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Changes from statik to go:embed for example and extension templates (#…
…129) This reduces build complexity by eliminating a generation step with go:embed. This implicitly reduces tech debt even more because not only were we using a stalled project, statik, but also a fork of it. go:embed is not perfect, as it disallows the file name go.mod. The workaround is to rename it to go.mod_ per golang/go#45197. While this is imperfect an if-statement is a far better punch than a dependency on a fork of a stalled project which also requires a codegen step. Co-authored-by: Takeshi Yoneda <takeshi@tetrate.io> Signed-off-by: Adrian Cole <adrian@tetrate.io>
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@@ -3,6 +3,3 @@ dist | |
| /getenvoy | ||
| /build/ | ||
| .idea | ||
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| # code generated by `github.com/rakyll/statik` | ||
| statik.go | ||
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| # Notable Rationale | ||
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| ## go:embed for embedding example and init templates | ||
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| This project resolves templates into working examples or extensions via `getenvoy example add` and | ||
| `getenvoy extension init`. Input [example](data/example/init/templates) and [extension](data/extension/init/templates) | ||
| templates are embedded in the `getenvoy` binary for user convenience. | ||
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| We implement embedding with a Go 1.16+ directive `//go:embed templates/*`, which presents an `fs.FS` interface of the | ||
| directory tree. Using this requires no extra build steps. Ex. `go build -o getenvoy ./cmd/getenvoy/main.go` works. | ||
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| However, there are some constraints to understand. It is accepted that while imperfect, this solution is an acceptable | ||
| alternative to a custom solution. | ||
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| ### Embedded files must be in a sub-path | ||
| The go source file embedding content via `go:embed` must reference paths in the current directory tree. In other words, | ||
| paths like `../../templates` are not allowed. | ||
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| This means we have to move the embedded directory tree where code refers to it, or make an accessor utility for each | ||
| directory root. We use the latter pattern, specifically here: | ||
| * [data/example/init/templates.go](data/example/init/templates.go) | ||
| * [data/extension/init/templates.go](data/extension/init/templates.go) | ||
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| See https://pkg.go.dev/embed#hdr-Directives for more information. | ||
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| ### Limitations of `go:embed` impact extension init templates | ||
| `getenvoy extension init` creates a workspace directory for a given category and programming language. Some constraints | ||
| of `go:embed` impact how these template directories are laid out, and the workarounds are file rename in basis. The | ||
| impacts are noted below for information and future follow-up: | ||
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| #### `go:embed` doesn't traverse hidden directories, but Rust projects include a hidden directory | ||
| Our Rust examples use [Cargo](https://doc.rust-lang.org/cargo/reference/config.html) as a build tool. This stores | ||
| configuration in a hidden directory `.cargo`. As of Go 1.16, hidden directories are not yet supported with `go:embed`. | ||
| See https://github.com/golang/go/issues/43854 | ||
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| #### `go:embed` stops traversing at module boundaries, and TinyGo examples look like sub-modules | ||
| Go modules need to be built from the zip-file uploaded to the mirror. This implies `go:embed` must refer to the | ||
| current module. https://github.com/golang/go/issues/45197 explains embedding stops traversing when it encounters a | ||
| `go.mod` file, and there is no plan to change this. | ||
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| This presents a challenge with TinyGo templates, which except for parameterization like `module {{ .Extension.Name }}`, | ||
| appear as normal go modules (ex `go.mod`) files. When `go:embed` encounters a `go.mod` file, it stops traversing. If we | ||
| didn't work around this, no TinyGo project would end up in the embedded filesystem. | ||
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| The workaround is to rename the template `go.mod` to `go.mod_`, but this introduces a couple glitches: | ||
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| * TinyGo extension templates imports appear in the root project after running `go mod tidy` | ||
| * As of the writing, there is only one github.com/tetratelabs/proxy-wasm-go-sdk | ||
| * TinyGo extension templates can't be run from their directory without temporarily renaming `go.mod_` back to `go.mod` | ||
| * To do this anyway, you'd need to fix any template variables like `module {{ .Extension.Name }}` | ||
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| ### Former solution | ||
| In the past, we embedded via [statik](https://github.com/rakyll/statik). This is a code generation solution which | ||
| encodes files into internal variables. Entry-points use an `http.FileSystem` to access the embedded files. | ||
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| This solution worked well, except that it introduced build complexity. Code generation required an `init` phase in the | ||
| `Makefile`, as well lint exclusions. This implied steps for developers to remember and CI to invoke. | ||
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| It also introduced maintenance and risk as the statik library stalled. This project ended up pinned to a personal fork | ||
| in order to work around unmerged pull requests. | ||
| ``` | ||
| replace github.com/rakyll/statik => github.com/yskopets/statik v0.1.8-0.20200501213002-c2d8dcc79889 | ||
| ``` | ||
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| Go 1.16's `go:embed` has limitations of its own, but brings with it shared understanding. While we may need workarounds | ||
| to some issues, those issues are understood by the go community. `go:embed` does not require our maintenance, nor has | ||
| any key person risk. |
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| // Copyright 2021 Tetrate | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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| package init | ||
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| import ( | ||
| "embed" | ||
| "io/fs" | ||
| ) | ||
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| // templatesFs includes only the relative path of "templates". | ||
| // | ||
| // See RATIONALE.md for more information on embedding | ||
| //go:embed templates/* | ||
| var templatesFs embed.FS | ||
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| // GetTemplates returns the templates directory as a filesystem | ||
| func GetTemplates() fs.FS { | ||
| f, err := fs.Sub(templatesFs, "templates") | ||
| if err != nil { | ||
| panic(err) // unexpected or a typo | ||
| } | ||
| return f | ||
| } |
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| // Copyright 2021 Tetrate | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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| package init | ||
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| import ( | ||
| "embed" | ||
| "io/fs" | ||
| ) | ||
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| // templatesFs includes only the relative path of "templates". | ||
| // | ||
| // See RATIONALE.md for more information on embedding | ||
| //go:embed templates/* | ||
| var templatesFs embed.FS | ||
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| // GetTemplates returns the templates directory as a filesystem | ||
| func GetTemplates() fs.FS { | ||
| f, err := fs.Sub(templatesFs, "templates") | ||
| if err != nil { | ||
| panic(err) // unexpected or a typo | ||
| } | ||
| return f | ||
| } |
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| @@ -1,2 +1,4 @@ | ||
| # We rename .cargo to cargo See /RATIONALE.md for why | ||
| .cargo | ||
| Cargo.lock | ||
| target/ |
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| @@ -1 +1,4 @@ | ||
| build/ | ||
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| # We rename go.mod to go.mod_ See /RATIONALE.md for why | ||
| go.mod |
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