context: use `IError` instead of `string` (#9758)

vlib/context/_context.v

@@ -1,19 +1,23 @@
+// This module defines the Context type, which carries deadlines, cancellation signals,
+// and other request-scoped values across API boundaries and between processes.
+// Based off:   https://github.com/golang/go/tree/master/src/context
+// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
 module context
 
 import time
 
-pub const (
+const (
 	background         = EmptyContext(0)
 	todo               = EmptyContext(1)
 
 	cancel_context_key = 'context.CancelContext'
 
 	// canceled is the error returned by Context.err when the context is canceled.
-	canceled           = 'context canceled'
+	canceled           = error('context canceled')
 
 	// deadline_exceeded is the error returned by Context.err when the context's
 	// deadline passes.
-	deadline_exceeded  = 'context deadline exceeded'
+	deadline_exceeded  = error('context deadline exceeded')
 )
 
 pub interface Context {
@@ -37,7 +41,7 @@ pub interface Context {
 	// canceled if the context was canceled
 	// or deadline_exceeded if the context's deadline passed.
 	// After err returns a non-nil error, successive calls to err return the same error.
-	err() string
+	err() IError
 	// Value returns the value associated with this context for key, or nil
 	// if no value is associated with key. Successive calls to Value with
 	// the same key returns the same result.

vlib/context/cancel.v

@@ -1,3 +1,7 @@
+// This module defines the Context type, which carries deadlines, cancellation signals,
+// and other request-scoped values across API boundaries and between processes.
+// Based off:   https://github.com/golang/go/tree/master/src/context
+// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
 module context
 
 import rand
@@ -6,7 +10,7 @@ import time
 
 pub interface Canceler {
 	id string
-	cancel(remove_from_parent bool, err string)
+	cancel(remove_from_parent bool, err IError)
 	done() chan int
 }
 
@@ -31,7 +35,7 @@ mut:
 	mutex    &sync.Mutex
 	done     chan int
 	children map[string]Canceler
-	err      string
+	err      IError
 }
 
 // with_cancel returns a copy of parent with a new done channel. The returned
@@ -52,6 +56,7 @@ fn new_cancel_context(parent Context) &CancelContext {
 		id: rand.uuid_v4()
 		context: parent
 		mutex: sync.new_mutex()
+		done: chan int{cap: 2}
 	}
 }
 
@@ -66,7 +71,7 @@ pub fn (mut ctx CancelContext) done() chan int {
 	return done
 }
 
-pub fn (mut ctx CancelContext) err() string {
+pub fn (mut ctx CancelContext) err() IError {
 	ctx.mutex.@lock()
 	err := ctx.err
 	ctx.mutex.unlock()
@@ -84,13 +89,13 @@ pub fn (ctx CancelContext) str() string {
 	return context_name(ctx.context) + '.with_cancel'
 }
 
-fn (mut ctx CancelContext) cancel(remove_from_parent bool, err string) {
+fn (mut ctx CancelContext) cancel(remove_from_parent bool, err IError) {
-	if err == '' {
+	if err.str() == 'none' {
 		panic('context: internal error: missing cancel error')
 	}
 
 	ctx.mutex.@lock()
-	if ctx.err != '' {
+	if ctx.err.str() != 'none' {
 		ctx.mutex.unlock()
 		// already canceled
 		return
@@ -141,7 +146,7 @@ fn propagate_cancel(parent Context, mut child Canceler) {
 		return
 	}
 
-	if p.err != '' {
+	if p.err.str() != 'none' {
 		// parent has already been canceled
 		child.cancel(false, p.err)
 	} else {

vlib/context/deadline.v

@@ -1,3 +1,7 @@
+// This module defines the Context type, which carries deadlines, cancellation signals,
+// and other request-scoped values across API boundaries and between processes.
+// Based off:   https://github.com/golang/go/tree/master/src/context
+// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
 module context
 
 import rand
@@ -43,7 +47,7 @@ pub fn with_deadline(parent Context, d time.Time) Context {
 		return Context(ctx)
 	}
 
-	if ctx.cancel_ctx.err() == '' {
+	if ctx.err().str() == 'none' {
 		go fn (mut ctx TimerContext, dur time.Duration) {
 			time.sleep(dur)
 			ctx.cancel(true, deadline_exceeded)
@@ -68,7 +72,7 @@ pub fn (mut ctx TimerContext) done() chan int {
 	return ctx.cancel_ctx.done()
 }
 
-pub fn (mut ctx TimerContext) err() string {
+pub fn (mut ctx TimerContext) err() IError {
 	return ctx.cancel_ctx.err()
 }
 
@@ -76,7 +80,7 @@ pub fn (ctx TimerContext) value(key string) ?voidptr {
 	return ctx.cancel_ctx.value(key)
 }
 
-pub fn (mut ctx TimerContext) cancel(remove_from_parent bool, err string) {
+pub fn (mut ctx TimerContext) cancel(remove_from_parent bool, err IError) {
 	ctx.cancel_ctx.cancel(false, err)
 	if remove_from_parent {
 		// Remove this TimerContext from its parent CancelContext's children.

vlib/context/empty.v

@@ -1,3 +1,7 @@
+// This module defines the Context type, which carries deadlines, cancellation signals,
+// and other request-scoped values across API boundaries and between processes.
+// Based off:   https://github.com/golang/go/tree/master/src/context
+// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
 module context
 
 import time
@@ -18,8 +22,9 @@ pub fn (ctx EmptyContext) done() chan int {
 	return ch
 }
 
-pub fn (ctx EmptyContext) err() string {
+pub fn (ctx EmptyContext) err() IError {
-	return ''
+	// TODO: Change this to `none`
+	return none_
 }
 
 pub fn (ctx EmptyContext) value(key string) ?voidptr {

vlib/context/err.v

@@ -0,0 +1,12 @@
+module context
+
+const none_ = IError(&None{})
+
+struct None {
+	msg  string
+	code int
+}
+
+fn (_ None) str() string {
+	return 'none'
+}

vlib/context/value.v

@@ -1,3 +1,7 @@
+// This module defines the Context type, which carries deadlines, cancellation signals,
+// and other request-scoped values across API boundaries and between processes.
+// Based off:   https://github.com/golang/go/tree/master/src/context
+// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
 module context
 
 import time
@@ -37,7 +41,7 @@ pub fn (ctx ValueContext) done() chan int {
 	return ctx.context.done()
 }
 
-pub fn (ctx ValueContext) err() string {
+pub fn (ctx ValueContext) err() IError {
 	return ctx.context.err()
 }