[WIP] compile-tab: add evmVersion

Specifying a specific EVM version for `solc` to target
is useful when targetting older private chains deployments
with the latest compiler.

This work in progress patch adds an "EVM Version" drop down menu
in the compiler tab.

This patch depends on https://github.com/ethereum/remix/pull/1193
in `remix-solidity` to pass down the `evmVersion` option.

src/app/tabs/compileTab/compileTab.js

@@ -25,6 +25,13 @@ class CompileTab {
     this.optimize = this.optimize === 'true'
     this.queryParams.update({ optimize: this.optimize })
     this.compiler.setOptimize(this.optimize)
+
+    this.evmVersion = this.queryParams.get().evmVersion
+    if (this.evmVersion === 'undefined' || this.evmVersion === 'null' || !this.evmVersion) {
+      this.evmVersion = null
+    }
+    this.queryParams.update({ evmVersion: this.evmVersion })
+    this.compiler.setEvmVersion(this.evmVersion)
   }
 
   setOptimize (newOptimizeValue) {
@@ -33,6 +40,12 @@ class CompileTab {
     this.compiler.setOptimize(this.optimize)
   }
 
+  setEvmVersion (newEvmVersion) {
+    this.evmVersion = newEvmVersion
+    this.queryParams.update({ evmVersion: this.evmVersion })
+    this.compiler.setEvmVersion(this.evmVersion)
+  }
+
   /**
    * Compile a specific file of the file manager
    * @param {string} target the path to the file to compile

src/app/tabs/compileTab/compilerContainer.js

@@ -134,6 +134,33 @@ class CompilerContainer {
       </select>`
     this._view.version = yo`<span id="version"></span>`
 
+    this._view.evmVersionSelector = yo`
+      <select onchange="${this.onchangeEvmVersion.bind(this)}" class="custom-select" id="evmVersionSelector">
+        <option disabled selected>EVM Version: default</option>
+        <option value="default">compiler default</option>
+        <option>petersburg</option>
+        <option>constantinople</option>
+        <option>byzantium</option>
+        <option>spuriousDragon</option>
+        <option>tangerineWhistle</option>
+        <option>homestead</option>
+      </select>`
+    if (this.compileTabLogic.evmVersion) {
+      let s = this._view.evmVersionSelector
+      let i
+      for (i = 0; i < s.options.length; i++) {
+        if (s.options[i].value === this.compileTabLogic.evmVersion) {
+          break
+        }
+      }
+      if (i === s.options.length) { // invalid evmVersion from queryParams
+        s.selectedIndex = 1 // compiler default
+        this.onchangeEvmVersion()
+      } else {
+        s.selectedIndex = i
+      }
+    }
+
     this._view.compilationButton = this.compilationButton()
 
     this._view.compileContainer = yo`
@@ -145,6 +172,9 @@ class CompilerContainer {
               <label class="input-group-text border-0" for="versionSelector">Compiler</label>
             </div>
             ${this._view.versionSelector}
+            <div class="input-group-prepend">
+            </div>
+            ${this._view.evmVersionSelector}
           </header>
           ${this._view.compilationButton}
         </article>
@@ -189,6 +219,22 @@ class CompilerContainer {
     this.compileTabLogic.runCompiler()
   }
 
+  onchangeEvmVersion (_) {
+    let s = this._view.evmVersionSelector
+    let v = s.value
+    if (v === 'default') {
+      v = null
+    }
+    this.compileTabLogic.setEvmVersion(v)
+    if (!v) {
+      v = 'default'
+    }
+    const o = yo` <option disabled="disabled" selected="selected">EVM Version: ${v}</option>`
+    s.options[0] = o
+    s.selectedIndex = 0
+    // calling `runCompiler()` here would cause the UI to freeze with the selection drop down menu open
+  }
+
   onchangeLoadVersion (event) {
     this.data.selectedVersion = this._view.versionSelector.value
     this._updateVersionSelector()