Add terraform.imports and terraform.checks functions (#69)

* Add `terraform.imports` function

* Add `terraform.checks` function

Author: wata727

docs/functions.md

@@ -566,6 +566,111 @@ terraform.moved_blocks({"from": "any"}, {})
 ]
 ```
 
+## `terraform.imports`
+
+```rego
+blocks := terraform.imports(schema, options)
+```
+
+Returns Terraform imports blocks.
+
+- `schema` (schema): schema for attributes referenced in rules.
+- `options` (object[string: string]): options to change the retrieve/evaluate behavior.
+
+Returns:
+
+- `blocks` (array[object<config: body, decl_range: range>]): Terraform "import" blocks.
+
+The `schema` and `options` are equivalent to the arguments of the `terraform.resources` function.
+
+Examples:
+
+```hcl
+import {
+  to = aws_instance.example
+  id = "i-abcd1234"
+}
+```
+
+```rego
+terraform.imports({"id": "string"}, {})
+```
+
+```json
+[
+  {
+    "config": {
+      "id": {
+        "value": "i-abcd1234",
+        "unknown": false,
+        "sensitive": false,
+        "range": {...}
+      }
+    },
+    "decl_range": {...}
+  }
+]
+```
+
+## `terraform.checks`
+
+```rego
+blocks := terraform.checks(schema, options)
+```
+
+Returns Terraform check blocks.
+
+- `schema` (schema): schema for attributes referenced in rules.
+- `options` (object[string: string]): options to change the retrieve/evaluate behavior.
+
+Returns:
+
+- `blocks` (array[object<config: body, decl_range: range>]): Terraform "check" blocks.
+
+The `schema` and `options` are equivalent to the arguments of the `terraform.resources` function.
+
+Examples:
+
+```hcl
+check "health_check" {
+  data "http" "terraform_io" {
+    url = "https://www.terraform.io"
+  }
+
+  assert {
+    condition = data.http.terraform_io.status_code == 200
+    error_message = "${data.http.terraform_io.url} returned an unhealthy status code"
+  }
+}
+```
+
+```rego
+terraform.checks({"assert": {"condition": "bool"}}, {})
+```
+
+```json
+[
+  {
+    "config": {
+      "assert": [
+        {
+          "config": {
+            "condition": {
+              "unknown": true,
+              "sensitive": false,
+              "range": {...}
+            }
+          },
+          "labels": null,
+          "decl_range": {...}
+        }
+      ]
+    },
+    "decl_range": {...}
+  }
+]
+```
+
 ## `terraform.module_range`
 
 ```rego

integration/checks/.tflint.hcl

@@ -0,0 +1,9 @@
+plugin "terraform" {
+  enabled = false
+}
+
+plugin "opa" {
+  enabled = true
+
+  policy_dir = "policies"
+}

integration/checks/main.tf

@@ -0,0 +1,17 @@
+check "health_check" {
+  data "http" "terraform_io" {
+    url = "https://www.terraform.io"
+  }
+
+  assert {
+    condition = data.http.terraform_io.status_code == 200
+    error_message = "${data.http.terraform_io.url} returned an unhealthy status code"
+  }
+}
+
+check "deterministic" {
+  assert {
+    condition = 200 == 200
+    error_message = "condition should be true"
+  }
+}

integration/checks/policies/main.rego

@@ -0,0 +1,9 @@
+package tflint
+
+deny_deterministic_check_condition[issue] {
+  checks := terraform.checks({"assert": {"condition": "bool"}}, {})
+  condition = checks[_].config.assert[_].config.condition
+  condition.unknown == false
+
+  issue := tflint.issue("deterministic check condtion is not allowed", condition.range)
+}

integration/checks/policies/main_test.rego

@@ -0,0 +1,24 @@
+package tflint
+import future.keywords
+
+mock_checks(schema, options) := terraform.mock_checks(schema, options, {"main.tf": `
+check "deterministic" {
+  assert {
+    condition = 200 == 200
+    error_message = "condition should be true"
+  }
+}`})
+
+test_deny_deterministic_check_condition_passed if {
+  issues := deny_deterministic_check_condition with terraform.checks as mock_checks
+
+  count(issues) == 1
+  issue := issues[_]
+  issue.msg == "deterministic check condtion is not allowed"
+}
+
+test_deny_deterministic_check_condition_failed if {
+  issues := deny_deterministic_check_condition with terraform.checks as mock_checks
+
+  count(issues) == 0
+}

integration/checks/result.json

@@ -0,0 +1,25 @@
+{
+  "issues": [
+    {
+      "rule": {
+        "name": "opa_deny_deterministic_check_condition",
+        "severity": "error",
+        "link": "policies/main.rego:3"
+      },
+      "message": "deterministic check condtion is not allowed",
+      "range": {
+        "filename": "main.tf",
+        "start": {
+          "line": 14,
+          "column": 17
+        },
+        "end": {
+          "line": 14,
+          "column": 27
+        }
+      },
+      "callers": []
+    }
+  ],
+  "errors": []
+}

integration/checks/result_test.json

@@ -0,0 +1,25 @@
+{
+  "issues": [
+    {
+      "rule": {
+        "name": "opa_test_deny_deterministic_check_condition_failed",
+        "severity": "error",
+        "link": "policies/main_test.rego:20"
+      },
+      "message": "test failed",
+      "range": {
+        "filename": "",
+        "start": {
+          "line": 0,
+          "column": 0
+        },
+        "end": {
+          "line": 0,
+          "column": 0
+        }
+      },
+      "callers": []
+    }
+  ],
+  "errors": []
+}

integration/imports/.tflint.hcl

@@ -0,0 +1,9 @@
+plugin "terraform" {
+  enabled = false
+}
+
+plugin "opa" {
+  enabled = true
+
+  policy_dir = "policies"
+}

integration/imports/main.tf

@@ -0,0 +1,4 @@
+import {
+  to = aws_instance.example
+  id = "i-abcd1234"
+}

integration/imports/policies/main.rego

@@ -0,0 +1,8 @@
+package tflint
+
+deny_import_blocks[issue] {
+  imports := terraform.imports({}, {})
+  count(imports) > 0
+
+  issue := tflint.issue("import blocks are not allowed", imports[0].decl_range)
+}