Move time proptest generators into their own crate (#829)

* Move time proptest generators into their own crate

Closes #828

This allows us to use the timestamp and DateTime generators in any other
crate in our workspace. It should help advance #822 and #821.

* Fix clippy warning

* Correct documentation example

* Update pbt-gen/src/time.rs

Co-authored-by: Thane Thomson <thane@informal.systems>

* Update pbt-gen/src/time.rs

Co-authored-by: Thane Thomson <thane@informal.systems>

* Fix typos in pbt-gen/Cargo.toml

* Rename pbt-gen crate and guard modules with feature

* Correct wording

Co-authored-by: Thane Thomson <thane@informal.systems>

Cargo.toml

@@ -9,7 +9,8 @@ members = [
     "proto",
     "rpc",
     "tendermint",
-    "testgen"
+    "testgen",
+    "pbt-gen"
 ]
 
 exclude = [

pbt-gen/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "tendermint-pbt-gen"
+version = "0.1.0"
+authors = ["Shon Feder <shon@informal.systems>"]
+edition = "2018"
+description = """
+            An internal crate providing proptest generators used across our
+            crates and not depending on any code internal to those crates.
+            """
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[features]
+
+default = ["time"]
+
+time = ["chrono"]
+
+[dependencies]
+
+chrono = { version = "0.4", features = ["serde"], optional = true}
+proptest = "0.10.1"

pbt-gen/README.md

@@ -0,0 +1,10 @@
+# PBT Gen
+
+This internal crate provides [proptest](https://github.com/AltSysrq/proptest)
+strategies and other PBT utilities used for testing.
+
+To view the documentation (which includes examples) run
+
+```sh
+cargo doc --open -p tendermint-pbt-gen
+```

pbt-gen/src/lib.rs

@@ -0,0 +1,19 @@
+//! This internal crate provides [proptest](https://github.com/AltSysrq/proptest)
+//! strategies and other PBT utilities used for testing.
+//!
+//! Conditions for inclusion in this crate are:
+//!
+//! 1. The utilities are relatively general.
+//! 2. The utilities don't rely on any code internal to the other crates of
+//! this repository.
+//!
+//! The each module of this crate (and the module's dependencies) are guarded by
+//! a feature, documented along with the module.
+//!
+//! The default features are:
+//!
+//! - "time"
+
+/// Enabled with the "time" feature:
+#[cfg(feature = "time")]
+pub mod time;

pbt-gen/src/time.rs

@@ -0,0 +1,182 @@
+//! Provides [proptest](https://github.com/AltSysrq/proptest) generators for
+//! time-like objects.
+
+use std::convert::TryInto;
+
+use chrono::{DateTime, NaiveDate, TimeZone, Timelike, Utc};
+use proptest::prelude::*;
+
+/// Any higher, and we're at seconds
+pub const MAX_NANO_SECS: u32 = 999_999_999u32;
+
+/// The most distant time in the past for which chrono produces correct
+/// times from [Utc.timestamp](chrono::Utc.timestamp).
+///
+/// See <https://github.com/chronotope/chrono/issues/537>.
+///
+/// ```
+/// use pbt_gen;
+///
+/// assert_eq!(pbt_gen::time::min_time().to_string(), "1653-02-10 06:13:21 UTC".to_string());
+/// ```
+pub fn min_time() -> DateTime<Utc> {
+    Utc.timestamp(-9999999999, 0)
+}
+
+/// The most distant time in the future for which chrono produces correct
+/// times from [Utc.timestamp](chrono::Utc.timestamp).
+///
+/// See <https://github.com/chronotope/chrono/issues/537>.
+///
+/// ```
+/// use pbt_gen;
+///
+/// assert_eq!(pbt_gen::time::max_time().to_string(), "5138-11-16 09:46:39 UTC".to_string());
+/// ```
+pub fn max_time() -> DateTime<Utc> {
+    Utc.timestamp(99999999999, 0)
+}
+
+fn num_days_in_month(year: i32, month: u32) -> u32 {
+    // Using chrono, we get the duration beteween this month and the next,
+    // then count the number of days in that duration.  See
+    // https://stackoverflow.com/a/58188385/1187277
+    let given_month = NaiveDate::from_ymd(year, month, 1);
+    let next_month = NaiveDate::from_ymd(
+        if month == 12 { year + 1 } else { year },
+        if month == 12 { 1 } else { month + 1 },
+        1,
+    );
+    next_month
+        .signed_duration_since(given_month)
+        .num_days()
+        .try_into()
+        .unwrap()
+}
+
+prop_compose! {
+    /// An abitrary [chrono::DateTime] that is between the given `min`
+    /// and `max`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use chrono::{TimeZone, Utc};
+    /// use pbt_gen;
+    /// use proptest::prelude::*;
+    ///
+    /// proptest!{
+    ///     fn rosa_luxemburg_and_octavia_butler_were_not_alive_at_the_same_time(
+    ///        time_in_luxemburgs_lifespan in pbt_gen::time::arb_datetime_in_range(
+    ///          Utc.ymd(1871, 3, 5).and_hms(0,0,0), // DOB
+    ///          Utc.ymd(1919, 1, 15).and_hms(0,0,0), // DOD
+    ///        ),
+    ///        time_in_butlers_lifespan in pbt_gen::time::arb_datetime_in_range(
+    ///          Utc.ymd(1947, 6, 22).and_hms(0,0,0), // DOB
+    ///          Utc.ymd(2006, 2, 24).and_hms(0,0,0), // DOD
+    ///        ),
+    ///     ) {
+    ///       prop_assert!(time_in_luxemburgs_lifespan != time_in_butlers_lifespan)
+    ///     }
+    /// }
+    /// ```
+    pub fn arb_datetime_in_range(min: DateTime<Utc>, max: DateTime<Utc>)(
+        secs in min.timestamp()..max.timestamp()
+    )(
+        // min mano secods is only relevant if we happen to hit the minimum
+        // seconds on the nose.
+        nano in (if secs == min.timestamp() { min.nanosecond() } else { 0 })..MAX_NANO_SECS,
+        // Make secs in scope
+        secs in Just(secs),
+    ) -> DateTime<Utc> {
+        println!(">> Secs {:?}", secs);
+        Utc.timestamp(secs, nano)
+    }
+}
+
+prop_compose! {
+    /// An abitrary [chrono::DateTime] (between [min_time] and [max_time]).
+    pub fn arb_datetime()
+        (
+            d in arb_datetime_in_range(min_time(), max_time())
+        ) -> DateTime<Utc> {
+            d
+        }
+}
+
+// The following components of the timestamp follow
+// Section 5.6 of RFC3339: https://tools.ietf.org/html/rfc3339#ref-ABNF.
+
+prop_compose! {
+    // See https://tools.ietf.org/html/rfc3339#appendix-A
+    fn arb_rfc339_time_offset()(
+        sign in "[+-]",
+        hour in 0..23u8,
+        min in 0..59u8,
+    ) -> String {
+        format!("{:}{:0>2}:{:0>2}", sign, hour, min)
+    }
+}
+
+fn arb_rfc3339_offset() -> impl Strategy<Value = String> {
+    prop_oneof![arb_rfc339_time_offset(), Just("Z".to_owned())]
+}
+
+prop_compose! {
+    fn arb_rfc3339_partial_time()(
+        hour in 0..23u8,
+        min in 0..59u8,
+        sec in 0..59u8,
+        secfrac in proptest::option::of(0..u64::MAX),
+    ) -> String {
+        let frac = match secfrac {
+            None => "".to_owned(),
+            Some(frac) => format!(".{:}", frac)
+        };
+        format!("{:0>2}:{:0>2}:{:0>2}{:}", hour, min, sec, frac)
+    }
+}
+
+prop_compose! {
+    fn arb_rfc3339_full_time()(
+        time in arb_rfc3339_partial_time(),
+        offset in arb_rfc3339_offset()
+    ) -> String {
+        format!("{:}{:}", time, offset)
+    }
+}
+
+prop_compose! {
+    fn arb_rfc3339_day_of_year_and_month(year: i32, month: u32)
+        (
+            d in 1..num_days_in_month(year, month)
+        ) -> u32 {
+            d
+        }
+}
+
+prop_compose! {
+    fn arb_rfc3339_full_date()(year in 0..9999i32, month in 1..12u32)
+        (
+            day in arb_rfc3339_day_of_year_and_month(year, month),
+            year in Just(year),
+            month in Just(month),
+        ) -> String {
+            format!("{:0>4}-{:0>2}-{:0>2}", year, month, day)
+        }
+}
+
+prop_compose! {
+    /// An aribtrary RFC3339 timestamp
+    ///
+    /// For example: `1985-04-12T23:20:50.52Z`
+    ///
+    /// The implementaiton follows
+    /// [Section 5.6 of RFC3339](https://tools.ietf.org/html/rfc3339#ref-ABNF)
+    pub fn arb_rfc3339_timestamp()(
+        date in arb_rfc3339_full_date(),
+        time in arb_rfc3339_full_time()
+    ) -> String {
+        format!("{:}T{:}", date, time)
+    }
+}

tendermint/Cargo.toml

@@ -68,3 +68,4 @@ secp256k1 = ["k256", "ripemd160"]
 [dev-dependencies]
 
 proptest = "0.10.1"
+tendermint-pbt-gen = { path = "../pbt-gen" }