Validation framework

This pattern grew out of existing Intent data extraction code.

Goals

* abstract away the details of processing
* provide informative errors and warnings
* self documenting usage
* able to report multiple findings (warnings)
* fail assertions in acontrolled manner, not by throwing

Sample usage:
```
    fun readArgs(
       val bundle: Bundle
    ) = validateFrom(bundle::get): ValidationResult<ExampleObject> {
        val intValue = required(value<Int>("KEY_1"))
        val stringValue = required(value<String>("KEY_2"))
        val arrayValue = optional(array<String>("KEY_3"))
        val doubleValue = optional(value<Double>("KEY_4"))

        ExampleObject(intValue, stringValue, arrayValue, doubleValue)
    }
```

Bug: 300157408
Test: atest com.android.intentresolver.validation
Change-Id: I517e70df84c28e42023f19c8616804bc46884b49

2 files changed, 23 insertions, 0 deletions

diff --git a/tests/shared/Android.bp b/tests/shared/Android.bp
index dbd68b12..55188ee3 100644
--- a/tests/shared/Android.bp
+++ b/tests/shared/Android.bp
@@ -32,5 +32,6 @@ java_library {
         "hamcrest",
         "IntentResolver-core",
         "mockito-target-minus-junit4",
+        "truth"
     ],
 }
diff --git a/tests/shared/src/com/android/intentresolver/v2/validation/ValidationResultSubject.kt b/tests/shared/src/com/android/intentresolver/v2/validation/ValidationResultSubject.kt
new file mode 100644
index 00000000..1ff0ce8e
--- /dev/null
+++ b/tests/shared/src/com/android/intentresolver/v2/validation/ValidationResultSubject.kt
@@ -0,0 +1,22 @@
+package com.android.intentresolver.v2.validation
+
+import com.google.common.truth.FailureMetadata
+import com.google.common.truth.IterableSubject
+import com.google.common.truth.Subject
+import com.google.common.truth.Truth.assertAbout
+
+class ValidationResultSubject(metadata: FailureMetadata, private val actual: ValidationResult<*>?) :
+    Subject(metadata, actual) {
+
+    fun isSuccess() = check("isSuccess()").that(actual?.isSuccess()).isTrue()
+    fun isFailure() = check("isSuccess()").that(actual?.isSuccess()).isFalse()
+
+    fun value(): Subject = check("value").that(actual?.value)
+
+    fun findings(): IterableSubject = check("findings").that(actual?.findings)
+
+    companion object {
+        fun assertThat(input: ValidationResult<*>): ValidationResultSubject =
+            assertAbout(::ValidationResultSubject).that(input)
+    }
+}