// addTopLevelExpression generates the source for the given expression and adds it to the
// state machine.
func (sg *stateGenerator) addTopLevelExpression(expression codedom.Expression) esbuilder.SourceBuilder {
// Generate the expression.
result := expressiongenerator.GenerateExpression(expression, expressiongenerator.AllowedSync,
sg.scopegraph, sg.positionMapper,
sg.generateMachine)
// Add any variables generated by the expression.
for _, varName := range result.Variables() {
sg.addVariable(varName)
}
// If the expression generated is asynchronous, then it will have at least one
// promise callback. In order to ensure continued execution, we have to wrap
// the resulting expression in a jump to a new state once it has finished executing.
if result.IsAsync() {
// Add $result, as it is needed below.
sg.addVariable("$result")
sg.hasAsyncJump = true
// Save the current state and create a new state to jump to once the expression's
// promise has resolved.
currentState := sg.currentState
targetState := sg.newState()
// Wrap the expression's promise result expression to be stored in $result,
// followed by a jump to the new state.
data := struct {
ResolutionStateId stateId
Snippets snippets
IsGenerator bool
}{targetState.ID, sg.snippets(), sg.isGeneratorFunction}
wrappingTemplateStr := `
$result = {{ emit .ResultExpr }};
{{ .Data.Snippets.SetState .Data.ResolutionStateId }}
{{ .Data.Snippets.Continue .Data.IsGenerator }}
`
promise := result.BuildWrapped(wrappingTemplateStr, data)
// Wrap the expression's promise with a catch, in case it fails.
catchTemplateStr := `
({{ emit .Item }}).catch(function(err) {
{{ .Snippets.Reject "err" }}
});
return;
`
currentState.pushBuilt(esbuilder.Template("tlecatch", catchTemplateStr, generatingItem{promise, sg}))
return esbuilder.Identifier("$result")
} else {
// Otherwise, the expression is synchronous and we can just invoke it.
return result.Build()
}
}
// generateResolveExpression generates the code for an expression resolution.
func (sg *stateGenerator) generateResolveExpression(resolveExpression *codedom.ResolveExpressionNode) {
// Generate the resolved expression, requiring that it is asynchronous to ensure it becomes
// a Promise.
result := expressiongenerator.GenerateExpression(resolveExpression.ChildExpression,
expressiongenerator.EnsureAsync,
sg.scopegraph, sg.positionMapper,
sg.generateMachine)
var resolutionName = ""
var rejectionName = ""
if resolveExpression.ResolutionName != "" {
resolutionName = sg.addVariable(resolveExpression.ResolutionName)
}
if resolveExpression.RejectionName != "" {
rejectionName = sg.addVariable(resolveExpression.RejectionName)
}
// Save the current state and create a new state to jump to once the expression's
// promise has resolved or rejected.
currentState := sg.currentState
sg.generateStates(resolveExpression.Target, generateNewState)
// Build the expression with an assignment of the resolved expression value assigned to
// the resolution variable (if any) and then a jump to the post-resolution state.
jumpToTarget := sg.jumpToStatement(resolveExpression.Target)
resolveData := struct {
ResolutionName string
RejectionName string
JumpToTarget string
Snippets snippets
IsGenerator bool
}{resolutionName, rejectionName, jumpToTarget, sg.snippets(), sg.isGeneratorFunction}
wrappingTemplateStr := `
{{ if .Data.ResolutionName }}
{{ .Data.ResolutionName }} = {{ emit .ResultExpr }};
{{ end }}
{{ if .Data.RejectionName }}
{{ .Data.RejectionName }} = null;
{{ end }}
{{ .Data.JumpToTarget }}
{{ .Data.Snippets.Continue .Data.IsGenerator }}
`
promise := result.BuildWrapped(wrappingTemplateStr, resolveData)
// Similarly, add a .catch onto the Promise with an assignment of the rejected error (if any)
// to the rejection variable (if any) and then a jump to the post-rejection state.
rejectData := struct {
Promise esbuilder.SourceBuilder
ResolutionName string
RejectionName string
JumpToTarget string
Snippets snippets
IsGenerator bool
}{promise, resolutionName, rejectionName, jumpToTarget, sg.snippets(), sg.isGeneratorFunction}
catchTemplateStr := `
({{ emit .Promise }}).catch(function($rejected) {
{{ if .RejectionName }}
{{ .RejectionName }} = $rejected;
{{ end }}
{{ if .ResolutionName }}
{{ .ResolutionName }} = null;
{{ end }}
{{ .JumpToTarget }}
{{ .Snippets.Continue .IsGenerator }}
});
return;
`
currentState.pushBuilt(esbuilder.Template("resolvecatch", catchTemplateStr, rejectData))
}