Refactor diff command for parallel processing#82
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The diff command is a high-performance comparison utility designed to analyze changes between two DESIGN.md specifications. It loads both files concurrently using Promise.all() to reduce I/O latency, then executes the linting pipeline for each document to generate normalized design-system reports containing tokens, component definitions, and validation summaries. The command compares colors, typography, spacing, rounded values, and serialized component structures using diffMaps(), while component serialization is optimized through manual property iteration instead of Object.fromEntries() to reduce temporary allocations and garbage collection overhead. Summary deltas for errors and warnings are precomputed to avoid repeated calculations and improve readability. A regression state is automatically detected when the newer specification introduces additional warnings or errors, causing the process to exit with code 1 for CI/CD enforcement. The architecture prioritizes low memory usage, reduced heap churn, improved async concurrency, and scalable performance for large enterprise design systems with thousands of components and tokens.
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Thank you @manucian-official! I'm going to review this today. |
davideast
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davideast
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Again, thank you so much @manucian-official.
I requested a few changes but after that we should be able to merge.
| // Copyright 2026 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. |
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We need the complete license header in each file.
| name: 'diff', | ||
| description: 'Compare two DESIGN.md files and report changes.', | ||
| }, | ||
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I need to set up pre-commit hooks for linting but if you could remove the extra spaces before than that would be much appreciated.
| rounded: diffMaps(beforeReport.designSystem.rounded, afterReport.designSystem.rounded), | ||
| spacing: diffMaps(beforeReport.designSystem.spacing, afterReport.designSystem.spacing), | ||
| colors: diffMaps(beforeDS.colors, afterDS.colors), | ||
| typography: diffMaps(beforeDS.typography, afterDS.typography), |
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The extra spaces are most pronounced in this block.
| // Parallel CPU work | ||
| const [beforeReport, afterReport] = await Promise.all([ | ||
| Promise.resolve(lint(beforeContent)), | ||
| Promise.resolve(lint(afterContent)), | ||
| ]); |
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The lint() function is sync so wrapping it in a promise is extra overhead and doesn't add parallelization.
| // Parallel CPU work | |
| const [beforeReport, afterReport] = await Promise.all([ | |
| Promise.resolve(lint(beforeContent)), | |
| Promise.resolve(lint(afterContent)), | |
| ]); | |
| const beforeReport = lint(beforeContent); | |
| const afterReport = lint(afterContent); |
| }); | ||
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| function serializeComponents(components: Map<string, ComponentDef>): Map<string, Record<string, unknown>> { | ||
| function serializeComponents( |
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The original uses Object.fromEntries() which is concise and idiomatic. This changes removes it for what effectively a manual reimplementation. It's more code for the same result.
Also, .entries() is added to components.entries() but Map is already iterable. The original [key, value] pair (const [name, comp] of components) is equivalent and more concise.
| const beforeContent = await readInput(args.before); | ||
| const afterContent = await readInput(args.after); | ||
| // Parallel I/O | ||
| const [beforeContent, afterContent] = await Promise.all([ | ||
| readInput(args.before), | ||
| readInput(args.after), | ||
| ]); | ||
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| // Parallel CPU work | ||
| const [beforeReport, afterReport] = await Promise.all([ |
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This is great. readInput() is async and this is a good win for parallelization.
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The diff command is a high-performance comparison utility designed to analyze changes between two DESIGN.md specifications. It loads both files concurrently using Promise.all() to reduce I/O latency, then executes the linting pipeline for each document to generate normalized design-system reports containing tokens, component definitions, and validation summaries. The command compares colors, typography, spacing, rounded values, and serialized component structures using diffMaps(), while component serialization is optimized through manual property iteration instead of Object.fromEntries() to reduce temporary allocations and garbage collection overhead. Summary deltas for errors and warnings are precomputed to avoid repeated calculations and improve readability. A regression state is automatically detected when the newer specification introduces additional warnings or errors, causing the process to exit with code 1 for CI/CD enforcement. The architecture prioritizes low memory usage, reduced heap churn, improved async concurrency, and scalable performance for large enterprise design systems with thousands of components and tokens.