Make it easier to test scenario modifiers by specifying them on the CLI

abstutil/src/serde.rs

@@ -10,6 +10,10 @@ pub fn to_json<T: Serialize>(obj: &T) -> String {
     serde_json::to_string_pretty(obj).unwrap()
 }
 
+pub fn to_json_terse<T: Serialize>(obj: &T) -> String {
+    serde_json::to_string(obj).unwrap()
+}
+
 pub fn from_json<T: DeserializeOwned>(raw: &Vec<u8>) -> Result<T, Box<dyn Error>> {
     serde_json::from_slice(raw).map_err(|x| x.into())
 }

book/src/trafficsim/gridlock.md

@@ -98,7 +98,8 @@ particular order:
 - Use the `--disable_block_the_box` flag to workaround short roads.
 - If you notice problems forming from cars stacking up behind slower cyclists,
   there's no over-taking implemented yet. Use the scenario modifiers to convert
-  all biking trip to driving.
+  all biking trip to driving:
+  `--scenario_modifiers='[{"ChangeMode":{"to_mode":"Drive","pct_ppl":100,"departure_filter":[0.0,86400.0],"from_modes":["Bike"]}}]'`
 - If all else fails, use the scenario modifiers to bluntly cancel some
   percentage of all trips.
 

game/src/lib.rs

@@ -3,7 +3,7 @@ extern crate log;
 
 use abstutil::{CmdArgs, Timer};
 use geom::Duration;
-use sim::SimFlags;
+use sim::{ScenarioModifier, SimFlags};
 
 use crate::app::Flags;
 
@@ -113,10 +113,15 @@ pub fn main() {
         let map_name = parts[parts.len() - 2].to_string();
         let scenario = abstutil::basename(parts[parts.len() - 1]);
         flags.sim_flags.load = abstutil::path_map(&map_name);
+
+        let modifiers: Vec<ScenarioModifier> = args
+            .optional_parse("--scenario_modifiers", |s| {
+                abstutil::from_json(&s.to_string().into_bytes())
+            })
+            .unwrap_or_else(Vec::new);
+
         mode = Some(sandbox::GameplayMode::PlayScenario(
-            map_name,
-            scenario,
-            Vec::new(),
+            map_name, scenario, modifiers,
         ));
     }
     let start_with_edits = args.optional("--edits");

game/src/sandbox/gameplay/play_scenario.rs

@@ -233,6 +233,12 @@ impl State for EditScenarioModifiers {
                     return Transition::Pop;
                 }
                 "Apply" => {
+                    info!("To apply these modifiers in the future:");
+                    info!(
+                        "--scenario_modifiers='{}'",
+                        abstutil::to_json_terse(&self.modifiers)
+                    );
+
                     return Transition::Multi(vec![
                         Transition::Pop,
                         Transition::Replace(SandboxMode::new(
@@ -342,18 +348,6 @@ impl ChangeMode {
             modifiers,
             panel: Panel::new(Widget::col(vec![
                 Line("Change trip mode").small_heading().draw(ctx),
-                Widget::row(vec![
-                    "Change to trip type:".draw_text(ctx),
-                    Widget::dropdown(
-                        ctx,
-                        "to_mode",
-                        TripMode::Bike,
-                        TripMode::all()
-                            .into_iter()
-                            .map(|m| Choice::new(m.ongoing_verb(), m))
-                            .collect(),
-                    ),
-                ]),
                 Widget::row(vec![
                     "Percent of people to modify:"
                         .draw_text(ctx)
@@ -370,6 +364,19 @@ impl ChangeMode {
                     "Departing until:".draw_text(ctx),
                     AreaSlider::new(ctx, 0.25 * ctx.canvas.window_width, 0.3).named("depart to"),
                 ]),
+                Widget::horiz_separator(ctx, 0.5),
+                Widget::row(vec![
+                    "Change to trip type:".draw_text(ctx),
+                    Widget::dropdown(
+                        ctx,
+                        "to_mode",
+                        TripMode::Bike,
+                        TripMode::all()
+                            .into_iter()
+                            .map(|m| Choice::new(m.ongoing_verb(), m))
+                            .collect(),
+                    ),
+                ]),
                 Widget::row(vec![
                     Btn::text_bg2("Apply").build_def(ctx, Key::Enter),
                     Btn::text_bg2("Discard changes").build_def(ctx, Key::Escape),

sim/src/make/modifier.rs

@@ -2,7 +2,7 @@ use std::collections::BTreeSet;
 
 use rand::Rng;
 use rand_xorshift::XorShiftRng;
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 
 use abstutil::Timer;
 use geom::{Duration, Time};
@@ -11,7 +11,7 @@ use map_model::Map;
 use crate::{IndividTrip, PersonID, Scenario, SpawnTrip, TripMode};
 
 /// Transforms an existing Scenario before instantiating it.
-#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Deserialize)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Serialize, Deserialize)]
 pub enum ScenarioModifier {
     RepeatDays(usize),
     CancelPeople(usize),