0", features = ["full"] }
+quote = "1.0"
+
+[dev-dependencies]
+proc-macro2 = "1.0"
diff --git a/strinto/src/lib.rs b/strinto/src/lib.rs
new file mode 100644
index 0000000..b147e4d
--- /dev/null
+++ b/strinto/src/lib.rs
@@ -0,0 +1,62 @@
+extern crate proc_macro;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, Expr, ExprStruct};
+
+/// # literal strings in a struct insantiation are converted .into().
+///
+/// ```rust
+/// use strinto::strinto;
+///    #[derive(Debug)]
+///    struct TestStruct {
+///        name: String,
+///        title: String,
+///        description: String,
+///        age: usize,
+///    }
+///
+///    let descr = "description";
+///
+///    let output = strinto!(TestStruct {
+///        name: "John", // Literal string.
+///        title: String::from("Wicked"),
+///        description: descr.to_string(),
+///        age: 30,
+///    });
+///
+///    let output_string = format!("{:?}", output);
+///    assert_eq!(
+///        output_string,
+///        "TestStruct { name: \"John\", title: \"Wicked\", description: \"description\", age: 30 }"
+///    );
+/// ```
+
+#[proc_macro]
+pub fn strinto(input: TokenStream) -> TokenStream {
+    let expr_struct = parse_macro_input!(input as ExprStruct);
+
+    // Extract struct name and fields
+    let struct_name = &expr_struct.path;
+    let fields = expr_struct.fields.iter().map(|field| {
+        let field_name = field.member.clone();
+        let field_value = &field.expr;
+        // Determine if the field value is a string literal and transform it
+        if let Expr::Lit(expr_lit) = field_value {
+            if let syn::Lit::Str(_) = expr_lit.lit {
+                quote! { #field_name: #field_value.into() }
+            } else {
+                quote! { #field_name: #field_value }
+            }
+        } else {
+            quote! { #field_name: #field_value }
+        }
+    });
+
+    let expanded = quote! {
+        #struct_name {
+            #(#fields,)*
+        }
+    };
+
+    expanded.into()
+}