docs/howto: place data using the Go API

This adds a guide demonstrating how to replicate the effect of the cue command's --path flag using the Go API. Preview-Path: /docs/howto/place-data-go-api/ Signed-off-by: Paul Jolly <[email protected]> Change-Id: I0e5618207da2bc78cff9df715b1a4827503142dd Dispatch-Trailer: {"type":"trybot","CL":1199814,"patchset":3,"ref":"refs/changes/14/1199814/3","targetBranch":"master"}
cue-lang · Aug 28, 2024 · 6a274ce · 6a274ce
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diff --git a/content/docs/howto/place-data-go-api/en.md b/content/docs/howto/place-data-go-api/en.md
@@ -0,0 +1,142 @@
+---
+title: Placing data using the Go API
+tags: [go api]
+authors: [myitcv,jpluscplusm]
+toc_hide: true
+---
+
+{{{with _script_ "en" "set caches to speed up re-running"}}}
+export GOMODCACHE=/caches/gomodcache
+export GOCACHE=/caches/gobuild
+{{{end}}}
+
+The `cue` command allows non-CUE data to be "placed" at a specific location in
+its evaluation with the `--path`/`-l` flag.
+This guide demonstrates how to achieve the same result using the Go API.
+
+## Set up the environment
+
+{{{with step}}}
+If you don't already have CUE or Go modules, initialize them:
+
+{{{with script "en" "start modules"}}}
+cue mod init cue.example
+#ellipsis 0
+go mod init go.example
+{{{end}}}
+{{{end}}}
+
+## Create some data files
+
+{{{with step}}}
+Write some CUE code and JSON data
+(if you don't already have some code that you want to update and use):
+
+{{{with upload "en" "initial cue code"}}}
+#location left right
+-- some.cue --
+package example
+
+// The data will be placed at this location.
+input: {
+	name!:    string
+	location: *"your part of the world" | string
+}
+
+output: """
+    Hello, \(input.name)!
+    How's the weather in \(input.location)?
+    """
+-- input.json --
+{
+    "name": "Charlie"
+}
+{{{end}}}
+{{{end}}}
+
+{{{with step}}}
+Check that the data file can be combined successfully with the CUE:
+
+{{{with script "en" "test cue"}}}
+cue export . input.json --path input: -e output --out text
+{{{end}}}
+{{{end}}}
+
+## Write some Go
+
+{{{with step}}}
+Write a Go program that places the data in the `input.json` file at a specific
+location within its CUE evaluation
+(or adapt your existing code to do the same):
+
+{{{with upload "en" "go program"}}}
+#location top-left
+-- main.go --
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"cuelang.org/go/cue"
+	"cuelang.org/go/cue/cuecontext"
+	"cuelang.org/go/cue/load"
+	"cuelang.org/go/encoding/json"
+)
+
+func main() {
+	ctx := cuecontext.New()
+	// Load the package in the current directory.
+	bis := load.Instances([]string{"."}, nil)
+	v := ctx.BuildInstance(bis[0])
+
+	// Load the input data.
+	jsonBytes, err := os.ReadFile("input.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Parse the input data to a CUE expression.
+	jsonData, err := json.Extract("input.json", jsonBytes)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Place the parsed data as the value of the "input" field.
+	complete := v.FillPath(cue.ParsePath("input"), jsonData)
+
+	// Extract the string value of the "output" field and print it.
+	output := complete.LookupPath(cue.ParsePath("output"))
+	msg, _ := output.String() // We know that "output" is a string type.
+	fmt.Printf("%v\n", msg)
+}
+{{{end}}}
+{{{end}}}
+
+## Run the program
+
+{{{with step}}}
+Add a dependency on `cuelang.org/go` and ensure the Go module is tidy:
+
+{{{with script "en" "go test"}}}
+#ellipsis 0
+go get cuelang.org/go@$CUELANG_CUE_LATEST
+#ellipsis 0
+go mod tidy
+{{{end}}}
+{{{end}}}
+
+{{{with step}}}
+Run the program,
+printing the same multi-line string value that `cue` produced earlier:
+
+{{{with script "en" "go run"}}}
+go run .
+{{{end}}}
+{{{end}}}
+
+## Related content
+
+- {{< linkto/related/concept "how-cue-works-with-go" >}}
+- All pages tagged with {{< tag "go api" >}}
diff --git a/content/docs/howto/place-data-go-api/gen_cache.cue b/content/docs/howto/place-data-go-api/gen_cache.cue
@@ -0,0 +1,81 @@
+package site
+{
+	content: {
+		docs: {
+			howto: {
+				"place-data-go-api": {
+					page: {
+						cache: {
+							upload: {
+								"initial cue code": "cCDR5sNYSrEu2VXlWD62h3u6GdC/q2rCqvM8RQbYLl8="
+								"go program":       "Gzyh+JVAzI2GEWyf7DIg6z9AwsBNbpQwZIkHwJ3lyMM="
+							}
+							multi_step: {
+								hash:       "EU18HI7QMRIP19IS6GQ5IVJ8OIHKKKHASQ9BAP8DIUJCAE6864L0===="
+								scriptHash: "B2ACPKB2I7S9HP09ENHJFI1UHG1SO348DOOJ6DIDMB2U9GAQLNBG===="
+								steps: [{
+									doc:      ""
+									cmd:      "export GOMODCACHE=/caches/gomodcache"
+									exitCode: 0
+									output:   ""
+								}, {
+									doc:      ""
+									cmd:      "export GOCACHE=/caches/gobuild"
+									exitCode: 0
+									output:   ""
+								}, {
+									doc:      ""
+									cmd:      "cue mod init cue.example"
+									exitCode: 0
+									output:   ""
+								}, {
+									doc:      "#ellipsis 0"
+									cmd:      "go mod init go.example"
+									exitCode: 0
+									output: """
+											...
+
+											"""
+								}, {
+									doc:      ""
+									cmd:      "cue export . input.json --path input: -e output --out text"
+									exitCode: 0
+									output: """
+											Hello, Charlie!
+											How's the weather in your part of the world?
+
+											"""
+								}, {
+									doc:      "#ellipsis 0"
+									cmd:      "go get cuelang.org/[email protected]"
+									exitCode: 0
+									output: """
+											...
+
+											"""
+								}, {
+									doc:      "#ellipsis 0"
+									cmd:      "go mod tidy"
+									exitCode: 0
+									output: """
+											...
+
+											"""
+								}, {
+									doc:      ""
+									cmd:      "go run ."
+									exitCode: 0
+									output: """
+											Hello, Charlie!
+											How's the weather in your part of the world?
+
+											"""
+								}]
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}
diff --git a/content/docs/howto/place-data-go-api/page.cue b/content/docs/howto/place-data-go-api/page.cue
@@ -0,0 +1,3 @@
+package site
+
+content: docs: howto: "place-data-go-api": page: _
diff --git a/hugo/content/en/docs/howto/place-data-go-api/index.md b/hugo/content/en/docs/howto/place-data-go-api/index.md
@@ -0,0 +1,139 @@
+---
+title: Placing data using the Go API
+tags: [go api]
+authors: [myitcv,jpluscplusm]
+toc_hide: true
+---
+
+The `cue` command allows non-CUE data to be "placed" at a specific location in
+its evaluation with the `--path`/`-l` flag.
+This guide demonstrates how to achieve the same result using the Go API.
+
+## Set up the environment
+
+{{< step stepNumber="1" >}}
+If you don't already have CUE or Go modules, initialize them:
+
+```text { title="TERMINAL" type="terminal" codeToCopy="Y3VlIG1vZCBpbml0IGN1ZS5leGFtcGxlCmdvIG1vZCBpbml0IGdvLmV4YW1wbGU=" }
+$ cue mod init cue.example
+$ go mod init go.example
+...
+```
+{{< /step >}}
+
+## Create some data files
+
+{{< step stepNumber="2" >}}
+Write some CUE code and JSON data
+(if you don't already have some code that you want to update and use):
+
+{{< code-tabs >}}
+{{< code-tab name="some.cue" language="cue" area="left" >}}
+package example
+
+// The data will be placed at this location.
+input: {
+	name!:    string
+	location: *"your part of the world" | string
+}
+
+output: """
+    Hello, \(input.name)!
+    How's the weather in \(input.location)?
+    """
+{{< /code-tab >}}{{< code-tab name="input.json" language="json" area="right" >}}
+{
+    "name": "Charlie"
+}
+{{< /code-tab >}}{{< /code-tabs >}}
+{{< /step >}}
+
+{{< step stepNumber="3" >}}
+Check that the data file can be combined successfully with the CUE:
+
+```text { title="TERMINAL" type="terminal" codeToCopy="Y3VlIGV4cG9ydCAuIGlucHV0Lmpzb24gLS1wYXRoIGlucHV0OiAtZSBvdXRwdXQgLS1vdXQgdGV4dA==" }
+$ cue export . input.json --path input: -e output --out text
+Hello, Charlie!
+How's the weather in your part of the world?
+```
+{{< /step >}}
+
+## Write some Go
+
+{{< step stepNumber="4" >}}
+Write a Go program that places the data in the `input.json` file at a specific
+location within its CUE evaluation
+(or adapt your existing code to do the same):
+
+{{< code-tabs >}}
+{{< code-tab name="main.go" language="go" area="top-left" >}}
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"cuelang.org/go/cue"
+	"cuelang.org/go/cue/cuecontext"
+	"cuelang.org/go/cue/load"
+	"cuelang.org/go/encoding/json"
+)
+
+func main() {
+	ctx := cuecontext.New()
+	// Load the package in the current directory.
+	bis := load.Instances([]string{"."}, nil)
+	v := ctx.BuildInstance(bis[0])
+
+	// Load the input data.
+	jsonBytes, err := os.ReadFile("input.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Parse the input data to a CUE expression.
+	jsonData, err := json.Extract("input.json", jsonBytes)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Place the parsed data as the value of the "input" field.
+	complete := v.FillPath(cue.ParsePath("input"), jsonData)
+
+	// Extract the string value of the "output" field and print it.
+	output := complete.LookupPath(cue.ParsePath("output"))
+	msg, _ := output.String() // We know that "output" is a string type.
+	fmt.Printf("%v\n", msg)
+}
+{{< /code-tab >}}{{< /code-tabs >}}
+{{< /step >}}
+
+## Run the program
+
+{{< step stepNumber="5" >}}
+Add a dependency on `cuelang.org/go` and ensure the Go module is tidy:
+
+```text { title="TERMINAL" type="terminal" codeToCopy="Z28gZ2V0IGN1ZWxhbmcub3JnL2dvQHYwLjEwLjAKZ28gbW9kIHRpZHk=" }
+$ go get cuelang.org/[email protected]
+...
+$ go mod tidy
+...
+```
+{{< /step >}}
+
+{{< step stepNumber="6" >}}
+Run the program,
+printing the same multi-line string value that `cue` produced earlier:
+
+```text { title="TERMINAL" type="terminal" codeToCopy="Z28gcnVuIC4=" }
+$ go run .
+Hello, Charlie!
+How's the weather in your part of the world?
+```
+{{< /step >}}
+
+## Related content
+
+- {{< linkto/related/concept "how-cue-works-with-go" >}}
+- All pages tagged with {{< tag "go api" >}}
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		package site

		content: docs: howto: "place-data-go-api": page: _