Terraform Resource Generator Skill

Generate new Terraform resources and data sources by learning from existing patterns in the codebase.

Tooling Rule (read first)

Always drive generation, formatting, and linting through Task:

• task generate — generates code and runs task fmt automatically at the end
• task fmt — formats Go, Terraform, and whitespace
• task lint — runs all linters

Do NOT use go run ./generators/..., go generate, gofmt, goimports, golangci-lint, or make for these workflows. See AGENTS.md and Taskfile.dist.yml (run task --list) for the full command surface.

Overview

The generator creates Terraform resources by combining:

1. OpenAPI Spec (openapi.json) - Aiven's API schema
2. YAML Definitions (definitions/aiven_*.yml) - Configuration for resource generation

Note: This skill is the canonical reference for YAML syntax, adapter API, and implementation patterns. The tf-resource-migration skill builds on this for migrating existing SDK resources.

Generated outputs per resource:

• zz_resource.go / zz_datasource.go - Terraform schema + internal schema
• zz_view.go - CRUD operation handlers, ResourceOptions, DataSourceOptions
• examples/resources/*/import.sh - Import command examples

Generated aggregated output:

• internal/plugin/zz_provider.go - Provider resource/datasource registry

User Interaction Pattern

When the user requests a new resource, gather requirements BEFORE starting:

First Question (REQUIRED)

ALWAYS start by asking what type of Terraform component is needed:

Use the AskUserQuestion tool with these options:

• Both resource and data source - Full CRUD resource + read-only data source
• Resource only - Just the resource (create, read, update, delete)
• Data source only - Read-only data source

Additional Information to Gather

1. Resource name - What API resource/endpoint? (e.g., "MySQL database", "Kafka topic")
2. Scope - Project-level, service-level, organization-level?

Discovery Process

1. Update OpenAPI spec first by running task get-spec to ensure you have the latest API schema
2. Search OpenAPI spec for operation IDs
3. Show the user what you found and ask for confirmation
4. Find similar resources in definitions/ and show them
5. Clarify specifics if needed (composite ID, fields to exclude/rename, custom modifiers)

When NOT to Ask

• If the user provided specific operation IDs -> proceed
• If the user provided a complete YAML definition -> proceed
• If it's a modification to existing definition -> read the file and proceed

Confirmation Before Generation

Always summarize what you're about to create before proceeding.

Learning from Existing Resources

CRITICAL: Before creating a new resource, ALWAYS search for similar existing resources to learn patterns:

# Find all YAML definitions
ls definitions/aiven_*.yml

# Find resources with similar client handlers
grep -l "clientHandler: service" definitions/aiven_*.yml

# Find resources with custom modifiers
grep -l "expandModifier: true" definitions/aiven_*.yml

# Find composite ID examples
grep -l "idAttributeComposed:" definitions/aiven_*.yml

Key files to reference:

• definitions/.schema.yml - Complete YAML schema specification
• definitions/aiven_*.yml - Real working examples
• Existing generated code in internal/plugin/service/*/zz_*.go

Generation Workflow

1. Update OpenAPI Spec

Always start by downloading the latest API schema:

task get-spec

2. Find the API Operations

Search OpenAPI spec for operation IDs:

jq '.paths | to_entries[] | .value | to_entries[] | .value.operationId' openapi.json | grep -i "keyword"

Common patterns: ResourceCreate, ResourceGet, ResourceUpdate, ResourceDelete, ResourceList

3. Find a Similar Resource

Search definitions/ for a resource with similar characteristics:

• Same client handler (project, service, organization, etc.)
• Similar ID structure (single vs composite)
• Similar operations (CRUD, list-based reads, etc.)

Read that YAML file to understand the pattern.

4. Create Your YAML Definition

File: definitions/aiven_my_resource.yml

IMPORTANT: Definition files MUST have the aiven_ prefix. The filename (without .yml) becomes the resource name directly: aiven_my_resource.yml -> resource aiven_my_resource.

Start minimal:

# yaml-language-server: $schema=.schema.yml
location: internal/plugin/service/myresource
operations:
  - id: OperationIDFromOpenAPI
    type: create|read|update|delete
resource:
  description: "..."
idAttributeComposed: [field1, field2]
clientHandler: project

5. Generate and Iterate

task generate       # Generate code
task build          # Build to check for errors
task lint           # Check code quality

Review generated zz_*.go files. Refine YAML definition as needed.

YAML Definition Reference

Top-Level Fields

IMPORTANT: Always check definitions/.schema.yml for the complete, authoritative schema specification.

Common fields:

• location - Package path (e.g., internal/plugin/service/mysql)
• operations - Array of CRUD operations (id, type, resultKey, etc.)
• resource / datasource - Configuration metadata
• idAttributeComposed - Fields that compose the ID (e.g., [project, service_name])
• clientHandler - API client type: project, service, organization, organizationbilling, etc.
• remove - Fields to exclude from schema (exact paths or glob patterns)
• rename - Field name mappings (API field -> Terraform field)
• schema - Schema customizations (types, validation, behavior)
• expandModifier / flattenModifier / planModifier - Enable custom Go modifiers
• version - Schema version (for state upgrades)
• beta - Mark resource as beta (requires PROVIDER_AIVEN_ENABLE_BETA env var)
• limitedAvailability - Mark resource as limited availability
• legacyTimeouts - Enable SDK v2-style timeout blocks

Resource Configuration

resource:
  description: "..."
  deprecationMessage: "..."
  importIDFormats:                 # Optional docs-only override for resources with multiple import forms
    - PROJECT/RESOURCE_ID
    - PROJECT/RESOURCE_ID/REGION
  terminationProtection: true # Check field before delete
  stateAttribute: state # Terraform attribute polled after Create/Update/Delete
  refreshStateDesired: [ACTIVE, PENDING_PEER] # Call Read after Create/Update and wait for state convergence
  refreshStateFailed: [ERROR, DELETED]
  refreshStateDelay: "15s" # Wait before Read
  removeMissing: true # Remove from state on 404
  deleteStateDesired: [DELETED] # Poll Read after Delete until the resource reaches its terminal state

importIDFormats generates every listed form in both the resource's Import documentation and examples/resources/<resource>/import.sh. It does not change IDFields or runtime import parsing. Omit it when the single import form can be derived from idAttributeComposed.

refreshStateExists: true enables a post-Create/Update Read that completes on the first successful Read, retrying transient 404/403 errors. To also wait for an attribute value, set stateAttribute plus refreshStateDesired and optional refreshStateFailed instead — desired already includes that exists retry. Values within each list use OR semantics. A desired value completes the refresh, and any failed value stops it immediately. Values in neither list are treated as pending and retried until the operation timeout.

stateAttribute names a top-level computed-only attribute; the generator rejects anything else. When the value to wait for lives elsewhere — nested in a collection, spread over several attributes, or derived — keep refreshStateExists: true and set ResourceOptions.RefreshStateCheck in init(). It runs after each Read of the post-Create/Update refresh only (never during plain Read, import, or a data source read), and its error decides what happens next: adapter.ErrRefreshStateFailed stops the refresh, and any other error means "not converged yet" and is retried with the same backoff as a transient Read error.

// The status lives inside a nested collection, out of reach of the declarative condition.
// Do not index with Get("file_info.0.file_status"): Get panics when the list is still empty.
func init() {
    ResourceOptions.RefreshStateCheck = fileIsReady
}

func fileIsReady(d adapter.ResourceData) error {
    list, _ := d.Get("file_info").([]any)
    if len(list) == 0 {
        return fmt.Errorf("jar file status is not ready: %q", "")
    }
    info, _ := list[0].(map[string]any)
    status, _ := info["file_status"].(string)
    switch status {
    case "READY":
        return nil
    case "FAILED":
        return fmt.Errorf("%w: jar file verification failed", adapter.ErrRefreshStateFailed)
    }
    return fmt.Errorf("jar file status is not ready: %q", status)
}

Prefer the declarative form: reach for RefreshStateCheck only when the condition cannot be expressed as desired/failed values of one top-level attribute. See internal/plugin/service/flink/jarversion/jarversion.go and internal/plugin/serviceuser for reference implementations.

deleteStateGone: true enables the delete poller and completes when Read returns 404. deleteStateDesired waits until stateAttribute matches any listed value; a 404 also completes (gone is implied). Delete is re-issued while it errors (for example 409 from dependents still detaching); once Delete succeeds, only Read is polled. Omit both to delete without polling.

Values are validated against the field's enum when one is declared. stateAttribute is required when refreshStateDesired or deleteStateDesired is set.

Examples:

# Wait until the API 404s; no observable terminal state (e.g. aiven_azure_privatelink).
deleteStateGone: true

# Soft-delete API reports state: DELETED, and dependents may still be detaching
# (e.g. aiven_project_vpc, aiven_organization_vpc).
stateAttribute: state
deleteStateDesired: [DELETED]

Prefer deleteStateGone or deleteStateDesired over a hand-written delete disableView + custom poller whenever the terminal condition is "gone (404)" and/or a fixed attribute value. Keep a custom delete view only for genuinely bespoke flows (e.g. a cancel-then-delete state machine).

Datasource Configuration

datasource:
  description: "..."
  deprecationMessage: "..."

For alternative lookup keys (e.g. look up by name instead of id), see Data Source with Alternative Lookup Key below.

Operations Configuration

Each operation maps a Terraform action to an OpenAPI operation ID:

operations:
  - id: OperationIDFromOpenAPI
    type: create|read|update|delete
    disableView: true               # Don't generate view function (for custom override)
    datasourceLookup: true          # Inline this read op as readView's id-empty branch on
                                    # the data source (requires resultListLookupKeys).
                                    # See "Data Source with Alternative Lookup Key" below.
    resultIDField: OrganizationId   # Go field on the lookup result that holds the
                                    # primary id. When set, the lookup only resolves
                                    # the id, then control falls through to the canonical
                                    # read body in the same readView. Requires
                                    # datasourceLookup + resultListLookupKeys.
    resultKey: nested_field          # Extract from response.nested_field (schema/JSON path,
                                     # used at generation time to scope the OpenAPI schema)
    resultKeyField: GoField          # Go field name on the client response to drill into at
                                     # runtime, e.g. d.Flatten(rsp.GoField). Use when the Go
                                     # client doesn't strip an extra wrapper exposed by the API
                                     # (response is {accessors: {aws: {...}}} but the client
                                     # returns *CMKAccessorsListOut, so set resultKeyField: Aws).
                                     # When combined with resultListLookupKeys, points at the
                                     # list to search (e.g. resultKeyField: ConnectionPools).
    resultToKey: wrapper_key         # Wrap response as {wrapper_key: ...}
    resultListLookupKeys:            # For list responses
      APIField: terraform_field      # Match items by field

Find examples: grep -A 5 "operations:" definitions/aiven_*.yml

Removing Fields

remove drops attributes the resource should not expose. Entries are matched against the attribute's OpenAPI path, where nested attributes are slash-separated:

remove:
  - update_time # top-level attribute
  - plans/node_count # attribute nested under "plans"

Entries are glob patterns. * and ? match within a single path segment, ** matches across segments, and a pattern with no wildcards is an exact match:

remove:
  - "azure_*" # every top-level attribute with that prefix
  - "*google*" # every top-level attribute containing "google"
  - "**/errors" # "errors" at any depth

Quote glob patterns — an unquoted leading * is an alias reference in YAML and fails to parse.

Reach for a glob when the removed attributes share an obvious naming pattern, most often a cloud provider that the resource does not support. Some Aiven endpoints serve every provider from one schema, so a provider-specific resource has to drop the rest. A glob keeps doing that when the API grows new fields, whereas an explicit list silently lets them into the schema on the next task generate. See definitions/aiven_byoc_aws_entity.yml for this pattern.

Globs only match attribute names, not descriptions or enum values, so a cloud_provider attribute whose enum lists azure is unaffected by "*azure*".

Schema Customization

Override generated schema fields:

schema:
  field_name:
    type: string|integer|number|boolean|array|arrayOrdered|object
    description: "..."
    required: true|false
    computed: true|false
    sensitive: true|false
    writeOnly: true|false
    forceNew: true|false           # Triggers replacement
    useStateForUnknown: true|false # Preserve prior state during planning
    enum: [val1, val2]
    minimum: 1
    maximum: 100
    conflictsWith: [other_field]
    exactlyOneOf: [field_a, field_b]
    atLeastOneOf: [field_a, field_b]
    alsoRequires: [other_field]
    default: value
    dropDefault: true              # Migration workaround, see tf-resource-migration. Drops the OpenAPI default
    deprecationMessage: "..."

Important: Use arrayOrdered (list) for complex objects, not array (set). Sets cause performance issues.

Blocks vs attributes: a nested collection of objects renders as a block, unless it is read-only all the way down — then it renders as a computed nested attribute (Item.RendersAsAttribute). Blocks cannot be computed, so a read-only block could never hold the values the API returns without diffing forever. Making a single nested field optional flips the whole collection back to a block, which changes the syntax users must write, so do that deliberately. Data sources always use blocks.

An object is a one-element list in either form (Item.TFType), which is the SDKv2 state shape. Due for removal in v5.0.0: an object becomes a single nested value, dropping the SizeAtMost(1) validator, the Max: 1 label and .0 indexing. The sites carrying it are marked todo: ... v5.0.0. Generated examples use attribute assignment (file_info = [{ ... }]) for computed nested attributes, not block syntax.

Find examples: grep -A 10 "schema:" definitions/aiven_*.yml

Generated View Structure

The generator produces zz_view.go with this structure:

const typeName = "aiven_my_resource"

func idFields() []string {
    return []string{"project", "service_name", "resource_name"}
}

var ResourceOptions = adapter.ResourceOptions{
    Create:   createView,
    Delete:   deleteView,
    IDFields: idFields(),
    Read:     readView,
    RefreshState: &adapter.RefreshStateCondition{
        Attribute: "state",
        Desired: []string{"ACTIVE", "PENDING_PEER"},
        Failed:  []string{"ERROR", "DELETED"},
    },
    RefreshStateDelay: adapter.MustParseDuration("15s"),
    RemoveMissing:     true,
    Schema:            resourceSchema,
    SchemaInternal:    resourceSchemaInternal(),
    TypeName:          typeName,
}

var DataSourceOptions = adapter.DataSourceOptions{
    IDFields:       idFields(),
    Read:           readView,
    Schema:         datasourceSchema,
    SchemaInternal: datasourceSchemaInternal(),
    TypeName:       typeName,
}

CRUD function signature (all views follow this pattern):

func createView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error
func readView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error
func updateView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error
func deleteView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error

ResourceOptions Additional Fields

Beyond basic CRUD, ResourceOptions supports:

• ModifyPlan — implements resource.ResourceWithModifyPlan (separate from planModifier in YAML)
• ValidateConfig — implements resource.ResourceWithValidateConfig
• ConfigValidators — implements resource.ResourceWithConfigValidators
• RefreshStateCheck — post-Create/Update convergence check that refreshState can't express (see Resource Configuration)

ResourceData Interface

All views and modifiers interact with Terraform state through adapter.ResourceData:

type ResourceData interface {
    Get(key string) any              // Get from plan, then config, then state
    GetOk(key string) (any, bool)    // Get with existence check
    GetState(key string) any         // Get specifically from state
    HasChange(key string) bool       // Plan value differs from state
    Set(key string, value any) error // Set a value in current state
    SetID(parts ...string) error     // Set composite ID
    ID() string                      // Get the "id" field
    IsNewResource() bool             // True if ID is empty
    RequiresReplace(keys ...string)  // Force replacement over attributes (ModifyPlan only)
    Schema() *Schema                 // Access internal schema
    Expand(out any, modifiers ...MapModifier) error   // Plan -> API request
    Flatten(in any, modifiers ...MapModifier) error    // API response -> state
}

Behavior by Operation

CRITICAL: ResourceData behaves differently depending on the CRUD operation:

• Create: d.Get() reads from plan, then config. No state available.
• Update: d.Get() reads from plan, then config, then state (for ID fields only). d.GetState() reads from prior state. d.HasChange() compares plan vs state.
• Read/Delete: d.Get() reads from state. No plan available.

This matters when writing modifiers:

• In flattenModifier, d.Get("field") returns the current state value (from plan during Create/Update, from state during Read)
• In expandModifier, d.Get("field") returns the plan value (what the user configured)
• Use d.HasChange("field") to detect if a field was modified (Update only)

Custom Modifiers

For complex data transformations, enable modifiers in YAML:

expandModifier: true      # TF state -> API request
flattenModifier: true     # API response -> TF state
planModifier: true        # Pre-process state before read API call

Then implement functions in a .go file in the resource package.

expandModifier / flattenModifier

Transform data between Terraform state and API request/response formats.

Signature:

func expandModifier(ctx context.Context, client avngen.Client) adapter.MapModifier
func flattenModifier(ctx context.Context, client avngen.Client) adapter.MapModifier

Where MapModifier is:

type MapModifier func(d ResourceData, dto map[string]any) error

• d — the adapter.ResourceData interface for accessing plan/state/config values
• dto — the raw map being sent to or received from the API

Example — nested API field (pg_allow_replication stored as access_control.pg_allow_replication in API but exposed top-level in TF):

func expandModifier(_ context.Context, _ avngen.Client) adapter.MapModifier {
    return func(d adapter.ResourceData, dto map[string]any) error {
        if v, ok := d.GetOk("pg_allow_replication"); ok {
            dto["access_control"] = map[string]any{"pg_allow_replication": v}
            delete(dto, "pg_allow_replication")
        }
        return nil
    }
}

func flattenModifier(_ context.Context, _ avngen.Client) adapter.MapModifier {
    return func(d adapter.ResourceData, dto map[string]any) error {
        if v, ok := dto["access_control"]; ok {
            dto["pg_allow_replication"] = v.(map[string]any)["pg_allow_replication"]
            delete(dto, "access_control")
        }
        return nil
    }
}

Composing multiple modifiers with adapter.ComposeMapModifiers():

func expandModifier(ctx context.Context, client avngen.Client) adapter.MapModifier {
    return adapter.ComposeMapModifiers(
        getFullCardID(ctx, client),
        expandParentID(ctx, client),
        ExpandEmails("billing_emails"),
    )
}

Find examples: grep -l "flattenModifier\|expandModifier" internal/plugin/service/**/*.go

planModifier

Runs at the start of the generated readView, before the API call. Use it to pre-process or fix up state so the read has all the data it needs.

Signature:

func planModifier(ctx context.Context, client avngen.Client, d adapter.ResourceData) error

When to use:

• A renamed ID field (rename: {id: deployment_id}) isn't in old SDK state — extract it from the composite id
• A field needs to be resolved before the read (e.g., name -> ID lookup via API)
• Any state pre-processing required before the generated read API call

How it works: Setting planModifier: true in YAML causes the generator to insert planModifier(ctx, client, d) at the top of readView:

// generated readView
func readView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error {
    err := planModifier(ctx, client, d)  // <-- inserted by generator
    if err != nil {
        return err
    }
    // ... API call using d.Get() fields
}

Reference implementations:

• internal/plugin/service/billinggroup/billinggroup.go — extracts billing_group_id from composite id for SDK backward compat
• internal/plugin/service/flink/deployment/deployment.go — extracts deployment_id from composite id for SDK backward compat

For name -> ID resolution in data sources, use the generated datasourceLookup pattern instead of a hand-written planModifier. See Data Source with Alternative Lookup Key.

modifyPlan

Despite the similar name, resource.modifyPlan: true has nothing to do with planModifier: it wires the package's modifyPlan function as the resource's ResourceWithModifyPlan handler, which the framework calls on every plan (except a destroy plan).

Signature:

func modifyPlan(ctx context.Context, client avngen.Client, d adapter.ResourceData) error

When to use:

• Plan-time checks that need prior state, e.g. forbidding a decrease in a numeric attribute (d.GetState vs d.Get)
• Computing a plan value the configuration cannot express, e.g. hashing a file the resource uploads

Whatever modifyPlan writes with d.Set becomes the planned value, which is the equivalent of SDKv2's CustomizeDiff + SetNew. Only computed attributes may be written: Terraform rejects a plan whose value for a configured attribute differs from the configuration.

d.RequiresReplace("attr") marks attributes whose planned value forces the resource to be replaced. Schema plan modifiers (forceNew: true -> RequiresReplace()) run before modifyPlan, so they compare a value it has not written yet: a computed value produced here needs d.RequiresReplace to have any effect. Marking an unknown attribute panics.

// A version is immutable, so edited file content can only go into a new one.
func modifyPlan(_ context.Context, _ avngen.Client, d adapter.ResourceData) error {
    checksum, err := fileChecksum(d.Get("source").(string))
    if err != nil {
        return err
    }

    if !d.IsNewResource() && checksum != d.GetState(sourceChecksumField) {
        d.RequiresReplace(sourceChecksumField)
    }

    return d.Set(sourceChecksumField, checksum)
}

Reference implementations:

• internal/plugin/service/kafka/topic/topic.go — plan-time checks against prior state
• internal/plugin/service/flink/jarversion/jarversion.go — computed checksum that drives replacement

Custom View Overrides

The generator produces standard CRUD views, but you can override any of them via init() when the generated logic is insufficient. Common reasons:

• Create needs extra steps (e.g., reset password after user creation)
• Update touches multiple API operations for different fields
• Delete requires a multi-step state machine (e.g., cancel then delete)
• Read needs post-processing not expressible via modifiers

Use disableView: true on the operation in YAML to skip generating the view you plan to override.

Override pattern:

func init() {
    ResourceOptions.Create = createView   // Custom create
    ResourceOptions.Update = updateView   // Custom update
    ResourceOptions.Delete = deleteView   // Custom delete
}

Example — custom update with multiple API operations (pg_user):

func updateView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error {
    if d.HasChange("pg_allow_replication") {
        req := &service.ServiceUserCredentialsModifyIn{
            Operation: service.ServiceUserCredentialsModifyOperationTypeSetAccessControl,
            AccessControl: &service.AccessControlIn{
                PgAllowReplication: new(d.Get("pg_allow_replication").(bool)),
            },
        }
        _, err := client.ServiceUserCredentialsModify(ctx,
            d.Get("project").(string),
            d.Get("service_name").(string),
            d.Get("username").(string), req)
        if err != nil {
            return err
        }
    }
    return resetPassword(ctx, client, d)
}

Example — custom delete with state machine (flink_application_deployment):

func deleteView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error {
    project := d.Get("project").(string)
    serviceName := d.Get("service_name").(string)
    applicationID := d.Get("application_id").(string)
    deploymentID := d.Get("deployment_id").(string)

    for {
        _, err := client.ServiceFlinkGetApplicationDeployment(ctx, project, serviceName, applicationID, deploymentID)
        if avngen.IsNotFound(err) {
            return nil
        }
        _, err = client.ServiceFlinkCancelApplicationDeployment(ctx, project, serviceName, applicationID, deploymentID)
        if err != nil {
            _, _ = client.ServiceFlinkDeleteApplicationDeployment(ctx, project, serviceName, applicationID, deploymentID)
        }
        select {
        case <-ctx.Done():
            return fmt.Errorf("can't delete: %w", ctx.Err())
        case <-time.After(time.Second):
            continue
        }
    }
}

Reference: See internal/plugin/service/flink/deployment/deployment.go and internal/plugin/service/pg/user/user.go.

Write-Only Fields

Write-only fields are values sent to the API but never stored in Terraform state. Use writeOnly: true in YAML for any field where persisting the value in state is undesirable — passwords, tokens, API keys, configuration payloads, etc.

How it works:

• Write-only fields are automatically excluded from data sources
• ResourceData.Get() reads write-only fields from config (not plan or state, since they're never stored)
• The generator marks them with WriteOnly: true in the Plugin Framework schema

YAML:

schema:
  my_secret:
    type: string
    optional: true
    writeOnly: true
    sensitive: true

Write-Only with Stored Variant

A common pattern offers both a regular field (stored in state) and a write-only variant (not stored), letting users choose. Applicable to passwords, tokens, or any sensitive credential.

YAML:

schema:
  password:
    type: string
    optional: true
    computed: true
    sensitive: true
    conflictsWith: [password_wo]

  password_wo:
    type: string
    optional: true
    writeOnly: true
    sensitive: true
    conflictsWith: [password]
    alsoRequires: [password_wo_version]

  password_wo_version:
    type: integer
    optional: true
    alsoRequires: [password_wo]
    description: Increment to rotate password_wo.

Key points:

• conflictsWith ensures the user picks one approach or the other
• password_wo_version acts as a trigger — incrementing it forces a change even though the write-only value itself isn't tracked in state
• In flattenModifier, clear the regular field from state when the write-only variant is active
• In create/update logic, read the write-only field via d.Get() (falls through to config)

Reference: See internal/plugin/service/pg/user/user.go for a complete implementation.

Data Source with Alternative Lookup Key

When a data source should look up by a field that's NOT in idAttributeComposed (e.g., lookup by name but resource ID uses application_id), add a second read operation marked datasourceLookup: true with resultListLookupKeys. The generator inlines the lookup body into readView as an id-empty branch:

func readView(ctx context.Context, client avngen.Client, d adapter.ResourceData) error {
    // planModifier (if enabled) runs first
    if d.Get("<id-attr>").(string) == "" {
        // ... datasourceLookup list call + FindOne by resultListLookupKeys ...
        return d.Flatten(&match, ...)         // default: flatten match into state and return
        // OR (when resultIDField is set):
        // d.Set("<id-attr>", match.<resultIDField>)  // resolve id, fall through to canonical read
    }
    // ... canonical read API call by id ...
}

The data source uses the same readView directly — no separate dataReadView is generated. The generator also wires ExactlyOneOf(id, alt_field...) (and RequiredTogether when composedOf has more than one field) on the data source config validators, and marks the alternative fields as optional in the data source schema.

YAML:

clientHandler: flinkapplication
idAttributeComposed: [project, service_name, application_id]
rename:
  id: application_id
operations:
  - id: ServiceFlinkCreateApplication
    type: create
  - id: ServiceFlinkGetApplication
    type: read
  - id: ServiceFlinkListApplications
    type: read
    datasourceLookup: true
    resultKey: applications        # Unwrap the response: rsp.applications -> []Application
    resultListLookupKeys:
      Name: name                   # API field "Name" matches TF attribute "name"
  - id: ServiceFlinkDeleteApplication
    type: delete
  - id: ServiceFlinkUpdateApplication
    type: update

The rename map (e.g. id: application_id) is forwarded to the lookup branch's Flatten call when the API field exists in the lookup response, so the resource id attribute is populated correctly from the list item.

Multi-field composite lookup: if resultListLookupKeys declares more than one mapping, the data source requires either the id attribute OR all alternative fields together. Example (aiven_kafka_schema_registry_acl):

resultListLookupKeys:
  Permission: permission
  Resource: resource
  Username: username

resultIDField — id resolution only

Set resultIDField to the Go field name on the lookup result item that holds the primary id when the lookup endpoint and the canonical read endpoint return different shapes (the list response is just a directory of ids; the actual payload comes from the canonical read). With resultIDField set, readView's id-empty branch:

1. Calls the datasourceLookup list op.
2. Finds the matching item by resultListLookupKeys.
3. Sets the resolved id on state via d.Set(<id-attr>, match.<resultIDField>).
4. Falls through to the canonical read body in the same readView (no recursive call).

The lookup response is not merged into the data source schema, so leaked fields from the directory endpoint cannot pollute it.

resultIDField requires datasourceLookup: true and resultListLookupKeys (enforced by .schema.yml dependencies).

operations:
  - id: OrganizationUserList         # canonical read, fetches the actual payload
    type: read
    resultToKey: users
  - id: UserOrganizationsList        # directory used only to resolve the id
    type: read
    datasourceLookup: true
    resultIDField: OrganizationId    # Go field on the list item holding the id
    resultKey: organizations
    resultListLookupKeys:
      OrganizationName: name
rename:
  organization_id: id

No planModifier needed: both patterns fully replace the previous datasource.exactlyOneOf + custom planModifier approach.

Reference implementations:

• definitions/aiven_flink_application.yml — single-field name lookup (flatten match into state)
• definitions/aiven_kafka_schema_registry_acl.yml — three-field composite lookup
• definitions/aiven_organizational_unit.yml — name lookup with field renames
• definitions/aiven_organization_user_list.yml — resultIDField, lookup resolves id then falls through to the canonical read body

Computed + Optional Pattern

Use computed: true + optional: true when the API always returns a value for a field, even when not configured. Without computed, you'll get:

Error: Provider produced inconsistent result after apply
.field_name: was null, but now cty.False

Solution:

schema:
  field_name:
    type: boolean
    optional: true
    computed: true
    useStateForUnknown: true  # Preserves prior state during planning

Trade-off: Users who didn't configure the field will see a one-time cosmetic diff on upgrade (null -> false), but no resource recreation.

Common Resource Patterns

Search the codebase for similar patterns:

Pattern	Search Command
Data source (list)	grep -l "datasource:" definitions/aiven_*.yml | xargs grep -l "resultToKey"
Composite ID	grep -l "idAttributeComposed:" definitions/aiven_*.yml | head -3
Custom modifiers	grep -l "expandModifier: true" definitions/aiven_*.yml
Field renaming	grep -l "rename:" definitions/aiven_*.yml
Alt data source lookup key	grep -l "datasourceLookup: true" definitions/aiven_*.yml

Best approach: Find a similar resource, read its YAML definition, understand the pattern, adapt to your needs.

Troubleshooting

Error	Solution
operationID X not found	Search OpenAPI: jq '.paths | to_entries[] | .value | to_entries[] | .value.operationId' openapi.json | grep -i X
no 'id' field found	Add idAttributeComposed: [field1, field2] to YAML
ID field "X" not found	Verify field exists in API response, check rename mappings
Generation fails	Run task get-spec, validate YAML syntax, check operation IDs
Infinite plan changes	Use arrayOrdered not array, ensure idAttributeComposed fields are stable
"was null, but now cty.X"	Add computed: true + useStateForUnknown: true to field

Reference Implementations

Resource	Patterns Demonstrated
pg_user	Nested API fields, computed+optional, custom create/update, write-only fields, expand/flatten modifiers
mysql_database	Simple CRUD, list-based read with lookup, termination protection
billing_group	planModifier, ComposeMapModifiers, card ID resolution, organization ID conversion
flink_application	Alt data source lookup key via datasourceLookup read op, field rename
flink_application_deployment	Renamed ID field, planModifier for backward compat, custom delete with state machine
kafka_schema_registry_acl	Composite alt data source lookup (multi-field datasourceLookup + resultListLookupKeys)
organization/unit	Alt data source lookup via datasourceLookup read op, expand/flatten for parent ID
flink/jarversion	Attributes the API doesn't have, modifyPlan computing a checksum that drives replacement, RefreshStateCheck, custom create that uploads a file

Testing Requirements

CRITICAL: Every generated resource MUST have acceptance tests covering:

For Resources

1. Create - Basic resource creation
2. Read - Verify attributes are read correctly
3. Update - Modify attributes, verify changes
4. Delete - Implicit in test cleanup
5. Import - Test terraform import with correct ID format

Example test structure:

func TestAccAivenMyResource_basic(t *testing.T) {
    resource.ParallelTest(t, resource.TestCase{
        PreCheck:                 func() { acc.TestAccPreCheck(t) },
        ProtoV6ProviderFactories: acc.TestProtoV6ProviderFactories,
        Steps: []resource.TestStep{
            {
                Config: testAccMyResourceConfig("value1"),
                Check:  resource.TestCheckResourceAttr(resourceName, "field", "value1"),
            },
            {
                Config: testAccMyResourceConfig("value2"),
                Check:  resource.TestCheckResourceAttr(resourceName, "field", "value2"),
            },
            {
                ResourceName:      resourceName,
                ImportState:       true,
                ImportStateVerify: true,
            },
        },
    })
}

Find test examples: ls internal/plugin/service/*/mysql/*_test.go

Commands

task get-spec                          # Update OpenAPI spec
task generate                          # Generate code
task generate no_spec=true             # Generate without spec update
task build                             # Build provider
task lint                              # Run linters
task test-unit                         # Unit tests (no API)
task test-acc -- -run TestName         # Specific acceptance test

Key Principles

1. Learn from existing code - Always find and read similar resources in definitions/
2. Start minimal - Basic YAML first, add complexity incrementally
3. Use arrayOrdered - For complex/large nested objects, always use arrayOrdered (list) not array (set) for performance
4. Mark sensitive fields - Use sensitive: true for passwords, tokens, API keys, credentials
5. Follow conventions - Match patterns from existing resources (naming, structure, etc.)
6. Don't edit zz_* files - These are generated. Custom logic goes in separate .go files

Important Notes

• New resources go in internal/plugin/ (Plugin Framework), NOT internal/sdkprovider/ (legacy)
• Generated files have zz_ prefix - never edit them manually
• Custom logic goes in separate .go files in the same package (e.g., billinggroup.go)
• Run task lint before committing
• Definition files MUST have aiven_ prefix: definitions/aiven_my_resource.yml -> resource aiven_my_resource
• Files without aiven_ prefix in definitions/ are ignored by the generator

Migrating Existing Resources

If you need to migrate an existing SDK resource from internal/sdkprovider/ to Plugin Framework, use the tf-resource-migration skill instead. That skill covers:

• Analyzing existing SDK code
• SDK type -> YAML type mapping
• Preserving state compatibility
• Backward compatibility testing
• Deprecation strategy