80 lines
3.4 KiB
Text
80 lines
3.4 KiB
Text
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= 1: Go
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:page-pagination: next
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This is a minimal sample for Zilch's Go support, intended to show off the
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ability to edit dependencies with ease, without losing the reproducibility that
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Zilch provides.
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To start, run `zilch-cli-go -m examples/go` and see the resulting binary
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operate:
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[,console]
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----
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$ zilch-cli-go -m examples/go
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example.com/go /nix/store/wh1iaiplnkznh8x4rgqxs89qn90xaf3v-example.com_go
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$ /nix/store/wh1iaiplnkznh8x4rgqxs89qn90xaf3v-example.com_go
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1980-01-01T13:37:00.000Z INFO main/main.go:9 This is an example Go program. {"exampleString": "yes", "example": true}
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----
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---
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If, say, you find a bug (e.g. you are of the opinion the line number should come
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before the file name), this has to be patched in the logging module, which is
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provided by zap. Clone the repo (`https://github.com/uber-go/zap`). In our case
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we have it at `./zap`. To make sure the bug isn't patched in this current
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version, let's first try building the example program again with it. This can be
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done with the `--replace` command, or `-r` for short. This takes a directory
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with a `go.mod`, and prioritizes it over the version of the Go module used in
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the `go.mod` of the main module.
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[,console]
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----
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$ zilch-cli-go -m examples/go -r zap
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example.com/go /nix/store/75r8574ccq8vhsjyrr8jm9icdy5f19c1-example.com_go
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$ /nix/store/75r8574ccq8vhsjyrr8jm9icdy5f19c1-example.com_go
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1980-01-01T13:37:00.000Z INFO main/main.go:9 This is an example Go program. {"exampleString": "yes", "example": true}
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----
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Sadly, after updating, nothing changed. So we'll have to make changes. The
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filename and line number are written in `zap/zapcore/entry.go`, around line 91;
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inside `FullPath()`. After patching the function to swap them around, rerunning
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the `zilch-cli-go` command shown previously will go through and recompile only
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the changed files. So:
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[,console]
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----
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$ zilch-cli-go -m examples/go -r zap
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example.com/go /nix/store/vl6dd9d4ry7xhh31vpimjsn9khpqmxgb-example.com_go
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$ /nix/store/vl6dd9d4ry7xhh31vpimjsn9khpqmxgb-example.com_go
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1980-01-01T13:37:00.000Z INFO 9:main/main.go This is an example Go program. {"exampleString": "yes", "example": true}
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----
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As you can see, the bug is fixed, by testing with a project in a different repo!
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---
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Whenever you run `zilch-cli-go`, the script runs from scratch, not using any
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previous information. It performs a series of steps to build a build graph:
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First, it walks the `go.mod` of the main module, as well as all its
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dependencies, using the `go.sum` as a guide to ensure this all stays content-
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addressed, similar to the `go` tool. Once it has all the modules that are used
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in the program, it looks for all packages inside each of the modules. Each
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package is then analyzed for which other packages it imports, which is used to
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build Zilch-native build information.
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At this point, enough information has been gathered to build the resulting
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build graph. The main package's derivation is materialized into the Nix store,
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and with it, all its dependencies are pulled in. All its dependencies are built
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with two outputs; both the native code and the API are separately stored. This
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ensures that any changes that don't affect the interface that other packages
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depend on do not cause a butterfly effect, and stay localized to the native
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code.
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At no point does Zilch run any of this code on the local system, either. All
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builds and information gathering are done entirely inside the Nix daemon, which
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provides for a stable and sandboxed environment.
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