substrate: sysinfo: Expose failed hardware requirements (#2144)

The check_hardware functions does not give us too much information as to
what is failing, so let's return the list of failed metrics, so that callers can print 
it.

This would make debugging easier, rather than try to guess which
dimension is actually failing.

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

substrate/client/sysinfo/src/sysinfo.rs

@@ -23,9 +23,11 @@ use sp_core::{sr25519, Pair};
 use sp_io::crypto::sr25519_verify;
 use sp_std::{fmt, fmt::Formatter, prelude::*};
 
+use derive_more::From;
 use rand::{seq::SliceRandom, Rng, RngCore};
 use serde::{de::Visitor, Deserialize, Deserializer, Serialize, Serializer};
 use std::{
+	fmt::Display,
 	fs::File,
 	io::{Seek, SeekFrom, Write},
 	ops::{Deref, DerefMut},
@@ -48,6 +50,37 @@ pub enum Metric {
 	DiskRndWrite,
 }
 
+/// Describes a checking failure for the hardware requirements.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct CheckFailure {
+	/// The metric that failed the check.
+	pub metric: Metric,
+	/// The expected minimum value.
+	pub expected: Throughput,
+	/// The measured value.
+	pub found: Throughput,
+}
+
+/// A list of metrics that failed to meet the minimum hardware requirements.
+#[derive(Debug, Clone, PartialEq, From)]
+pub struct CheckFailures(pub Vec<CheckFailure>);
+
+impl Display for CheckFailures {
+	fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
+		write!(formatter, "Failed checks: ")?;
+		for failure in &self.0 {
+			write!(
+				formatter,
+				"{}(expected: {}, found: {}), ",
+				failure.metric.name(),
+				failure.expected,
+				failure.found
+			)?
+		}
+		Ok(())
+	}
+}
+
 impl Metric {
 	/// The category of the metric.
 	pub fn category(&self) -> &'static str {
@@ -626,33 +659,54 @@ pub fn gather_hwbench(scratch_directory: Option<&Path>) -> HwBench {
 
 impl Requirements {
 	/// Whether the hardware requirements are met by the provided benchmark results.
-	pub fn check_hardware(&self, hwbench: &HwBench) -> bool {
+	pub fn check_hardware(&self, hwbench: &HwBench) -> Result<(), CheckFailures> {
+		let mut failures = Vec::new();
 		for requirement in self.0.iter() {
 			match requirement.metric {
 				Metric::Blake2256 =>
 					if requirement.minimum > hwbench.cpu_hashrate_score {
-						return false
+						failures.push(CheckFailure {
+							metric: requirement.metric,
+							expected: requirement.minimum,
+							found: hwbench.cpu_hashrate_score,
+						});
 					},
 				Metric::MemCopy =>
 					if requirement.minimum > hwbench.memory_memcpy_score {
-						return false
+						failures.push(CheckFailure {
+							metric: requirement.metric,
+							expected: requirement.minimum,
+							found: hwbench.memory_memcpy_score,
+						});
 					},
 				Metric::DiskSeqWrite =>
 					if let Some(score) = hwbench.disk_sequential_write_score {
 						if requirement.minimum > score {
-							return false
+							failures.push(CheckFailure {
+								metric: requirement.metric,
+								expected: requirement.minimum,
+								found: score,
+							});
 						}
 					},
 				Metric::DiskRndWrite =>
 					if let Some(score) = hwbench.disk_random_write_score {
 						if requirement.minimum > score {
-							return false
+							failures.push(CheckFailure {
+								metric: requirement.metric,
+								expected: requirement.minimum,
+								found: score,
+							});
 						}
 					},
 				Metric::Sr25519Verify => {},
 			}
 		}
-		true
+		if failures.is_empty() {
+			Ok(())
+		} else {
+			Err(failures.into())
+		}
 	}
 }