feat: allow version requirement in cargo-generate.toml

closes #76

Cargo.toml

@@ -35,6 +35,7 @@ toml = "0.5.8"
 thiserror = "1.0.26"
 home = "0.5.3"
 sanitize-filename = "0.3"
+semver = "1.0.4"
 
 [dependencies.openssl]
 version = "0.10.35"

README.md

@@ -355,6 +355,18 @@ exclude = ["*.c"]
 
 The `cargo-generate.toml` file should be placed in the root of the template. If using the `subfolder` feature, the root is the `subfolder` inside the repository, though `cargo-generate` will look for the file in all parent folders until it reaches the repository root.
 
+## Require `cargo-generate` version from template
+
+Using the supported `cargo-generate.toml` file, the template author may setup version requirements towards `cargo-generate`.
+
+```toml
+[template]
+cargo_generate_version = ">0.8.0"
+```
+
+The format for the version requirement is [documented here](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html).
+
+
 ## Cargo gen - alias
 
 `cargo gen` requires an [cargo alias](https://doc.rust-lang.org/cargo/reference/config.html)

src/config.rs

@@ -1,5 +1,6 @@
 use crate::emoji;
 use anyhow::Result;
+use semver::VersionReq;
 use serde::Deserialize;
 use std::path::Path;
 use std::{collections::HashMap, fs};
@@ -20,6 +21,7 @@ pub(crate) struct ConfigValues {
 
 #[derive(Deserialize, Debug, PartialEq)]
 pub(crate) struct TemplateConfig {
+    pub(crate) cargo_generate_version: Option<VersionReq>,
     pub(crate) include: Option<Vec<String>>,
     pub(crate) exclude: Option<Vec<String>>,
 }
@@ -75,6 +77,7 @@ mod tests {
     use super::*;
     use std::fs::File;
     use std::io::Write;
+    use std::str::FromStr;
     use tempfile::tempdir;
     use toml::Value;
 
@@ -87,6 +90,7 @@ mod tests {
         file.write_all(
             r#"
             [template]
+            cargo_generate_version = ">=0.8.0"
             include = ["Cargo.toml"]
             [placeholders]
             test = {a = "a"}
@@ -100,6 +104,7 @@ mod tests {
         assert_eq!(
             config.template,
             Some(TemplateConfig {
+                cargo_generate_version: Some(VersionReq::from_str(">=0.8.0").unwrap()),
                 include: Some(vec!["Cargo.toml".into()]),
                 exclude: None
             })

src/lib.rs

@@ -134,6 +134,7 @@ pub fn generate(mut args: Args) -> Result<()> {
         &locate_template_file(CONFIG_FILE_NAME, &template_base_dir, &args.subfolder).ok(),
     )?;
 
+    check_cargo_generate_version(&template_config)?;
     let template_values = resolve_template_values(&args)?;
 
     println!(
@@ -189,6 +190,34 @@ fn prepare_local_template(args: &Args) -> Result<(TempDir, PathBuf, String), any
     Ok((template_base_dir, template_folder, branch))
 }
 
+fn check_cargo_generate_version(template_config: &Option<Config>) -> Result<(), anyhow::Error> {
+    if let Some(Config {
+        template:
+            Some(config::TemplateConfig {
+                cargo_generate_version: Some(requirement),
+                include: _,
+                exclude: _,
+            }),
+        placeholders: _,
+    }) = template_config
+    {
+        let version = semver::Version::parse(env!("CARGO_PKG_VERSION"))?;
+        if !requirement.matches(&version) {
+            bail!(
+                "{} {} {} {} {}",
+                emoji::ERROR,
+                style("Required cargo-generate version not met. Required:")
+                    .bold()
+                    .red(),
+                style(requirement).bold().yellow(),
+                style(" was:").bold().red(),
+                style(version).bold().yellow(),
+            );
+        }
+    }
+    Ok(())
+}
+
 fn resolve_project_name(args: &Args) -> Result<ProjectName> {
     match args.name {
         Some(ref n) => Ok(ProjectName::new(n)),