rewrite v1.3 blog post

devenv/init/.envrc

@@ -1,3 +1,3 @@
-source_url "https://raw.githubusercontent.com/cachix/devenv/95f329d49a8a5289d31e0982652f7058a189bfca/direnvrc" "sha256-d+8cBpDfDBj41inrADaJt+bDWhOktwslgoP5YiGJ1v0="
+source_url "https://raw.githubusercontent.com/cachix/devenv/82c0147677e510b247d8b9165c54f73d32dfd899/direnvrc" "sha256-7u4iDd1nZpxL4tCzmPG0dQgC5V+/44Ba+tHkPob1v2k="
 
-use devenv
+use devenv

docs/blog/posts/devenv-v1.3-instant-developer-environments-with-nix-caching.md

@@ -0,0 +1,94 @@
+---
+draft: false
+date: 2024-10-03
+authors:
+  - sandydoo
+---
+
+# devenv 1.3: Instant developer environments with Nix caching
+
+Hot on the heels of the [previous release of tasks](/blog/2024/09/24/devenv-12-tasks-for-convergent-configuration-with-nix/),
+ we're releasing devenv 1.3! 🎉
+
+This release brings precise caching to Nix evaluation, significantly speeding up developer environments.
+
+Once cached, the results of a Nix eval/build can be recalled in single-digit milliseconds.
+
+If any of the automatically-detected inputs change, the cache is invalidated and the build is performed.
+
+![Caching comparison](/assets/images/caching.gif)
+
+!!!note
+
+     If you run into any issues, run devenv with `--refresh-eval-cache` and report
+     [an issue](https://github.com/cachix/devenv/issues/new?assignees=&labels=bug&projects=&template=bug_report.md&title=).
+
+## How does it work?
+
+Behind the scenes, devenv now parses Nix's internal logs to determine which files and directories were accessed during evaluation.
+
+This approach is very much inspired by [lorri](https://github.com/nix-community/lorri) and instead of running a daemon;
+the paths, the hash of their contents, and their last-modified timestamp are stored in a SQLite database.
+
+The caching process works as follows:
+
+1. During Nix evaluation, devenv parses Nix logs for which files and directories are accessed.
+2. For each accessed path, we store:
+   - The full path
+   - A hash of the file contents
+   - The last modification timestamp
+
+This information is then saved in a SQLite database for quick retrieval.
+
+When you run a devenv command, we:
+
+1. Check the database for all previously accessed paths
+2. Compare the current file hashes and timestamps to the stored values
+3. If any differences are detected, we invalidate the cache and perform a full re-evaluation
+4. If no differences are found, we use the cached results, significantly speeding up the process
+
+This approach allows us to efficiently detect changes in your project, including:
+
+- Direct modifications to Nix files
+- Changes to imported files or directories
+- Updates to files read using Nix built-ins like `readFile` or `readDir`
+
+## Comparison with Nix's built-in flake evaluation cache
+
+Nix's built-in flake evaluation caches outputs based on the lock of the inputs,
+ignoring changes to Nix evaluation that often happen during development workflow.
+
+## Comparison with existing tools
+
+Let's take a closer look at how devenv's new caching system compares to other popular tools in the Nix ecosystem:
+
+### lorri
+
+While lorri pioneered the approach of parsing Nix's internal logs for caching,
+devenv builds on this concept, integrating caching as a built-in feature that works automatically without additional setup.
+
+### direnv and nix-direnv
+
+These tools excel at caching evaluated Nix environments, but have limitations in change detection:
+
+- Manual file watching: Users often need to manually specify which files to watch for changes.
+- Limited scope: They typically can't detect changes in deeply nested imports or files read by Nix built-ins.
+
+To leverage devenv's caching capabilities with direnv, we've updated the `.envrc` file to utilize devenv's new caching logic.
+
+If you enjoy the convenience of direnv integration into editors and reloading of your development environment make sure to update `.envrc` to:
+
+```
+source_url "https://raw.githubusercontent.com/cachix/devenv/82c0147677e510b247d8b9165c54f73d32dfd899/direnvrc" "sha256-7u4iDd1nZpxL4tCzmPG0dQgC5V+/44Ba+tHkPob1v2k="
+
+use devenv
+```
+
+## What's next?
+
+`nix develop` currently remains the last bit that's rather slow and uncachable,
+we're aiming to rewrite it to bring down overhead of cached results to sub 100ms.
+
+Pop up on [Discord](https://discord.gg/naMgvexb6q) if you have any questions,
+
+Sander