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Naming Conventions for the AWS Provider

Service Identifier

In the AWS Provider, a service identifier should consistently identify an AWS service from code to documentation to provider used by a practitioner. Prominent places you will see service identifiers:

  • The package name (e.g., internal/service/<serviceidentifier>)
  • In resource and data source names (e.g., aws_<serviceidentifier>_thing)
  • Documentation file names (e.g., website/docs/r/<serviceidentifier>_thing)

Typically, choosing the AWS Provider identifier for a service is simple. AWS consistently uses one name and we use that name as the identifier. However, some services are not simple. To provide consistency, and to help contributors and practitioners know what to expect, we provide this rule for defining a service identifier:

Rule

  1. Determine the service package name for AWS Go SDK v2.
  2. Determine the AWS CLI v2 command corresponding to the service (i.e., the word following aws in CLI commands; e.g., for aws sts get-caller-identity, sts is the command, get-caller-identity is the subcommand).
  3. If the SDK and CLI agree, use that. If the service only exists in one, use that.
  4. If they differ, use the shorter of the two.
  5. Use lowercase letters and do not include any underscores (_).

How Well Is It Followed?

With 156+ services having some level of implementation, the following is a summary of how well this rule is currently followed.

For AWS provider service package names, only five packages violate this rule: appautoscaling should be applicationautoscaling, codedeploy should be deploy, elasticsearch should be es, cloudwatchlogs should be logs, and simpledb should be sdb.

For the service identifiers used in resource and data source configuration names (e.g., aws_acmpca_certificate_authority), 32 wholly or partially violate the rule.

  • EC2, ELB, ELBv2, and RDS have legacy but heavily used resources and data sources that do not or inconsistently use service identifiers.
  • The remaining 28 services violate the rule in a consistent way: appautoscaling should be applicationautoscaling, codedeploy should be deploy, elasticsearch should be es, cloudwatch_log should be logs, simpledb should be sdb, prometheus should be amp, api_gateway should be apigateway, cloudcontrolapi should be cloudcontrol, cognito_identity should be cognitoidentity, cognito should be cognitoidp, config should be configservice, dx should be directconnect, directory_service should be ds, elastic_beanstalk should be elasticbeanstalk, cloudwatch_event should be events, kinesis_firehose should be firehose, msk should be kafka, mskconnect should be kafkaconnect, kinesis_analytics should be kinesisanalytics, kinesis_video should be kinesisvideo, lex should be lexmodels, media_convert should be mediaconvert, media_package should be mediapackage, media_store should be mediastore, route53_resolver should be route53resolver, relevant s3 should be s3control, serverlessapplicationrepository should be serverlessrepo, and service_discovery should be servicediscovery.

Packages

Package names are not seen or used by practitioners. However, they should still be carefully considered.

Rule

  1. For service packages (i.e., packages under internal/service), use the AWS Provider service identifier as the package name.
  2. For other packages, use a short name for the package. Common Go lengths are 3-9 characters.
  3. Use a descriptive name. The name should capture the key purpose of the package.
  4. Use lowercase letters and do not include any underscores (_).
  5. Avoid useless names like helper. These names convey zero information. Everything in the AWS Provider is helping something or someone do something so the name helper doesn't narrow down the purpose of the package within the codebase.
  6. Use a name that is not too narrow or too broad as Go packages should not be too big or too small. Tiny packages can be combined using a broader name encompassing both. For example, verify is a good name because it tells you what the package does and allows a broad set of validation, comparison, and checking functionality.

Resources and Data Sources

When creating a new resource or data source, it is important to get names right. Once practitioners rely on names, we can only change them through breaking changes. If you are unsure about what to call a resource or data source, discuss it with the community and maintainers.

Rule

  1. Follow the AWS SDK for Go v2. Almost always, the API operations make determining the name simple. For example, the Amazon CloudWatch Evidently service includes CreateExperiment, GetExperiment, UpdateExperiment, and DeleteExperiment. Thus, the resource (or data source) name is "Experiment."
  2. Give a resource its Terraform configuration (i.e., HCL) name (e.g., aws_imagebuilder_image_pipeline) by joining these three parts with underscores:
    • aws prefix
    • Service identifier (service identifiers do not include underscores), all lowercase (e.g., imagebuilder)
    • Resource (or data source) name in snake case (spaces replaced with underscores, if any), all lowercase (e.g., image_pipeline)
  3. Name the main resource function Resource<ResourceName>(), with the resource name in Mixed Caps. Do not include the service name or identifier. For example, define ResourceImagePipeline() in a file called internal/service/imagebuilder/image_pipeline.go.
  4. Similarly, name the main data source function DataSource<ResourceName>(), with the data source name in Mixed Caps. Do not include the service name or identifier. For example, define DataSourceImagePipeline() in a file called internal/service/imagebuilder/image_pipeline_data_source.go.

Files

File names should follow Go and Markdown conventions with these additional points.

Resource and Data Source Documentation Rule

  1. Resource markdown goes in the website/docs/r directory. Data source markdown goes in the website/docs/d directory.
  2. Use the service identifier and resource or data source name, separated by an underscore (_).
  3. All letters are lowercase.
  4. Use .html.markdown as the extension.
  5. Do not include "aws" in the name.

A correct example is accessanalyzer_analyzer.html.markdown. An incorrect example is service_discovery_instance.html.markdown because the service identifier should not include an underscore.

Go File Rule

  1. Resource and data source files are in the internal/service/<service> directory.
  2. Do not include the service as part of the file name.
  3. Data sources should include _data_source after the data source name (e.g., application_data_source.go).
  4. Put unit and acceptance tests in a file ending with _test.go (e.g., custom_domain_association_test.go).
  5. Use snake case for multiword names (i.e., all letters are lowercase, words separated by underscores).
  6. Use the .go extension.
  7. Idiomatic names for common non-resource, non-data-source files include consts.go (service-wide constants), find.go (finders), flex.go (FLatteners and EXpanders), generate.go (directives for code generation), id.go (ID creators and parsers), status.go (status functions), sweep.go (sweepers), tags_gen.go (generated tag code), validate.go (validators), and wait.go (waiters).

Mixed Caps

!!! note Mixed Caps is different than camel case, Pascal case, or snake case!

Idiomatic Go uses Mixed Caps for multiword names in code. Mixed caps is similar to camel case except initialisms and abbreviations in mixed caps should be the correct, human-readable case, such as VPCEndpoint not VpcEndpoint. After all, names in code are for humans.

An acronym such as "VPC" should either be all capitalized ("VPC") or all lowercase ("vpc"), never "Vpc" or "vPC." Similarly, in mixedCaps, "DynamoDB" should either be "DynamoDB" or "dynamoDB", depending on whether an initial cap is needed or not, and never "dynamoDb" or "DynamoDb."

For more details on capitalizations we enforce with CI Semgrep tests, see the Caps List.

Rule

  1. Use mixedCaps for names (such as for functions, types, methods, variables, and constants) in the Terraform AWS Provider Go code.

Functions

In general, follow Go best practices for good function naming. This rule is for functions defined outside of the test context (i.e., not in a file ending with _test.go). For test functions, see Test Support Functions or Acceptance Test Configurations below.

Rule

  1. Only export functions (capitalize) when necessary, i.e., when the function is used outside the current package, including in the _test (.test) package.
  2. Use MixedCaps (exported) or mixedCaps (not exported). Do not use underscores for multiwords.
  3. Do not include the service name in the function name. (If functions are used outside the current package, the import package clarifies a function's origin. For example, the EC2 function FindVPCEndpointByID() is used outside the internal/service/ec2 package but where it is used, the call is tfec2.FindVPCEndpointByID().)
  4. For CRUD functions for resources, use this format: resource<ResourceName><CRUDFunction>. For example, resourceImageRecipeUpdate(), resourceBaiduChannelRead().
  5. For data sources, for Read functions, use this format: dataSource<DataSourceName>Read. For example, dataSourceBrokerRead(), dataSourceEngineVersionRead().
  6. To improve readability, consider including the resource name in helper function names that pertain only to that resource. For example, for an expander function for an "App" resource and a "Campaign Hook" expander, use expandAppCampaignHook().
  7. Do not include "AWS" or "Aws" in the name.

Variables and Constants

In general, follow Go best practices for good variable and constant naming.

Rule

  1. Only export variables and constants (capitalize) when necessary, i.e., the variable or constant is used outside the current package, including in the _test (.test) package.
  2. Use MixedCaps (exported) or mixedCaps (not exported). Do not use underscores for multiwords.
  3. Do not include the service name in variable or constant names. (If variables or constants are used outside the current package, the import package clarifies its origin. For example, IAM's PropagationTimeout is widely used outside of IAM but each instance is through the package import alias, tfiam.PropagationTimeout. "IAM" is unnecessary in the constant name.)
  4. To improve readability, consider including the resource name in variable and constant names that pertain only to that resource. For example, for a string constant for a "Role" resource and a "not found" status, use roleStatusNotFound or RoleStatusNotFound, if used outside the service's package.
  5. Do not include "AWS" or "Aws" in the name.

!!! note Give priority to constants from the AWS SDK for Go rather than defining new constants for the same values.

Acceptance and Unit Tests

With about 6000 acceptance and unit tests, following these naming conventions is essential to organization and (human) context switching between services.

There are three types of tests in the AWS Provider: (regular) acceptance tests, serialized acceptance tests, and unit tests. All are functions that take a variable of type *testing.T. Acceptance tests and unit tests have exported (i.e., capitalized) names while serialized tests do not. Serialized tests are called by another exported acceptance test, often ending with _serial. The majority of tests in the AWS provider are acceptance tests.

Acceptance Test Rule

Acceptance test names have a minimum of two (e.g., TestAccBackupPlan_tags) or a maximum of three (e.g., TestAccDynamoDBTable_Replica_multiple) parts, joined with underscores:

  1. First part: All have a prefix (i.e., TestAcc), service name (e.g., Backup, DynamoDB), and resource name (e.g., Plan, Table), Mixed Caps without underscores between. Do not include "AWS" or "Aws" in the name.
  2. Middle part (Optional): Test group (e.g., Replica), uppercase, Mixed Caps. Consider a metaphor where tests are chapters in a book. If it is helpful, tests can be grouped together like chapters in a book that are sometimes grouped into parts or sections of the book.
  3. Last part: Test identifier (e.g., basic, tags, or multiple), lowercase, mixedCaps). The identifier should make the test's purpose clear but be concise. For example, the identifier conflictsWithCloudFrontDefaultCertificate (41 characters) conveys no more information than conflictDefaultCertificate (26 characters), since "CloudFront" is implied and "with" is always implicit. Avoid words that convey no meaning or whose meaning is implied. For example, "with" (e.g., _withTags) is not needed because we imply the name is telling us what the test is with. withTags can be simplified to tags.

Serialized Acceptance Test Rule

The names of serialized acceptance tests follow the regular acceptance test name rule except for serialized acceptance test names:

  1. Start with testAcc instead of TestAcc
  2. Do not include the name of the service (e.g., a serialized acceptance test would be called testAccApp_basic not testAccAmplifyApp_basic).

Unit Test Rule

Unit test names follow the same rule as acceptance test names except for unit test names:

  1. Start with Test, not TestAcc
  2. Do not include the name of the service
  3. Usually do not have any underscores
  4. If they test a function, should include the function name (e.g., a unit test of ExpandListener() should be called TestExpandListener())

Test Support Functions

This rule is for functions defined in the test context (i.e., in a file ending with _test.go) that do not return a string with Terraform configuration. For non-test functions, see Functions above. Or, see Acceptance Test Configurations below.

Rule

  1. Only export functions (capitalize) when necessary, i.e., when the function is used outside the current package. This is very rare.
  2. Use MixedCaps (exported) or mixedCaps (not exported). Do not use underscores for multiwords.
  3. Do not include the service name in the function name. For example, testAccCheckAMPWorkspaceExists() should be named testAccCheckWorkspaceExists() instead, dropping the service name.
  4. Several types of support functions occur commonly and should follow these patterns:
    • Destroy: testAccCheck<Resource>Destroy
    • Disappears: testAccCheck<Resource>Disappears
    • Exists: testAccCheck<Resource>Exists
    • Not Recreated: testAccCheck<Resource>NotRecreated
    • PreCheck: testAccPreCheck (often, only one PreCheck is needed per service so no resource name is needed)
    • Recreated: testAccCheck<Resource>Recreated
  5. Do not include "AWS" or "Aws" in the name.

Acceptance Test Configurations

This rule is for functions defined in the test context (i.e., in a file ending with _test.go) that return a string with Terraform configuration. For test support functions, see Test Support Functions above. Or, for non-test functions, see Functions above.

!!! note This rule is not widely used currently. However, new functions and functions you change should follow it.

Rule

  1. Only export functions (capitalize) when necessary, i.e., when the function is used outside the current package. This is very rare.
  2. Use MixedCaps (exported) or mixedCaps (not exported). Do not use underscores for multiwords.
  3. Do not include the service name in the function name.
  4. Follow this pattern: testAccConfig<Resource>_<TestGroup>_<configDescription>
    • _<TestGroup> is optional. Refer to the Acceptance Test Rule test group discussion.
    • Especially when an acceptance test only uses one configuration, the <configDescription> should be the same as the test identifier discussed in the Acceptance Test Rule.
  5. Do not include "AWS" or "Aws" in the name.