use codegen, instead of build.rs, to build header file

.cargo/config

@@ -0,0 +1,2 @@
+[alias]
+xtask = "run --package xtask --"

Cargo.lock

@@ -3035,12 +3035,9 @@ name = "taskchampion-lib"
 version = "0.1.0"
 dependencies = [
  "anyhow",
- "cbindgen",
  "chrono",
  "libc",
- "pretty_assertions",
  "taskchampion",
- "uuid",
 ]
 
 [[package]]
@@ -3797,6 +3794,14 @@ dependencies = [
  "time 0.1.43",
 ]
 
+[[package]]
+name = "xtask"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "cbindgen",
+]
+
 [[package]]
 name = "zeroize"
 version = "1.3.0"

Cargo.toml

@@ -6,4 +6,5 @@ members = [
     "sync-server",
     "lib",
     "integration-tests",
+    "xtask",
 ]

README.md

@@ -17,12 +17,18 @@ But, if you just want to get some practice with Rust, we'd be happy to have you.
 
 ## Structure
 
-There are four crates here:
+There are five crates here:
 
  * [taskchampion](./taskchampion) - the core of the tool
  * [taskchampion-cli](./cli) - the command-line binary
  * [taskchampion-sync-server](./sync-server) - the server against which `task sync` operates
- * [replica-server-tests](./replica-server-tests) - integration tests covering both _taskchampion-cli_ and _taskchampion-sync-server_
+ * [taskchampion-lib](./lib) - glue code to use _taskchampion_ from C
+ * [integration-tests](./integration-tests) - integration tests covering _taskchampion-cli_, _taskchampion-sync-server_, and _taskchampion-lib_.
+
+## Code Generation
+
+The _taskchampion_lib_ crate uses a bit of code generation to create the `lib/taskchampion.h` header file.
+To regenerate this file, run `cargo xtask codegen`.
 
 ## Documentation Generation
 

lib/Cargo.toml

@@ -2,7 +2,6 @@
 name = "taskchampion-lib"
 version = "0.1.0"
 edition = "2018"
-build = "build.rs"
 
 [lib]
 name = "taskchampion"
@@ -17,6 +16,3 @@ anyhow = "1.0"
 
 [dev-dependencies]
 pretty_assertions = "1"
-
-[build-dependencies]
-cbindgen = "0.20.0"

lib/build.rs

@@ -1,26 +0,0 @@
-use cbindgen::*;
-
-use std::env;
-
-fn main() {
-    let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
-
-    Builder::new()
-        .with_crate(crate_dir)
-        .with_config(Config {
-            language: Language::C,
-            cpp_compat: true,
-            sys_includes: vec!["stdbool.h".into(), "stdint.h".into(), "time.h".into()],
-            usize_is_size_t: true,
-            no_includes: true,
-            enumeration: EnumConfig {
-                // this appears to still default to true for C
-                enum_class: false,
-                ..Default::default()
-            },
-            ..Default::default()
-        })
-        .generate()
-        .expect("Unable to generate bindings")
-        .write_to_file("taskchampion.h");
-}

xtask/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "xtask"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0"
+cbindgen = "0.20.0"

xtask/src/main.rs

@@ -0,0 +1,47 @@
+//! This executable defines the `cargo xtask` subcommands.
+//!
+//! At the moment it is very simple, but if this grows more subcommands then
+//! it will be sensible to use `clap` or another similar library.
+
+use cbindgen::*;
+use std::env;
+use std::path::PathBuf;
+
+pub fn main() -> anyhow::Result<()> {
+    let arg = env::args().nth(1);
+    match arg.as_ref().map(|arg| arg.as_str()) {
+        Some("codegen") => codegen(),
+        Some(arg) => anyhow::bail!("unknown xtask {}", arg),
+        _ => anyhow::bail!("unknown xtask"),
+    }
+}
+
+/// `cargo xtask codegen`
+///
+/// This uses cbindgen to generate `lib/taskchampion.h`.
+fn codegen() -> anyhow::Result<()> {
+    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
+    let workspace_dir = manifest_dir.parent().unwrap();
+    let lib_crate_dir = workspace_dir.join("lib");
+
+    Builder::new()
+        .with_crate(&lib_crate_dir)
+        .with_config(Config {
+            language: Language::C,
+            cpp_compat: true,
+            sys_includes: vec!["stdbool.h".into(), "stdint.h".into(), "time.h".into()],
+            usize_is_size_t: true,
+            no_includes: true,
+            enumeration: EnumConfig {
+                // this appears to still default to true for C
+                enum_class: false,
+                ..Default::default()
+            },
+            ..Default::default()
+        })
+        .generate()
+        .expect("Unable to generate bindings")
+        .write_to_file(lib_crate_dir.join("taskchampion.h"));
+
+    Ok(())
+}