CARGO: fix NPE while parsing of rustc commit date

src/main/kotlin/org/rust/cargo/toolchain/RustToolchain.kt

@@ -5,6 +5,7 @@
 
 package org.rust.cargo.toolchain
 
+import com.google.common.annotations.VisibleForTesting
 import com.intellij.openapi.util.SystemInfo
 import com.intellij.openapi.util.io.FileUtil
 import com.intellij.openapi.vfs.LocalFileSystem
@@ -126,6 +127,11 @@ private fun scrapeRustcVersion(rustc: Path): RustcVersion? {
         ?.stdoutLines
         ?: return null
 
+    return parseRustcVersion(lines)
+}
+
+@VisibleForTesting
+fun parseRustcVersion(lines: List<String>): RustcVersion? {
     // We want to parse following
     //
     //  ```
@@ -147,7 +153,7 @@ private fun scrapeRustcVersion(rustc: Path): RustcVersion? {
     val versionText = releaseMatch.groups[1]?.value ?: return null
     val commitHash = find(commitHashRe)?.groups?.get(1)?.value
     val commitDate = try {
-        LocalDate.parse(find(commitDateRe)?.groups?.get(1)?.value)
+        find(commitDateRe)?.groups?.get(1)?.value?.let(LocalDate::parse)
     } catch (e: DateTimeParseException) {
         null
     }

src/test/kotlin/org/rust/cargo/toolchain/RustcVersionParsingTest.kt

@@ -0,0 +1,93 @@
+/*
+ * Use of this source code is governed by the MIT license that can be
+ * found in the LICENSE file.
+ */
+
+package org.rust.cargo.toolchain
+
+import com.intellij.util.text.SemVer.parseFromText
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.Parameterized
+import org.rust.cargo.toolchain.RustChannel.*
+import kotlin.test.assertEquals
+import java.time.LocalDate.parse as parseDate
+
+@RunWith(Parameterized::class)
+class RustcVersionParsingTest(
+    private val input: String,
+    private val expectedVersion: RustcVersion?
+) {
+
+    @Test
+    fun test() {
+        val actualVersion = parseRustcVersion(input.trimIndent().lines())
+        assertEquals(expectedVersion, actualVersion)
+    }
+
+    companion object {
+        @Parameterized.Parameters
+        @JvmStatic fun data(): Collection<Array<Any>> = listOf(
+            arrayOf("""
+                rustc 1.37.0 (eae3437df 2019-08-13)
+                binary: rustc
+                commit-hash: eae3437dfe991621e8afdc82734f4a172d7ddf9b
+                commit-date: 2019-08-13
+                host: x86_64-apple-darwin
+                release: 1.37.0
+                LLVM version: 8.0    
+            """, RustcVersion(
+                parseFromText("1.37.0")!!,
+                "x86_64-apple-darwin",
+                STABLE,
+                "eae3437dfe991621e8afdc82734f4a172d7ddf9b",
+                parseDate("2019-08-13")
+            )),
+            arrayOf("""
+                rustc 1.39.0-nightly (9af17757b 2019-09-02)
+                binary: rustc
+                commit-hash: 9af17757be1cc3f672928ecf06c40a662c5ec26d
+                commit-date: 2019-09-02
+                host: x86_64-unknown-linux-gnu
+                release: 1.39.0-nightly
+                LLVM version: 9.0     
+            """, RustcVersion(
+                parseFromText("1.39.0")!!,
+                "x86_64-unknown-linux-gnu",
+                NIGHTLY,
+                "9af17757be1cc3f672928ecf06c40a662c5ec26d",
+                parseDate("2019-09-02")
+            )),
+            arrayOf("""
+                rustc 1.38.0-beta.2 (641586c1a 2019-08-21)
+                binary: rustc
+                commit-hash: 641586c1a54f1b1740f8dd796d7501e34c044da2
+                commit-date: 2019-08-21
+                host: x86_64-apple-darwin
+                release: 1.38.0-beta.2
+                LLVM version: 9.0                
+            """, RustcVersion(
+                parseFromText("1.38.0")!!,
+                "x86_64-apple-darwin",
+                BETA,
+                "641586c1a54f1b1740f8dd796d7501e34c044da2",
+                parseDate("2019-08-21")
+            )),
+            arrayOf("""
+                rustc 1.37.0
+                binary: rustc
+                commit-hash: unknown
+                commit-date: unknown
+                host: x86_64-unknown-linux-gnu
+                release: 1.37.0
+                LLVM version: 8.0                
+            """, RustcVersion(
+                parseFromText("1.37.0")!!,
+                "x86_64-unknown-linux-gnu",
+                STABLE,
+                null,
+                null
+            ))
+        )
+    }
+}