Do not set RUSTFLAGS environment variable when invoking Cargo commands via Gradle tasks

Otherwise, if you generate a crate and compile it using Gradle, like for
example using the invocation:

```
./gradlew -P modules='simple' -P cargoCommands='test' codegen-server-test:build
```

And then manually run a `cargo` command within the generated crate
directory, or open the project using `rust-analyzer`, Cargo will
re-compile the project from scratch, with
`CARGO_LOG=cargo::core::compiler::fingerprint=trace` reporting that
flags have changed since the last compilation.

Instead, it's best if we persist these flags to `.cargo/config.toml`, so
all `cargo` invocations, either through Gradle, manually, or through
`rust-analyzer`, use the same set. This way, if no files were changed,
subsequent compilations since code generation will truly be no-ops, with
Cargo reusing all artifacts.

Note this commit fixes a regression that was introduced when `--cfg
aws_sdk_unstable` was introduced in #2614, since I fixed this the first
time back in #1422.

Author: david-perez

Diff for: aws/sdk-adhoc-test/build.gradle.kts

@@ -20,7 +20,6 @@ java {
 }
 
 val smithyVersion: String by project
-val defaultRustDocFlags: String by project
 val properties = PropertyRetriever(rootProject, project)
 
 val pluginName = "rust-client-codegen"
@@ -78,7 +77,7 @@ tasks["smithyBuild"].dependsOn("generateSmithyBuild")
 tasks["assemble"].finalizedBy("generateCargoWorkspace")
 
 project.registerModifyMtimeTask()
-project.registerCargoCommandsTasks(layout.buildDirectory.dir(workingDirUnderBuildDir).get().asFile, defaultRustDocFlags)
+project.registerCargoCommandsTasks(layout.buildDirectory.dir(workingDirUnderBuildDir).get().asFile)
 
 tasks["test"].finalizedBy(cargoCommands(properties).map { it.toString })
 

Diff for: aws/sdk/build.gradle.kts

@@ -31,7 +31,6 @@ configure<software.amazon.smithy.gradle.SmithyExtension> {
 }
 
 val smithyVersion: String by project
-val defaultRustDocFlags: String by project
 val properties = PropertyRetriever(rootProject, project)
 
 val crateHasherToolPath = rootProject.projectDir.resolve("tools/ci-build/crate-hasher")
@@ -442,7 +441,7 @@ tasks["assemble"].apply {
     outputs.upToDateWhen { false }
 }
 
-project.registerCargoCommandsTasks(outputDir.asFile, defaultRustDocFlags)
+project.registerCargoCommandsTasks(outputDir.asFile)
 project.registerGenerateCargoConfigTomlTask(outputDir.asFile)
 
 //The task name "test" is already registered by one of our plugins

Diff for: buildSrc/src/main/kotlin/CodegenTestCommon.kt

@@ -248,13 +248,15 @@ fun Project.registerGenerateCargoWorkspaceTask(
 fun Project.registerGenerateCargoConfigTomlTask(outputDir: File) {
     this.tasks.register("generateCargoConfigToml") {
         description = "generate `.cargo/config.toml`"
+        // TODO(https://github.com/smithy-lang/smithy-rs/issues/1068): Once doc normalization
+        // is completed, warnings can be prohibited in rustdoc by setting `rustdocflags` to `-D warnings`.
         doFirst {
             outputDir.resolve(".cargo").mkdirs()
             outputDir.resolve(".cargo/config.toml")
                 .writeText(
                     """
                     [build]
-                    rustflags = ["--deny", "warnings"]
+                    rustflags = ["--deny", "warnings", "--cfg", "aws_sdk_unstable"]
                     """.trimIndent(),
                 )
         }
@@ -298,10 +300,7 @@ fun Project.registerModifyMtimeTask() {
     }
 }
 
-fun Project.registerCargoCommandsTasks(
-    outputDir: File,
-    defaultRustDocFlags: String,
-) {
+fun Project.registerCargoCommandsTasks(outputDir: File) {
     val dependentTasks =
         listOfNotNull(
             "assemble",
@@ -312,29 +311,24 @@ fun Project.registerCargoCommandsTasks(
     this.tasks.register<Exec>(Cargo.CHECK.toString) {
         dependsOn(dependentTasks)
         workingDir(outputDir)
-        environment("RUSTFLAGS", "--cfg aws_sdk_unstable")
         commandLine("cargo", "check", "--lib", "--tests", "--benches", "--all-features")
     }
 
     this.tasks.register<Exec>(Cargo.TEST.toString) {
         dependsOn(dependentTasks)
         workingDir(outputDir)
-        environment("RUSTFLAGS", "--cfg aws_sdk_unstable")
         commandLine("cargo", "test", "--all-features", "--no-fail-fast")
     }
 
     this.tasks.register<Exec>(Cargo.DOCS.toString) {
         dependsOn(dependentTasks)
         workingDir(outputDir)
-        environment("RUSTDOCFLAGS", defaultRustDocFlags)
-        environment("RUSTFLAGS", "--cfg aws_sdk_unstable")
         commandLine("cargo", "doc", "--no-deps", "--document-private-items")
     }
 
     this.tasks.register<Exec>(Cargo.CLIPPY.toString) {
         dependsOn(dependentTasks)
         workingDir(outputDir)
-        environment("RUSTFLAGS", "--cfg aws_sdk_unstable")
         commandLine("cargo", "clippy")
     }
 }

Diff for: codegen-client-test/build.gradle.kts

@@ -15,7 +15,6 @@ plugins {
 }
 
 val smithyVersion: String by project
-val defaultRustDocFlags: String by project
 val properties = PropertyRetriever(rootProject, project)
 fun getSmithyRuntimeMode(): String = properties.get("smithy.runtime.mode") ?: "orchestrator"
 
@@ -130,7 +129,7 @@ tasks["smithyBuild"].dependsOn("generateSmithyBuild")
 tasks["assemble"].finalizedBy("generateCargoWorkspace")
 
 project.registerModifyMtimeTask()
-project.registerCargoCommandsTasks(layout.buildDirectory.dir(workingDirUnderBuildDir).get().asFile, defaultRustDocFlags)
+project.registerCargoCommandsTasks(layout.buildDirectory.dir(workingDirUnderBuildDir).get().asFile)
 
 tasks["test"].finalizedBy(cargoCommands(properties).map { it.toString })
 

Diff for: codegen-server-test/build.gradle.kts

@@ -16,7 +16,6 @@ plugins {
 }
 
 val smithyVersion: String by project
-val defaultRustDocFlags: String by project
 val properties = PropertyRetriever(rootProject, project)
 
 val pluginName = "rust-server-codegen"
@@ -117,7 +116,7 @@ tasks["smithyBuild"].dependsOn("generateSmithyBuild")
 tasks["assemble"].finalizedBy("generateCargoWorkspace", "generateCargoConfigToml")
 
 project.registerModifyMtimeTask()
-project.registerCargoCommandsTasks(layout.buildDirectory.dir(workingDirUnderBuildDir).get().asFile, defaultRustDocFlags)
+project.registerCargoCommandsTasks(layout.buildDirectory.dir(workingDirUnderBuildDir).get().asFile)
 
 tasks["test"].finalizedBy(cargoCommands(properties).map { it.toString })
 

Diff for: codegen-server-test/python/build.gradle.kts

@@ -16,7 +16,6 @@ plugins {
 }
 
 val smithyVersion: String by project
-val defaultRustDocFlags: String by project
 val properties = PropertyRetriever(rootProject, project)
 val buildDir = layout.buildDirectory.get().asFile
 
@@ -120,7 +119,7 @@ tasks["smithyBuild"].dependsOn("generateSmithyBuild")
 tasks["assemble"].finalizedBy("generateCargoWorkspace")
 
 project.registerModifyMtimeTask()
-project.registerCargoCommandsTasks(buildDir.resolve(workingDirUnderBuildDir), defaultRustDocFlags)
+project.registerCargoCommandsTasks(buildDir.resolve(workingDirUnderBuildDir))
 
 tasks["test"].finalizedBy(cargoCommands(properties).map { it.toString })
 

Diff for: codegen-server-test/typescript/build.gradle.kts

@@ -16,7 +16,6 @@ plugins {
 }
 
 val smithyVersion: String by project
-val defaultRustDocFlags: String by project
 val properties = PropertyRetriever(rootProject, project)
 val buildDir = layout.buildDirectory.get().asFile
 
@@ -49,7 +48,7 @@ tasks["smithyBuild"].dependsOn("generateSmithyBuild")
 tasks["assemble"].finalizedBy("generateCargoWorkspace")
 
 project.registerModifyMtimeTask()
-project.registerCargoCommandsTasks(buildDir.resolve(workingDirUnderBuildDir), defaultRustDocFlags)
+project.registerCargoCommandsTasks(buildDir.resolve(workingDirUnderBuildDir))
 
 tasks["test"].finalizedBy(cargoCommands(properties).map { it.toString })
 

Diff for: gradle.properties

@@ -31,10 +31,4 @@ kotlinVersion=1.9.20
 ktlintVersion=1.0.1
 kotestVersion=5.8.0
 # Avoid registering dependencies/plugins/tasks that are only used for testing purposes
-isTestingEnabled=true
-
-# TODO(https://github.com/smithy-lang/smithy-rs/issues/1068): Once doc normalization
-# is completed, warnings can be prohibited in rustdoc.
-#
-# defaultRustDocFlags=-D warnings
-defaultRustDocFlags=
+isTestingEnabled=true