Merge pull request #2152 from grouville/faq

docs: add an FAQ section

docs/faq/1229-empty-buildkit-cache.md

@@ -0,0 +1,22 @@
+---
+slug: /1229/empty-buildkit-cache
+displayed_sidebar: '0.2'
+---
+
+# How to empty BuildKit's cache ?
+
+There are two ways of emptying the BuildKit cache:
+
+- Run your action with the `--no-cache` option:
+
+```console
+dagger do <your-action> --no-cache
+```
+
+- Stop and remove the buildkitd container then remove its associated volume:
+
+```console
+docker stop dagger-buildkitd ; docker rm dagger-buildkitd ; docker volume rm dagger-buildkitd
+```
+
+In 99.9% of the cases, the first solution is enough

docs/faq/1230-better-logs.md

@@ -0,0 +1,23 @@
+---
+slug: /1230/better-logs
+displayed_sidebar: '0.2'
+---
+
+# How can I have better logs ?
+
+Dagger exposes 2 logging format options:
+
+- `--log-format <auto|plain|tty|json>`
+
+The default mode is `auto`. If you want to keep each actions' logs, use the `plain` mode
+
+- `--log-level <panic|fatal|error|warn|info|debug|trace>`
+
+`debug` is useful to check whether an explicit dependency has been found between two actions and see CUE DAG at run time.
+
+You can also export these options as env variables:
+
+```console
+export DAGGER_LOG_FORMAT="plain"
+export DAGGER_LOG_LEVEL="debug"
+```

docs/faq/1231-always-execute.md

@@ -0,0 +1,28 @@
+---
+slug: /1231/always-execute
+displayed_sidebar: '0.2'
+---
+
+# How to always execute an action ?
+
+Dagger implemented a way invalidate cache for a specific action.
+
+The `docker.#Run` and `core.#Exec` definitions have an `always` field:
+
+```cue
+// If set to true, the cache will never be triggered for that specific action.
+always: bool | *false
+```
+
+Any package composed on top of it (`bash.#Run` for example) also exposes this field as it will inherit it from `docker.#Run`:
+
+```cue
+test: bash.#Run & {
+    always: true
+    ...
+}
+```
+
+:::warning
+Any dependent actions will also be retriggered
+:::

docs/faq/1232-chain-actions.md

@@ -0,0 +1,49 @@
+---
+slug: /1232/chain-actions
+displayed_sidebar: '0.2'
+---
+
+# How can I chain actions together ?
+
+Dependencies are materialized at runtime, when your Cue files are parsed and the corresponding DAG gets generated:
+
+```cue
+// Prerequisite action that runs when `test` is being called
+_dockerCLI: alpine.#Build & {
+    packages: bash: _
+}
+
+// Main action
+foo: bash.#Run & {
+    input: _dockerCLI.output // <== CHAINING of action happening here
+    script: contents: #"""
+        echo "hello"
+        """#
+}
+```
+
+On above example, `_dockerCLI` gets executed first, as the corresponding DAG shows that it is required for the action `foo` to be processed.
+
+This is the `input-output` model: `foo`'s input is `_dockerCLI`'s output.
+
+We currently do not support explicit dependencies at the moment (one of our top priority). But, if you need one, here is how you can hack your way around it:
+
+```cue
+foo: bash.#Run & {
+    input: _dockerCLI.output
+    script: contents: #"""
+        echo "hello"
+        """#
+}
+
+// Main action
+bar: bash.#Run & {
+    input: _dockerCLI.output
+    script: contents: #"""
+        echo "hello"
+        """#
+    env: HACK: "\(test.success)" // <== HACK: CHAINING of action happening here
+}
+```
+
+`foo` and `bar` are similar actions. If you do not want to rely on the `input-output` model but still want to force a dependency between them. The easiest way is to create an environment variable that relies on the other action's success

docs/faq/1233-default-values-cue.md

@@ -0,0 +1,54 @@
+---
+slug: /1233/default-values-cue
+displayed_sidebar: '0.2'
+---
+
+# Default values and optional fields
+
+When writing a Cue config, you will sometimes want to set default values in your package.
+
+The most common way you'll encounter in our codebase is: `key: type | *value`:
+
+```cue
+defaultValue: string | *"foo"
+defaultValue: bool | *false
+```
+
+You'll also encounter the `*null` default value, which is self explanatory:
+
+```cue
+// here, defaultValue either accepts a #PersonalDefinition, or stays null by default
+defaultValue: #PersonalDefinition | *null
+```
+
+To test the type of `defaultValue`, you can directly do such assertion:
+
+```cue
+if defaultValue != "foo" | if defaultValue != false | if defaultValue != null {
+    ...
+}
+ 
+if defaultValue == "foo" | if defaultValue == false | if defaultValue == null {
+    ...
+}
+```
+
+However, don't get confused with the optional fields. Optional fields check whether a key is concrete at the given scope in the DAG. You declare them with `?` at the end of their name: `foo?`.
+
+```cue
+foo?: string // 1. declare foo. It remains undefined for now
+
+foo: "bar" // 2. Now, `foo` gets concrete. The field isn't undefined anymore
+```
+
+To check on a field's concreteness, use the bottom value `_|_`:
+
+```cue
+if foo != _|_ { // if foo is not `undefined`
+    ...
+}
+ 
+if foo == _|_ { // if foo is `undefined`
+    ...
+}
+```

docs/faq/index.md

@@ -0,0 +1,33 @@
+---
+slug: /faq
+displayed_sidebar: '0.2'
+---
+
+# FAQ
+
+```mdx-code-block
+import DocCardList from '@theme/DocCardList';
+import {useDocsVersion} from '@docusaurus/theme-common';
+
+export const FaqItems = () => {
+    {/* access root category object from Docusaurus */}
+    const docsVersion = useDocsVersion();
+    {/* customProps object retrieved from sidebar.js */}
+    const faqItem = docsVersion.docsSidebars['0.2'].filter(item => item.label === 'FAQ');
+    {/* Return custom FAQ Items array */}
+    const customPropsItem = faqItem[0].customProps.items.map(customPropsItem => {
+        const result = Object.values(docsVersion.docs).filter(item => item.id === customPropsItem.docId)[0]
+        if(result)
+            return {
+                type: "link",
+                label: result.title,
+                description: result.description,
+                href: customPropsItem.href,
+                docId: customPropsItem.docId
+            }
+    })
+    return <DocCardList items={customPropsItem}/>
+}
+
+<FaqItems />
+```

website/sidebars.js

@@ -57,6 +57,20 @@ module.exports = {
       	"guides/migrate-from-dagger-0.1",
       ],
     },
+    {
+      type: "doc",
+      label: "FAQ",
+      id: "faq/index",
+      customProps: {
+        "items": [
+          { docId: "faq/empty-buildkit-cache", href: "1229/empty-buildkit-cache" },
+          { docId: "faq/better-logs", href: "1230/better-logs" },
+          { docId: "faq/always-execute", href: "1231/always-execute" },
+          { docId: "faq/chain-actions", href: "1232/chain-actions" },
+          { docId: "faq/default-values-cue", href: "1233/default-values-cue" },
+        ]
+      }
+    },
     {
       type: "category",
       label: "References",