cleanup

apparently, Forgejo provides empty variables for optional
not-specified inputs, for some reason 🤷

.gitignore

@@ -0,0 +1 @@
+target/

Cargo.lock

@@ -0,0 +1,180 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "anode"
+version = "0.1.0"
+dependencies = [
+ "anode-macros",
+ "thiserror",
+]
+
+[[package]]
+name = "anode-build"
+version = "0.1.0"
+dependencies = [
+ "anode-macros-input",
+ "quote",
+ "serde",
+ "syn",
+ "yaml_serde",
+]
+
+[[package]]
+name = "anode-macros"
+version = "0.1.0"
+dependencies = [
+ "anode-macros-input",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "yaml_serde",
+]
+
+[[package]]
+name = "anode-macros-input"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "equivalent"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
+
+[[package]]
+name = "hashbrown"
+version = "0.16.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
+
+[[package]]
+name = "indexmap"
+version = "2.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7714e70437a7dc3ac8eb7e6f8df75fd8eb422675fc7678aff7364301092b1017"
+dependencies = [
+ "equivalent",
+ "hashbrown",
+]
+
+[[package]]
+name = "itoa"
+version = "1.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "92ecc6618181def0457392ccd0ee51198e065e016d1d527a7ac1b6dc7c1f09d2"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.106"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fd00f0bb2e90d81d1044c2b32617f68fcb9fa3bb7640c23e9c748e53fb30934"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "21b2ebcf727b7760c461f091f9f0f539b77b8e87f2fd88131e7f1b433b3cece4"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "ryu"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
+
+[[package]]
+name = "serde"
+version = "1.0.228"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a8e94ea7f378bd32cbbd37198a4a91436180c5bb472411e48b5ec2e2124ae9e"
+dependencies = [
+ "serde_core",
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_core"
+version = "1.0.228"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d385c7d4ca58e59fc732af25c3983b67ac852c1a25000afe1175de458b67ad"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.228"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d540f220d3187173da220f885ab66608367b6574e925011a9353e4badda91d79"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.117"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e665b8803e7b1d2a727f4023456bbbbe74da67099c585258af0ad9c5013b9b99"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "thiserror"
+version = "2.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4288b5bcbc7920c07a1149a35cf9590a2aa808e0bc1eafaade0b80947865fbc4"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "2.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebc4ee7f67670e9b64d05fa4253e753e016c6c95ff35b89b7941d6b856dec1d5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6e4313cd5fcd3dad5cafa179702e2b244f760991f45397d14d4ebf38247da75"
+
+[[package]]
+name = "unsafe-libyaml"
+version = "0.2.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "673aac59facbab8a9007c7f6108d11f63b603f7cabff99fabf650fea5c32b861"
+
+[[package]]
+name = "yaml_serde"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4a7f5270edc6fab0529a772a772b3e505dfd883a8de5cc5b464e35fabe586411"
+dependencies = [
+ "indexmap",
+ "itoa",
+ "ryu",
+ "serde",
+ "unsafe-libyaml",
+]

Cargo.toml

@@ -0,0 +1,25 @@
+[workspace]
+resolver = "3"
+members = [
+    "anode",
+    "anode-macros-input",
+    "anode-build",
+    "anode-macros",
+]
+
+[workspace.dependencies]
+# workspace
+anode = { path = "./anode" }
+anode-macros-input = { path = "./anode-macros-input" }
+anode-macros = { path = "./anode-macros" }
+anode-build = { path = "./anode-build" }
+# crates.io
+syn = { version = "2", default-features = false  }
+quote = { version = "1", default-features = false }
+proc-macro2 = "1.0.102"
+serde = { version = "1", default-features = false }
+yaml_serde = { version = "0.10", default-features = false }
+thiserror = { version = "2", default-features = false }
+
+[workspace.lints.clippy]
+missing_panics_doc = "allow"

README.md

@@ -0,0 +1,16 @@
+Rust toolkit for CI actions
+
+anode -- action without node
+
+# Compile
+
+install
+- libunwind-static
+- xz-static
+
+get C runtime libraries from somewhere (I literally copied them from whatever `gcc` found them in on my system; I think that on actual alpine system they will be found with no problem)
+
+test is compiled with the following command:
+```sh
+RUSTFLAGS="-Lunwind -L/lib/musl/lib -Lcrt -Lxz -llzma" cargo +nightly b -Z build-std -p tests --release --target x86_64-unknown-linux-musl -v
+```

anode-build/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "anode-build"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+anode-macros-input.workspace = true
+serde = {workspace = true, features = ["derive"]}
+syn.workspace = true
+quote.workspace = true
+yaml_serde.workspace = true
+
+[lints]
+workspace = true

anode-build/src/lib.rs

@@ -0,0 +1,85 @@
+// WARN: be aware that both source code file path and output path and hard-coded. they might not work for you; if you have any suggestion for heuristics would determine these paths in a universal way, please let me know
+use syn::{File, punctuated::Punctuated};
+
+use anode_macros_input::pretty_span;
+
+use crate::manifest::ActionManifest;
+
+mod manifest;
+
+pub fn build() {
+    let main_src = std::fs::read_to_string("src/main.rs").unwrap();
+    let main_ast = syn::parse_file(&main_src).unwrap();
+    let input = parse_file(main_ast);
+    let action = anode_macros_input::Action::from_struct(&input);
+    let manifest = ActionManifest::from_action(&action);
+
+    // panic!("{manifest:#?}");
+    std::fs::write(
+        "action.yml",
+        yaml_serde::to_string::<ActionManifest>(&manifest).unwrap(),
+    )
+    .unwrap();
+}
+
+pub fn parse_file(input: File) -> syn::ItemStruct {
+    use syn::{Fields, FieldsNamed, Generics, Item, Path, Token};
+    let structs = input.items.into_iter().filter_map(|item| {
+        if let Item::Struct(struct_) = item {
+            Some(struct_)
+        } else {
+            None
+        }
+    });
+    let with_fields = structs.filter(|str| {
+        if str.generics != Generics::default() {
+            // struct has generics -- not an input
+            println!(
+                "cargo:warn=generics at {} are not allowed in the input struct",
+                pretty_span(&str.generics)
+            );
+            return false;
+        }
+
+        let Fields::Named(FieldsNamed { .. }) = &str.fields else {
+            println!(
+                "cargo:warn=fields at {} must be named for the action input",
+                pretty_span(&str.fields)
+            );
+            return false;
+        };
+        true
+    });
+    let mut with_derive = with_fields
+        .filter(|str| {
+            str.attrs.iter().any(|attr| {
+                if !attr.meta.path().is_ident("derive") {
+                    return false;
+                }
+                let Ok(traits) =
+                    attr.parse_args_with(Punctuated::<Path, Token![,]>::parse_terminated)
+                else {
+                    return false;
+                };
+                traits.iter().any(|tr| {
+                    let input: syn::Path = syn::parse_quote!(Input);
+                    let anode_input: syn::Path = syn::parse_quote!(anode::Input);
+                    tr == &input || tr == &anode_input
+                })
+            })
+        })
+        .collect::<Vec<_>>();
+
+    assert!(
+        !with_derive.is_empty(),
+        "no valid input definition in the main module"
+    );
+
+    assert!(
+        with_derive.len() <= 1,
+        "input module contains multiple valid input definintions: {:#?}",
+        with_derive.iter().map(pretty_span).collect::<Vec<_>>(),
+    );
+
+    with_derive.pop().unwrap()
+}

anode-build/src/manifest.rs

@@ -0,0 +1,142 @@
+use std::collections::BTreeMap;
+
+use quote::ToTokens;
+use syn::{Expr, Ident, parse::Parser};
+
+use anode_macros_input::{Action, ActionInput, pretty_span};
+
+#[derive(Debug, serde::Serialize)]
+pub struct InputManifest {
+    #[serde(skip_serializing_if = "String::is_empty")]
+    pub description: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub r#default: Option<yaml_serde::Value>,
+    pub required: bool,
+}
+
+impl InputManifest {
+    pub fn from_input(input: &ActionInput) -> (&str, InputManifest) {
+        #[expect(
+            clippy::manual_map,
+            reason = "this expression will optionally produce an error in the future"
+        )]
+        let default = if let Some(default) = &input.default {
+            Some(match default {
+                anode_macros_input::ActionInputDefault::Str(s) => {
+                    yaml_serde::Value::String(s.clone().into_string())
+                }
+                anode_macros_input::ActionInputDefault::Expr(expr) => parse_default(expr),
+            })
+        } else {
+            None
+        };
+        (
+            &input.name,
+            InputManifest {
+                description: input.description.clone(),
+                default,
+                required: input.required,
+            },
+        )
+    }
+}
+
+fn parse_default(expr: &Expr) -> yaml_serde::Value {
+    use syn::Lit;
+    use yaml_serde::{Number, Value};
+    let lit = {
+        use syn::parse::Parse;
+        let parser = Lit::parse;
+        #[expect(
+            clippy::match_wild_err_arm,
+            reason = "`_err` can be used for debugging"
+        )]
+        match parser.parse2(expr.to_token_stream()) {
+            Ok(ok) => ok,
+            Err(_err) => panic!(
+                "to allow automatic manifest generation, default value must be a literal. non-literal default for field at {}",
+                pretty_span(expr),
+            ),
+        }
+    };
+    match lit {
+        Lit::Str(lit_str) => Value::String(lit_str.value()),
+        Lit::Bool(lit_bool) => Value::Bool(lit_bool.value()),
+        Lit::Byte(lit_byte) => Value::Number(Number::from(u64::from(lit_byte.value()))),
+        Lit::Char(lit_char) => Value::String(format!("'{}'", lit_char.value())),
+        Lit::Int(lit_int) => {
+            let num = if let Ok(pos_int) = lit_int.base10_parse::<u64>() {
+                Number::from(pos_int)
+            } else if let Ok(neg_int) = lit_int.base10_parse::<i64>() {
+                Number::from(neg_int)
+            } else {
+                panic!("failed to parse int into yaml value: {}", lit_int,);
+            };
+            Value::Number(num)
+        }
+        Lit::Float(lit_float) => {
+            let float = lit_float.base10_parse::<f64>().unwrap();
+            Value::Number(float.into())
+        }
+        Lit::ByteStr(_) => {
+            unimplemented!("bytestr is not a valid yaml value. please use regular str")
+        }
+        Lit::CStr(_) => {
+            unimplemented!("cstr is not a valid yaml literal. please use regular str")
+        }
+        Lit::Verbatim(_) => unimplemented!("uninterpreted literal"),
+        _ => unimplemented!("unknown literal kind"),
+    }
+}
+
+#[derive(Debug, serde::Serialize)]
+pub struct ActionManifest {
+    pub name: String,
+    pub description: String,
+    pub inputs: BTreeMap<String, InputManifest>,
+    pub runs: yaml_serde::Value,
+}
+
+impl ActionManifest {
+    pub fn from_action(action: &Action) -> Self {
+        let name = action
+            .name_override
+            .clone()
+            .unwrap_or_else(|| action.name.to_string());
+        // collect both input manifests AND their idents, to provide informative error messages
+        let mut inputs = BTreeMap::<&str, (InputManifest, Ident)>::new();
+        for input in &action.inputs {
+            use std::collections::btree_map::Entry;
+            let (name, mani) = InputManifest::from_input(input);
+            match inputs.entry(name) {
+                Entry::Vacant(vacant_entry) => {
+                    vacant_entry.insert((mani, input.ident.clone()));
+                }
+                Entry::Occupied(occupied_entry) => {
+                    // input mapping to the same name already exists
+                    let (_, prev_ident) = occupied_entry.get();
+                    panic!(
+                        "Fields at {} and {} map to the same name ({})",
+                        pretty_span(&input.ident),
+                        pretty_span(prev_ident),
+                        name,
+                    );
+                }
+            }
+        }
+        ActionManifest {
+            name,
+            description: action.description.clone(),
+            // strip the idents out
+            inputs: inputs
+                .into_iter()
+                .map(|(k, (v, _))| (k.to_owned(), v))
+                .collect(),
+            runs: runs(),
+        }
+    }
+}
+
+fn runs() -> yaml_serde::Value {
+    yaml_serde::from_str::<yaml_serde::Value>(include_str!("runs.yml")).unwrap()
+}

anode-build/src/runs.yml

@@ -0,0 +1,4 @@
+using: composite
+steps:
+  - run: ${{ forgejo.action_path }}/main
+    shell: bash

anode-macros-input/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "anode-macros-input"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+proc-macro2 = { workspace = true, features = [ "span-locations" ] }
+syn = { workspace = true, features = [ "parsing", "printing", "full", "extra-traits", "clone-impls"] }
+quote.workspace = true
+
+[lints]
+workspace = true

anode-macros-input/src/lib.rs

@@ -0,0 +1,246 @@
+use syn::{
+    AngleBracketedGenericArguments, Attribute, Expr, ExprLit, Field, GenericArgument, Ident, Lit,
+    LitStr, Meta, MetaNameValue, Path, PathArguments, PathSegment, Type, TypePath,
+    spanned::Spanned,
+};
+
+pub enum ActionInputDefault {
+    Str(Box<str>),
+    Expr(Box<Expr>),
+}
+
+pub struct ActionInput {
+    pub ident: syn::Ident,
+    pub name: String,
+    pub description: String,
+    pub r#default: Option<ActionInputDefault>,
+    pub required: bool,
+    pub ty: Type,
+    pub parser: Option<Path>,
+}
+
+pub struct Action {
+    pub name: Ident,
+    pub name_override: Option<String>,
+    pub description: String,
+    pub inputs: Vec<ActionInput>,
+}
+
+impl Action {
+    pub fn from_struct(
+        syn::ItemStruct {
+            attrs,
+            ident,
+            fields,
+            ..
+        }: &syn::ItemStruct,
+    ) -> Self {
+        let mut name_override = Option::<String>::None;
+        let description = parse_desc(attrs);
+        for attr in attrs {
+            if attr.path().is_ident("name")
+                && let Meta::NameValue(MetaNameValue {
+                    value:
+                        Expr::Lit(ExprLit {
+                            lit: Lit::Str(rename),
+                            ..
+                        }),
+                    ..
+                }) = &attr.meta
+            {
+                let token = rename.token();
+                let mut literal = token.to_string();
+                literal.pop().unwrap();
+                literal.remove(0);
+                name_override = Some(literal);
+            }
+        }
+
+        let mut inputs = Vec::new();
+        for field in fields {
+            inputs.push(parse_input(field));
+        }
+        Action {
+            name: ident.clone(),
+            name_override,
+            description,
+            inputs,
+        }
+    }
+}
+
+pub fn pretty_span<T: Spanned>(t: &T) -> String {
+    let span2 = t.span();
+    let start = span2.start();
+    let end = span2.end();
+    let at = if start.line == end.line {
+        format_args!("line {}:{}-{}", start.line, start.column, end.column)
+    } else {
+        format_args!("lines {}-{}", start.line, end.line)
+    };
+    format!("at {at} in main.rs")
+}
+
+fn parse_input(field: &Field) -> ActionInput {
+    let Field {
+        attrs, ident, ty, ..
+    } = field;
+    let name = to_kebab(&ident.as_ref().unwrap().to_string());
+    let description = parse_desc(attrs);
+    let required = if let Type::Path(TypePath {
+        qself: None,
+        path: Path { segments, .. },
+    }) = ty
+        && let Some(PathSegment { ident, .. }) = segments.first()
+        && ident == "Option"
+    {
+        false
+    } else {
+        true
+    };
+
+    // first, assign the default parser, if it can be inferred from the type
+    let mut parser = infer_parser(ty);
+
+    let mut default = Option::<ActionInputDefault>::None;
+
+    for attr in attrs {
+        if attr.path().is_ident("default") {
+            default = Some(ActionInputDefault::Expr(Box::new(
+                attr.parse_args::<Expr>().unwrap(),
+            )));
+        }
+
+        if attr.path().is_ident("default_str") {
+            default = Some(ActionInputDefault::Str(
+                attr.parse_args::<LitStr>()
+                    .unwrap()
+                    .value()
+                    .into_boxed_str(),
+            ));
+        }
+
+        if attr.path().is_ident("parser") {
+            parser = Some(attr.parse_args::<Path>().unwrap());
+        }
+    }
+
+    ActionInput {
+        description,
+        default,
+        required,
+        parser,
+        ident: field.ident.clone().expect("field must have an ident"),
+        name,
+        ty: ty.clone(),
+    }
+}
+
+fn parse_desc(attrs: &[Attribute]) -> String {
+    let mut description = String::new();
+    for attr in attrs {
+        if attr.path().is_ident("doc")
+            && let Meta::NameValue(MetaNameValue {
+                value:
+                    Expr::Lit(ExprLit {
+                        lit: Lit::Str(doc), ..
+                    }),
+                ..
+            }) = &attr.meta
+        {
+            let token = doc.token();
+            let mut literal = token.to_string();
+            literal.pop().unwrap();
+            literal.remove(0);
+            if literal.starts_with(' ') {
+                literal.remove(0);
+            }
+            if !description.is_empty() {
+                description.push('\n');
+            }
+            description.push_str(&literal);
+        }
+    }
+    description
+}
+
+pub fn to_kebab(name: &str) -> String {
+    let mut name = name.trim_start_matches(['-', '_']).replace('_', "-");
+    let mut name = name.as_mut_str();
+    assert!(!name.is_empty()); // TODO that's an invalid ident error, use proper signaling
+    let mut res = String::new();
+    while !name.is_empty() {
+        let next_upper = name
+            .find(|ch: char| ch.is_ascii_uppercase())
+            .unwrap_or(name.len());
+        let (this, rest) = name.split_at_mut(next_upper);
+        name = rest;
+        if !res.is_empty() {
+            res.push('-');
+        }
+        res.push_str(this);
+        if let Some((ind, _)) = name.char_indices().nth(1) {
+            name[..ind].make_ascii_lowercase();
+        } else {
+            name.make_ascii_lowercase();
+        }
+    }
+    res
+}
+
+macro_rules! mch {
+    ($p:pat = $e:expr) => {
+        let $p = $e else {
+            return None;
+        };
+    };
+}
+
+fn infer_parser(ty: &Type) -> Option<Path> {
+    // ensure that type is a single-length path at the top (that covers both well-known types and any `Option<T>`)
+    mch!(
+        Type::Path(TypePath {
+            qself: None,
+            path: Path { segments, .. },
+        }) = ty
+    );
+    if segments.len() != 1 {
+        return None;
+    }
+    let PathSegment { ident, arguments } = segments.first()?;
+
+    if let PathArguments::None = arguments {
+        // no arguments and simple ident -- use well-known parser
+        return Some(syn::parse_quote!(::anode::__default_parser::#ident));
+    }
+
+    // at this point, if the parser can be inferred, type must be an option
+    if ident != "Option" {
+        return None;
+    }
+    mch!(
+        PathArguments::AngleBracketed(AngleBracketedGenericArguments {
+            args: arguments,
+            ..
+        }) = arguments
+    );
+    if arguments.len() != 1 {
+        // real `Option` has only 1 argument
+        return None;
+    }
+    mch!(
+        Some(GenericArgument::Type(Type::Path(TypePath {
+            qself: None,
+            path: Path { segments, .. },
+        }))) = arguments.first()
+    );
+    if segments.len() != 1 {
+        // simple type must be just an ident
+        return None;
+    }
+
+    let PathSegment { ident, .. } = segments.first()?;
+
+    // well-known parser for the inner type
+    Some(syn::parse_quote!(::anode::__default_parser::#ident))
+}

anode-macros/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "anode-macros"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+anode-macros-input = { workspace = true }
+yaml_serde.workspace = true
+proc-macro2.workspace = true
+syn = { workspace = true, features = [ "parsing", "proc-macro" ] }
+quote.workspace = true
+
+[lints]
+workspace = true

anode-macros/src/lib.rs

@@ -0,0 +1,134 @@
+use anode_macros_input::{Action, ActionInput, ActionInputDefault};
+use proc_macro::TokenStream as TStream1;
+use proc_macro2::Span;
+use quote::{ToTokens, format_ident};
+use syn::{
+    ExprStruct, FieldValue, Ident, ItemFn, LitStr, Member, Stmt, Token,
+    punctuated::Punctuated,
+    token::{Brace, Colon},
+};
+
+#[proc_macro_derive(Input, attributes(name, default, default_str, parser))]
+pub fn input(item: TStream1) -> TStream1 {
+    let input = syn::parse_macro_input!(item as syn::ItemStruct);
+    let ident = &input.ident;
+    let action = Action::from_struct(&input);
+    let try_get_impl = try_get(&action);
+
+    let get_impl: syn::ItemFn = syn::parse_quote! {
+        fn get() -> Self {
+            Self::try_get().expect("Failed to parse the input")
+        }
+    };
+
+    let impl_block: syn::ItemImpl = syn::parse_quote! {
+        impl #ident {
+            #try_get_impl
+            #get_impl
+        }
+    };
+    impl_block.into_token_stream().into()
+}
+
+fn try_get(action: &Action) -> ItemFn {
+    let mut body = Vec::<Stmt>::new();
+    let errors = format_ident!("errors");
+    body.push(
+        syn::parse_quote! { let mut #errors = ::std::vec::Vec::<(&'static str, ::anode::InputErrorMessage)>::new(); },
+    );
+
+    let mut idents = Vec::<(Ident, Ident)>::new();
+    let mut required_idents = Vec::<Ident>::new();
+    for (
+        ActionInput {
+            name,
+            parser,
+            required,
+            r#default,
+            ident: struct_ident,
+            ..
+        },
+        i,
+    ) in action.inputs.iter().zip(0..)
+    {
+        let input_ident = format_ident!("f{i}");
+        body.push(syn::parse_quote! { let mut #input_ident: Option<_> = None; });
+
+        let input_lit = LitStr::new(name, proc_macro2::Span::call_site());
+        let input_envvar = LitStr::new(
+            &format!("INPUT_{}", name.to_uppercase()),
+            proc_macro2::Span::call_site(),
+        );
+        let mut envvar: syn::Expr = syn::parse_quote!( ::std::env::var_os(#input_envvar) );
+        if let Some(ActionInputDefault::Str(default_str)) = default {
+            // has default str value -- use it as a fallback
+            let def = LitStr::new(&default_str, Span::call_site());
+            envvar = syn::parse_quote!( #envvar.or_else(|| Some(::std::ffi::OsString::from(String::from(#def)))) );
+        }
+        let mut parse_input: syn::ExprIf = syn::parse_quote! {
+            if let Some(envvar) = #envvar && !envvar.is_empty() {
+                match #parser(envvar) {
+                    Ok(ok) => #input_ident = Some(ok),
+                    Err(error) => #errors.push((#input_lit, ::anode::InputErrorMessage::Parsing(::std::boxed::Box::new(error)))),
+                }
+            }
+        };
+        // else branch, if this input is required
+        if *required {
+            let else_branch = if let Some(ActionInputDefault::Expr(default_expr)) = default {
+                // has a default expression value -- assign it instead
+                syn::parse_quote! {{
+                    #input_ident = Some(#default_expr);
+                }}
+            } else {
+                // no default - error
+                syn::parse_quote! {{
+                    #errors.push((#input_lit, ::anode::InputErrorMessage::NotPresent));
+                }}
+            };
+
+            parse_input.else_branch = Some((<Token![else]>::default(), Box::new(else_branch)));
+        }
+        body.push(syn::parse_quote! (#parse_input));
+        idents.push((input_ident.clone(), struct_ident.clone()));
+        if *required {
+            required_idents.push(input_ident);
+        }
+    }
+
+    // assert there are no errors, and all required fields are present
+    body.push(syn::parse_quote! {
+        let (#(Some(#required_idents)),*, &[]) = (#(#required_idents),*, &*#errors) else {
+            return Err(::anode::InputError(#errors.into_boxed_slice()));
+        };
+    });
+
+    // return the struct
+    let mut fields = Punctuated::new();
+    for (val, member) in idents {
+        fields.push(FieldValue {
+            attrs: Vec::new(),
+            member: Member::Named(member),
+            colon_token: Some(Colon::default()),
+            expr: syn::parse_quote!(#val),
+        });
+    }
+    let str = ExprStruct {
+        attrs: Vec::new(),
+        qself: None,
+        path: syn::parse_quote!(Self),
+        brace_token: Brace::default(),
+        fields,
+        dot2_token: None,
+        rest: None,
+    };
+    body.push(syn::parse_quote! {
+        return Ok(#str);
+    });
+
+    syn::parse_quote! {
+        fn try_get() -> Result<Self, ::anode::InputError> {
+            #(#body)*
+        }
+    }
+}

anode/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "anode"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+anode-macros.workspace = true
+thiserror.workspace = true

anode/src/lib.rs

@@ -0,0 +1,118 @@
+pub use anode_macros::Input;
+
+#[doc(hidden)]
+pub mod __default_parser {
+    #![allow(non_snake_case)]
+
+    use std::{
+        ffi::OsString,
+        os::unix::ffi::{OsStrExt, OsStringExt},
+        path::PathBuf,
+    };
+
+    #[derive(Debug, thiserror::Error)]
+    pub enum InputIntError {
+        #[error(transparent)]
+        Uft8(#[from] core::str::Utf8Error),
+        #[error(transparent)]
+        Parse(#[from] core::num::ParseIntError),
+    }
+
+    macro_rules! int {
+        ($t:ident) => {
+            pub fn $t(input: OsString) -> Result<$t, InputIntError> {
+                let str = core::str::from_utf8(input.as_bytes())?;
+                Ok(str.parse::<$t>()?)
+            }
+        };
+    }
+
+    int!(i8);
+    int!(u8);
+    int!(i16);
+    int!(u16);
+    int!(i32);
+    int!(u32);
+    int!(i64);
+    int!(u64);
+    int!(i128);
+    int!(u128);
+
+    #[derive(Debug, thiserror::Error)]
+    pub enum InputFloatError {
+        #[error(transparent)]
+        Uft8(#[from] core::str::Utf8Error),
+        #[error(transparent)]
+        Parse(#[from] core::num::ParseFloatError),
+    }
+
+    macro_rules! flt {
+        ($t:ident) => {
+            pub fn $t(input: OsString) -> Result<$t, InputFloatError> {
+                let str = core::str::from_utf8(input.as_bytes())?;
+                Ok(str.parse::<$t>()?)
+            }
+        };
+    }
+
+    flt!(f32);
+    flt!(f64);
+
+    pub fn String(input: OsString) -> Result<String, std::string::FromUtf8Error> {
+        let bytes = input.into_vec();
+        String::from_utf8(bytes)
+    }
+
+    pub fn OsString(input: OsString) -> Result<OsString, core::convert::Infallible> {
+        Ok(input)
+    }
+
+    pub fn PathBuf(input: OsString) -> Result<PathBuf, core::convert::Infallible> {
+        Ok(input.into())
+    }
+
+    #[derive(Debug, thiserror::Error)]
+    #[error("Unknown boolean value: {}", _0.display())]
+    pub struct UnknownBoolean(OsString);
+
+    pub fn bool(input: OsString) -> Result<bool, UnknownBoolean> {
+        const VALID_TRUE: &[&[u8]] = &[b"TRUE", b"True", b"true", b"1"];
+        const VALID_FALSE: &[&[u8]] = &[b"FALSE", b"False", b"false", b"0"];
+        if VALID_TRUE.contains(&input.as_bytes()) {
+            return Ok(true);
+        }
+
+        if VALID_FALSE.contains(&input.as_bytes()) {
+            return Ok(false);
+        }
+
+        Err(UnknownBoolean(input))
+    }
+}
+
+pub mod parse {
+    use std::{ffi::OsString, os::unix::ffi::OsStrExt, str::FromStr};
+
+    #[derive(Debug, thiserror::Error)]
+    pub enum InputFromStrError<T: FromStr> {
+        #[error(transparent)]
+        Uft8(#[from] core::str::Utf8Error),
+        #[error(transparent)]
+        Parse(T::Err),
+    }
+
+    pub fn from_str<T: FromStr>(input: OsString) -> Result<T, InputFromStrError<T>> {
+        let str = core::str::from_utf8(input.as_bytes())?;
+        str.parse::<T>().map_err(InputFromStrError::Parse)
+    }
+}
+
+#[derive(Debug)]
+pub struct InputError(#[doc(hidden)] pub Box<[(&'static str, InputErrorMessage)]>);
+
+#[derive(Debug)]
+#[doc(hidden)]
+pub enum InputErrorMessage {
+    NotPresent,
+    Parsing(Box<dyn core::error::Error>),
+}