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GoLang Dependency AnalysisPaul Buis

Ball State University

Go Programming Language

•Being developed by Google as a systems language

•Open Source

•Rapidly rising in popularity

•DevOps features to prevent• Linker errors• Deployment errors

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Go Program Structure

•A Package is 1:1 with a source directory

•An executable is 1:1 with a package named “main”

•Other packages are 1:1 with a compiled object library

•Object library contains• Type declarations needed by importing packages• Compiled object code

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Dependency Implications

•Package must be compiled after the packages in it imports packages are compiled.

•No importing of source-level “header” files.

•No possible mismatch between header and library

•Dependency graph is directed acyclic graph (DAG)

•DAG rooted at main

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Why this is interesting

• Go is not like C / C++, where• Namespaces not required to align with libraries

• Compilation order is arbitrary

• Dependencies may be cyclic

• Go is like many other “new” languages• Guarantee of acyclic dependency

• Enables use of special algorithms

• Go standard library includes parts of compiler/linker• No high-effort, low-reliability reproduction of parser, type checker, …

• Can concentrate on analysis of code rather than reproduction of standard

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Godepgraph

200-line open source tool

•Generates graph represented in GraphViz dot notatation

• Expects GraphViz dot to be used to do layout & static rendering

• Example renderings look like spaghetti & meatballs

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Standard godepgraph example

• Static GraphViz Graph

• Nodes lack details

• Poor layout• not the fault of godepgraph

Could be improved by interactivity

• Manual node positioning

• Experiment with alternative layouts

• Hiding “uninteresting” nodes

• Adding detail to crucial nodes• File names

• Last modified dates

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goviz

• Like godepgraph• Generates GraphViz graph

• Expects “dot” to generate static rendering

• Unlike godepgraph• Provides more detailed information about package

• Detail useful, but can overwhelm• User picking out important information & relationships

• Output device size and resolution

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Goviz output rendered by GraphViz “dot”

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Alternative Design

Backend – replacing godepgraph / goviz

•HTTP server written in Go

•Generates graph data as JSON

Frontend – replacing GraphViz “dot”

• Interactive webpage with JavaScript

•Graph rendered as interactive SVG

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Backend

• Initial version based on source of godepgraph & goviz• JSON output to include lots of detail

• Use Go standard library packages• go/build

• Encoding/json

• Use GoLang.org/x/tools packages• go/loader

• Use Go standard net/http package for server framework

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Front End

Interactive graph rendering to control:

• level of detail displayed for each node

• layout of graph

• which nodes are displayed

Needs to be able to save graph rendering as static image for import into team engineering documents.

Use one of many existing JavaScript graph rendering packages

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Deliverables/Milestones

•By Spring 2017 Showcase:• Completed Backend• Prototype Frontend

•By November 2017 Showcase• Delivery of completed initial version of tool

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Benefits

Immediate:

• Only if you are doing Go projects

Later Projects:

• Graph Generators for other languages

• More features: e.g., versioning