97c5f0a568
This change contains an initial implementation of closure serialization built atop V8, rather than our own custom runtime. This requires that we use a Node.js dynamic C++ module, so that we can access the V8 APIs directly. No build magic is required beyond node-gyp. For the most part, this was straight forward, except for one part: we have to use internal V8 APIs. This is required for two reasons: 1) We need access to the function's lexical closure environment, so that we may look up closure variables. Although there is a tantalizingly-close v8::Object::CreationContext, its implementation intentionally pokes through closure contexts in order to recover the Function constructor context instead. That's not what we want. We want the raw, unadulterated Function::context. 2) We need to control the lexical lookups of free variables so that they can look past chained contexts, lexical contexts, withs, and eval-style context extensions. Simply runing a v8::Script, or simulating an eval, doesn't do the trick. Hence, we need to access the unexported v8::internal::Context::Lookup function. There is a third reason which is not yet implemented: free variable calculation. I could use Esprima, or do my own scanner for free variables, but I'd prefer to simply use the V8 parser so that we're using the same JavaScript parser across all components. That too is not part of the v8.h API, so we'll need to crack it open more. To be clear, these are still exported public APIs, in proper headers that are distributed with both Node and V8. They simply aren't part of the "stable" v8.h surface area. As a result, I do expect that maintaining this will be tricky, and I'd like to keep exploring how to do this without needing the internal dependency. For instance, although this works with node-gyp just fine, we will probably be brittle across versions of Node/V8, when the internal APIs might be changing. This will introduce unfortunate versioning headaches (all, hopefully and thankfully, caught at compile-time).
37 lines
1.7 KiB
TypeScript
37 lines
1.7 KiB
TypeScript
// Copyright 2016-2017, Pulumi Corporation. All rights reserved.
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const nativeruntime = require("./native/build/Release/nativeruntime.node");
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// Closure represents the serialized form of a JavaScript serverless function.
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export interface Closure {
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code: string; // a serialization of the function's source code as text.
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runtime: string; // the language runtime required to execute the serialized code.
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environment: EnvObj; // the captured lexical environment of variables to values, if any.
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}
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// EnvObj is the captured lexical environment for a closure.
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export type EnvObj = {[key: string]: EnvEntry};
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// EnvEntry is the environment slot for a named lexically captured variable.
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export interface EnvEntry {
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json?: any; // a value which can be safely json serialized.
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closure?: Closure; // a closure we are dependent on.
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obj?: EnvObj; // an object which may contain nested closures.
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arr?: EnvEntry[]; // an array which may contain nested closures.
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}
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// serializeClosure serializes a function and its closure environment into a form that is amenable to persistence
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// as simple JSON. Like toString, it includes the full text of the function's source code, suitable for execution.
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// Unlike toString, it actually includes information about the captured environment.
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export function serializeClosure(func: Function): Closure {
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// Ensure this is an expression function.
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let funcstr: string = func.toString();
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if (funcstr.indexOf("[Function:") === 0) {
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throw new Error("Cannot serialize non-expression functions (such as definitions and generators)");
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}
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// Produce the free variables and then pass them into the native runtime.
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return <Closure><any>nativeruntime.serializeClosure(func);
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}
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