Introduce optional serde support for model code generation

This introduces several things to optionally support automatic derive attributes for `serde::{Deserialize, Serialize}` for the generated models:
- introduces a feature flag for `sea-orm-codegen` which optionally includes the serde dependency (can be activated via `cargo build / install --features with-serde`),
- introduces a `WithSerde` enum to indicate if Serialize, Deserialize, or even both should be derived from,
- introduces a feature flag for `sea-orm-cli` which optionally activates the `sea-orm-codegen` feature flag `with-serde` (can also be activated via `cargo build / install --features with-serde`),
- adds an optional cli argument `--with-serde [none: default, serialize, deserialize, both]`
- adds test harness for both compact and expanded generation

Potential TODOs:
- Add conditional compilation for the cli argument `--with-serde`

sea-orm-cli/Cargo.toml

@@ -34,7 +34,7 @@ env_logger = { version = "^0.9" }
 log = { version = "^0.4" }
 
 [features]
-default = [ "runtime-async-std-native-tls" ]
+default = [ "runtime-async-std-native-tls", "with-serde" ]
 runtime-actix-native-tls = [
     "sqlx/runtime-actix-native-tls",
     "sea-schema/runtime-actix-native-tls",
@@ -59,3 +59,6 @@ runtime-tokio-rustls = [
     "sqlx/runtime-tokio-rustls",
     "sea-schema/runtime-tokio-rustls",
 ]
+with-serde = [
+    "sea-orm-codegen/with-serde",
+]

sea-orm-cli/src/cli.rs

@@ -63,6 +63,14 @@ pub fn build_cli() -> App<'static, 'static> {
                         .help("Generate entity file of compact format")
                         .takes_value(false)
                         .conflicts_with("EXPANDED_FORMAT"),
+                )
+                // TODO: How to do conditional compilation for feature: "with-serde"
+                .arg(
+                    Arg::with_name("WITH_SERDE")
+                        .long("with-serde")
+                        .help("Automatically derive serde Serialize / Deserialize traits for the entity (none, serialize, deserialize, both)")
+                        .takes_value(true)
+                        .default_value("none")
                 ),
         )
         .setting(AppSettings::SubcommandRequiredElseHelp);

sea-orm-cli/src/main.rs

@@ -1,8 +1,8 @@
 use clap::ArgMatches;
 use dotenv::dotenv;
 use log::LevelFilter;
-use sea_orm_codegen::{EntityTransformer, OutputFile};
-use std::{error::Error, fmt::Display, fs, io::Write, path::Path, process::Command};
+use sea_orm_codegen::{EntityTransformer, OutputFile, WithSerde};
+use std::{error::Error, fmt::Display, fs, io::Write, path::Path, process::Command, str::FromStr};
 
 mod cli;
 
@@ -26,13 +26,17 @@ async fn run_generate_command(matches: &ArgMatches<'_>) -> Result<(), Box<dyn Er
             let url = args.value_of("DATABASE_URL").unwrap();
             let output_dir = args.value_of("OUTPUT_DIR").unwrap();
             let include_hidden_tables = args.is_present("INCLUDE_HIDDEN_TABLES");
-            let tables = args.values_of("TABLES").unwrap_or_default().collect::<Vec<_>>();
+            let tables = args
+                .values_of("TABLES")
+                .unwrap_or_default()
+                .collect::<Vec<_>>();
             let expanded_format = args.is_present("EXPANDED_FORMAT");
+            let with_serde = args.value_of("WITH_SERDE").unwrap();
             let filter_tables = |table: &str| -> bool {
                 if tables.len() > 0 {
                     return tables.contains(&table);
                 }
-                
+
                 true
             };
             let filter_hidden_tables = |table: &str| -> bool {
@@ -84,7 +88,8 @@ async fn run_generate_command(matches: &ArgMatches<'_>) -> Result<(), Box<dyn Er
                 panic!("This database is not supported ({})", url)
             };
 
-            let output = EntityTransformer::transform(table_stmts)?.generate(expanded_format);
+            let output = EntityTransformer::transform(table_stmts)?
+                .generate(expanded_format, WithSerde::from_str(with_serde).unwrap());
 
             let dir = Path::new(output_dir);
             fs::create_dir_all(dir)?;

sea-orm-codegen/Cargo.toml

@@ -25,6 +25,10 @@ syn = { version = "^1", default-features = false, features = [
 quote = "^1"
 heck = "^0.3"
 proc-macro2 = "^1"
+serde = {version = "^1", optional = true }
 
 [dev-dependencies]
 pretty_assertions = { version = "^0.7" }
+
+[features]
+with-serde = [ "serde" ]