From 3c8d2bbaec5c0933c2cf0302db39e715e555d428 Mon Sep 17 00:00:00 2001
From: Ulises Jeremias Cornejo Fandos <ulisesjcf_24@outlook.com>
Date: Sun, 25 Apr 2021 06:04:07 -0700
Subject: [PATCH] vlib/context: some clean up and more readable examples
 (#9868)

---
 vlib/context/README.md       | 36 ++++++------------------------------
 vlib/context/cancel.v        | 14 +++++---------
 vlib/context/deadline.v      |  2 +-
 vlib/context/deadline_test.v | 27 ++++++---------------------
 vlib/context/empty_test.v    |  6 ++----
 5 files changed, 20 insertions(+), 65 deletions(-)

diff --git a/vlib/context/README.md b/vlib/context/README.md
index fb1b02467..4743a97f1 100644
--- a/vlib/context/README.md
+++ b/vlib/context/README.md
@@ -83,15 +83,6 @@ const (
 	short_duration = 1 * time.millisecond
 )
 
-fn after(dur time.Duration) chan int {
-	dst := chan int{}
-	go fn (dur time.Duration, dst chan int) {
-		time.sleep(dur)
-		dst <- 0
-	}(dur, dst)
-	return dst
-}
-
 // This example passes a context with an arbitrary deadline to tell a blocking
 // function that it should abandon its work as soon as it gets to it.
 fn example_with_deadline() {
@@ -105,14 +96,11 @@ fn example_with_deadline() {
 		context.cancel(ctx)
 	}
 
-	after_ch := after(1 * time.second)
 	ctx_ch := ctx.done()
 	select {
-		_ := <-after_ch {
-			assert false
-		}
-		_ := <-ctx_ch {
-			assert true
+		_ := <-ctx_ch {}
+		> 1 * time.second {
+			panic('This should not happen')
 		}
 	}
 }
@@ -129,15 +117,6 @@ const (
 	short_duration = 1 * time.millisecond
 )
 
-fn after(dur time.Duration) chan int {
-	dst := chan int{}
-	go fn (dur time.Duration, dst chan int) {
-		time.sleep(dur)
-		dst <- 0
-	}(dur, dst)
-	return dst
-}
-
 // This example passes a context with a timeout to tell a blocking function that
 // it should abandon its work after the timeout elapses.
 fn example_with_timeout() {
@@ -148,14 +127,11 @@ fn example_with_timeout() {
 		context.cancel(ctx)
 	}
 
-	after_ch := after(1 * time.second)
 	ctx_ch := ctx.done()
 	select {
-		_ := <-after_ch {
-			assert false
-		}
-		_ := <-ctx_ch {
-			assert true
+		_ := <-ctx_ch {}
+		> 1 * time.second {
+			panic('This should not happen')
 		}
 	}
 }
diff --git a/vlib/context/cancel.v b/vlib/context/cancel.v
index 78ae92f06..e5aaf5f64 100644
--- a/vlib/context/cancel.v
+++ b/vlib/context/cancel.v
@@ -90,12 +90,12 @@ pub fn (ctx CancelContext) str() string {
 }
 
 fn (mut ctx CancelContext) cancel(remove_from_parent bool, err IError) {
-	if err.str() == 'none' {
+	if err is none {
 		panic('context: internal error: missing cancel error')
 	}
 
 	ctx.mutex.@lock()
-	if ctx.err.str() != 'none' {
+	if !(ctx.err is none) {
 		ctx.mutex.unlock()
 		// already canceled
 		return
@@ -129,28 +129,24 @@ fn propagate_cancel(parent Context, mut child Canceler) {
 			child.cancel(false, parent.err())
 			return
 		}
-		else {}
 	}
 	mut p := parent_cancel_context(parent) or {
 		go fn (parent Context, mut child Canceler) {
 			pdone := parent.done()
-			cdone := child.done()
 			select {
 				_ := <-pdone {
 					child.cancel(false, parent.err())
 				}
-				_ := <-cdone {}
-				else {}
 			}
 		}(parent, mut child)
 		return
 	}
 
-	if p.err.str() != 'none' {
+	if p.err is none {
+		p.children[child.id] = *child
+	} else {
 		// parent has already been canceled
 		child.cancel(false, p.err)
-	} else {
-		p.children[child.id] = *child
 	}
 }
 
diff --git a/vlib/context/deadline.v b/vlib/context/deadline.v
index 3fc050f1f..43fd056bb 100644
--- a/vlib/context/deadline.v
+++ b/vlib/context/deadline.v
@@ -47,7 +47,7 @@ pub fn with_deadline(parent Context, d time.Time) Context {
 		return Context(ctx)
 	}
 
-	if ctx.err().str() == 'none' {
+	if ctx.err() is none {
 		go fn (mut ctx TimerContext, dur time.Duration) {
 			time.sleep(dur)
 			ctx.cancel(true, deadline_exceeded)
diff --git a/vlib/context/deadline_test.v b/vlib/context/deadline_test.v
index 0f052e511..2d6a93992 100644
--- a/vlib/context/deadline_test.v
+++ b/vlib/context/deadline_test.v
@@ -6,15 +6,6 @@ const (
 	short_duration = 1 * time.millisecond
 )
 
-fn after(dur time.Duration) chan int {
-	dst := chan int{}
-	go fn (dur time.Duration, dst chan int) {
-		time.sleep(dur)
-		dst <- 0
-	}(dur, dst)
-	return dst
-}
-
 // This example passes a context with an arbitrary deadline to tell a blocking
 // function that it should abandon its work as soon as it gets to it.
 fn test_with_deadline() {
@@ -28,14 +19,11 @@ fn test_with_deadline() {
 		context.cancel(ctx)
 	}
 
-	after_ch := after(1 * time.second)
 	ctx_ch := ctx.done()
 	select {
-		_ := <-after_ch {
-			assert false
-		}
-		_ := <-ctx_ch {
-			assert true
+		_ := <-ctx_ch {}
+		> 1 * time.second {
+			panic('This should not happen')
 		}
 	}
 }
@@ -50,14 +38,11 @@ fn test_with_timeout() {
 		context.cancel(ctx)
 	}
 
-	after_ch := after(1 * time.second)
 	ctx_ch := ctx.done()
 	select {
-		_ := <-after_ch {
-			assert false
-		}
-		_ := <-ctx_ch {
-			assert true
+		_ := <-ctx_ch {}
+		> 1 * time.second {
+			panic('This should not happen')
 		}
 	}
 }
diff --git a/vlib/context/empty_test.v b/vlib/context/empty_test.v
index 8900fb58c..433d8c8ad 100644
--- a/vlib/context/empty_test.v
+++ b/vlib/context/empty_test.v
@@ -4,8 +4,7 @@ fn test_background() {
 	ctx := background()
 	assert 'context.Background' == ctx.str()
 	if _ := ctx.value('') {
-		println('This should not happen')
-		assert false
+		panic('This should never happen')
 	}
 }
 
@@ -13,7 +12,6 @@ fn test_todo() {
 	ctx := todo()
 	assert 'context.TODO' == ctx.str()
 	if _ := ctx.value('') {
-		println('This should not happen')
-		assert false
+		panic('This should never happen')
 	}
 }
-- 
2.30.2